3,109 research outputs found
Singlet Fermionic Dark Matter with Dark
We present a fermionic dark matter model mediated by the hidden gauge boson.
We assume the QED-like hidden sector which consists of a Dirac fermion and
U(1) gauge symmetry, and introduce an additional scalar electroweak doublet
field with the U(1) charge as a mediator. The hidden U(1) symmetry is
spontaneously broken by the electroweak symmetry breaking and there exists a
massive extra neutral gauge boson in this model which is the mediator between
the hidden and visible sectors. Due to the U(1) charge, the additional
scalar doublet does not couple to the Standard Model fermions, which leads to
the Higgs sector of type I two Higgs doublet model. The new gauge boson couples
to the Standard Model fermions with couplings proportional to those of the
ordinary boson but very suppressed, thus we call it the dark boson. We
study the phenomenology of the dark boson and the Higgs sector, and show
the hidden fermion can be the dark matter candidate.Comment: 10 pages, 3 figure
Phenomenology of a two-component dark matter model
We study a two-component dark matter model consisting of a Dirac fermion and
a complex scalar charged under new U(1) gauge group in the hidden sector. The
dark fermion plays the dominant component of dark matter which explains the
measured DM relic density of the Universe. It has no direct coupling to
ordinary standard model particles, thus evading strong constraints from the
direct DM detection experiments. The dark fermion is self-interacting through
the light dark gauge boson and it would be possible to address that this model
can be a resolution to the small scale structure problem of the Universe. The
light dark gauge boson, which interacts with the standard model sector, is also
stable and composes the subdominant DM component. We investigate the model
parameter space allowed by current experimental constraints and
phenomenological bounds. We also discuss the sensitivity of future experiments
such as SHiP, DUNE and ILC, for the obtained allowed parameter space.Comment: 13 pages, 1 figure, journal versio
Vacuum stability of conformally invariant scalar dark matter models
We discuss vacuum structure and vacuum stability in classically
scale-invariant renormalizable models with a scalar dark matter multiplet of
global O(N) symmetry together with an electroweak singlet scalar mediator. Our
conformally invariant scalar potential generates the electroweak symmetry
breaking via the Coleman-Weinberg mechanism, and the new scalar singlet
mediator acquires its mass through radiative corrections of the scalar dark
matters as well as of the standard model particles. Taking into account the
present collider bounds, we find the region of parameter space where the scalar
potential is stable and all the massless couplings are perturbative up to the
Planck scale. With the obtained parameter sets satisfying the vacuum stability
condition, we present the allowed region of new physics parameters satisfying
the recent measurement of relic abundance, and predict the elastic scattering
cross section of the new scalar multiplet into target nuclei for a direct
detection of the dark matter. We also discuss the collider signatures and
future discovery potentials of the new scalars.Comment: 11 pages, 6 figures (partly updated), journal version. arXiv admin
note: text overlap with arXiv:1904.1020
When and why to start continuous renal replacement therapy in critically ill patients with acute kidney injury
Acute kidney injury (AKI) is a common condition in critically ill patients, and may contribute to significant medical, social, and economic consequences, including death. Although there have been advances in medical technology, including continuous renal replacement therapy (CRRT), the mortality rate of AKI is high, and there is no fundamental treatment that can reverse disease progression. The decision to implement CRRT is often subjective and based primarily on the clinician’s judgment without consistent and concrete guidelines or protocols regarding when to initiate and discontinue CRRT and how to manage complications. Recently, several randomized controlled trials addressing the initiation of renal replacement therapy in critically ill patients with AKI have been completed, but clinical application of the findings is limited by the heterogeneity of the objectives and research designs. In this review, the advantages and disadvantages of CRRT initiation, clinical guideline recommendations, and the results of currently published clinical trials and meta-analyses are summarized to guide patient care and identify future research priorities
Why is asymptomatic bacteriuria overtreated?: A tertiary care institutional survey of resident physicians
Neutrophil extracellular traps and heparin-induced antibodies contribute to vascular access thrombosis in hemodialysis patients
Background Anti-heparin/platelet factor 4 (PF4) antibodies may trigger severe thrombotic complications in hemodialysis (HD) patients. Tetrameric PF4 has a high affinity for extracellular DNA, which is a key component of neutrophil extracellular traps (NETs); therefore, the interactions between anti-heparin/PF4 antibodies and NETs can contribute to prothrombotic events. Methods Anti-heparin/PF4 antibody levels were measured by enzyme-linked immunosorbent assay and an optical density > 1.8 was regarded as clinically significant. We additionally measured serum nucleosome levels as representative markers of NETs, and the contributions of anti-heparin/PF4 and increased serum nucleosome levels to the primary functional patency loss of vascular access was assessed. Results The frequency of anti-heparin/PF4 antibodies was significantly higher in incident HD patients compared to prevalent HD patients (23.6% vs. 7.7%). Serum nucleosome levels, as well as the white blood cell counts, neutrophil counts, and high- sensitivity C-reactive protein levels, were significantly higher in anti-heparin/PF4 antibody-positive patients compared to the control. Platelet counts tended to be lower in the patients with anti-heparin/PF4 of >1.8 than in the controls. Relative risk calculations showed that the presence of anti-heparin/PF4 antibodies increased the risk of primary functional patency failure by 4.28-fold, and this risk increased further with higher nucleosome levels. Furthermore, in the anti-heparin/PF4 antibody-positive group, the time to first vascular intervention was much shorter, and the risk of repeated intervention was higher, compared to the controls. Conclusion In incident HD patients, the presence of anti-heparin/PF4 antibodies was associated with increased NET formation; this could be a strong predictor of vascular access complication
High-flow arteriovenous fistula and myocardial fibrosis in hemodialysis patients with non-contrast cardiac magnetic resonance imaging
BackgroundThe role of high-flow arteriovenous fistula (AVF) in cardiovascular morbidity in hemodialysis (HD) patients is very likely under-recognized. We assessed the relationship between high access flow (Qa) and myocardial fibrosis in HD patients.MethodsMyocardial fibrosis was assessed by native T1 relaxation times on non-contrast cardiac magnetic resonance imaging and a potential marker of fibrosis. Serum levels of galectin-3, N-terminal pro-B-type natriuretic peptide (NT-proBNP), and monocyte chemoattractant protein 1 (MCP-1) were measured in 101 HD patients who underwent regular monitoring of AVF Qa. A high-flow AVF was defined as a Qa >2 L/min.ResultsHemodialysis patients showed significantly higher galectin-3 value and increased T1 relaxation time compared to healthy volunteers, suggesting increased myocardial fibrosis in uremic cardiomyopathy. In HD patients, 20 (19.8%) had a Qa > 2L/min, and they had significantly higher cardiac output, cardiac index, left ventricular mass, and increased T1 times than those with a Qa ≤ 2 L/min. Also, serum galectin-3 and NT-proBNP levels were much higher in the high Qa group, indicating a close relationship between the high Qa, increased myocardial fibrosis, and the risk of heart failure (HF) in HD patients. It is interesting that a higher AVF Qa for myocardial fibrosis was independent of several traditional cardiovascular risk factors as well as serum levels of NT-proBNP and MCP-1.ConclusionsA supra-physiologically high Qa can be related to myocardial fibrosis and increased risk of HF in HD patients. Regular Qa monitoring could allow early detection of a high-flow AVF that could arise cardiac complications
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