194 research outputs found
Boosted dark matter from a phantom fluid
It is known that theories of phantom dark energy, considered as quantum
fields, predict a continuous production of positive- plus negative-energy
particles, from spontaneous decay of the vacuum. We show that this can be a new
source of boosted dark matter or radiation, with consequences for direct
detection. We set constraints on such models using data from the XENONnT
experiment, and we show that recent excess events reported by the DAMIC
experiment can be consistently described as coming from dark radiation,
produced by vacuum decay, interacting with electrons.Comment: 4 pages, 2 figure
Phantom fluid cosmology: impact of a phantom hidden sector on cosmological observables
Phantom scalar theories are widely considered in cosmology, but rarely at the
quantum level, where they give rise to negative-energy ghost particles. These
cause decay of the vacuum into gravitons and photons, violating observational
gamma-ray limits unless the ghosts are effective degrees of freedom with a
cutoff at the few-MeV scale. We update the constraints on this scale,
finding that MeV. We further explore the possible
coupling of ghosts to a light, possibly massless, hidden sector particle, such
as a sterile neutrino. Vacuum decays can then cause the dark matter density of
the universe to grow at late times. The combined phantom plus dark matter fluid
has an effective equation of state , and functions as a new source of
dark energy. We derive constraints from cosmological observables on the rate of
vacuum decay into such a phantom fluid. We find a mild preference for the ghost
model over the standard cosmological one, and a modest amelioration of the
Hubble and tensions.Comment: 36 pages, 20 figure
Terahertz dipole nanoantenna arrays: resonance characteristics
Resonant dipole nanoantennas promise to considerably improve the capabilities of terahertz spectroscopy, offering the possibility of increasing its sensitivity through local field enhancement, while in principle allowing unprecedented spatial resolutions, well below the diffraction limit. Here, we investigate the resonance properties of ordered arrays of terahertz dipole nanoantennas, both experimentally and through numerical simulations. We demonstrate the tunability of this type of structures, in a range (∼1–2 THz) that is particularly interesting and accessible by means of standard zinc telluride sources. We additionally study the near-field resonance properties of the arrays, finding that the resonance shift observed between near-field and far-field spectra is predominantly ascribable to ohmic damping
The prevalence of resistant arterial hypertension and secondary causes in a cohort of hypertensive patients: a single center experience
The prevalence of resistant hypertension (RHT) still remains unknown. Aim of the study was to investigate in a large cohort of hypertensive patients the prevalence of RHT, and to identify in these patients the secondary forms of arterial hypertension (SH). We enrolled a series of 3685 consecutive hypertensive patients. All patients underwent complete physical examination, laboratory tests, screening for SH. Ambulatory blood pressure monitoring (ABPM) was performed to exclude white-coat hypertension. Further, we investigated for any obstructive sleep apnea syndrome (OSA). Only 232 (5.8%) hypertensive patients fulfilled criteria for RHT. 91 (39%) had a SH; 56 (61%) hypertensive patients had a primary aldosteronism, 22 (24%) had OSA, 7 (7.7%) had a hypercortisolism, and 5 (5.5%) had a renovascular hypertension (RVH). Only one patient had adrenal pheochromocytoma. An accurate definition and investigation into RHT is needed. We recommend ABPM to all patients at diagnosis. Finally, all patients must be screened for SH, such as adrenal hypertension, OSA and RVH, especially those who are apparently resistant to polypharmacological treatment
Extremely large extinction efficiency and field enhancement in terahertz resonant dipole nanoantennas
The distinctive ability of nanometallic structures to manipulate light at the nanoscale has recently promoted their use for a spectacular set of applications in a wide range of areas of research including artificial optical materials, nano-imaging, biosensing, and nonlinear optics. Here we transfer this concept to the terahertz spectral region, demonstrating a metal nanostructure in shape of a dipole nanoantenna, which can efficiently resonate at terahertz frequencies, showing an effective cross section >100 times larger than its geometrical area, and a field enhancement factor of ~280, confined on a lateral section of ~λ/1,000. These results lead to immediate applications in terahertz artificial materials exhibiting giant dichroism, suggest the use of dipole nanoantennas in nanostructure-based terahertz metamaterials, and pave the way for nanoantenna-enhanced terahertz few-molecule spectroscopy and localized terahertz nonlinear optics
Biofilm is a major virulence determinant in bacterial colonization of chronic skin ulcers independently from the multidrug resistant phenotype
Bacterial biofilm is a major factor in delayed wound healing and high levels of biofilm production have been repeatedly described in multidrug resistant organisms (MDROs). Nevertheless, a quantitative correlation between biofilm production and the profile of antimicrobial drug resistance in delayed wound healing remains to be determined. Microbial identification, antibiotic susceptibility and biofilm production were assessed in 135 clinical isolates from 87 patients. Gram-negative bacteria were the most represented microorganisms (60.8%) with MDROs accounting for 31.8% of the total isolates. Assessment of biofilm production revealed that 80% of the strains were able to form biofilm. A comparable level of biofilm production was found with both MDRO and not-MDRO with no significant differences between groups. All the methicillin-resistant Staphylococcus aureus (MRSA) and 80% of Pseudomonas aeruginosa MDR strains were found as moderate/high biofilm producers. Conversely, less than 17% of Klebsiella pneumoniae extended-spectrum beta-lactamase (ESBL), Escherichia coli-ESBL and Acinetobacter baumannii were moderate/high biofilm producers. Notably, those strains classified as non-biofilm producers, were always associated with biofilm producer bacteria in polymicrobial colonization. This study shows that biofilm producers were present in all chronic skin ulcers, suggesting that biofilm represents a key virulence determinant in promoting bacterial persistence and chronicity of ulcerative lesions independently from the MDRO phenotype
Dibattito su Storie di imprese
Storie di imprese (TAO Digital Library, 2010), dedicated to the organizational transformations of five enterprises (Fiat Auto, Finmeccanica, Ciba Specialty chemicals, Zurich, Poste Italiane) during the 2000-2010 decade, stimulated a wide debate. This publication, which collects the commentaries and discussions of three seminar that took place in different Universities with the participation of scholars from different disciplines, continues the reflection about the crucial question: How do enterprises change
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