3,786 research outputs found
On the shape of tachyons
We study some aspects of the experimental behaviour of tachyons, in particular by finding out their « apparent » shape. A Superluminal particle, which in its own rest frame is spherical or ellipsoidal (and with an infinite lifetime), would « appear » to a laboratory frame as occupying the whole region of space bound by a double cone and a twosheeted hyperboloid. Such a structure (the tachyon « shape ») rigidly travels with the speed of the tachyon. However, if the Superluminal particle has a finite lifetimein its rest frame, then in the laboratory frame it gets afinite space extension. As a by-product, we are able to interpret physically the imaginary units entering—as is well known—the transverse co-ordinates in the Superluminal Lorentz transformations. The various particular or limiting cases of the tachyon shape are thoroughly considered. Finally, some brief considerations concerning possible experiments to look for tachyons are added
Performance of Optically Readout GEM-based TPC with a 55Fe source
Optical readout of large Time Projection Chambers (TPCs) with multiple Gas
Electron Multipliers (GEMs) amplification stages has shown to provide very
interesting performances for high energy particle tracking. Proposed
applications for low-energy and rare event studies, such as Dark Matter search,
ask for demanding performance in the keV energy range. The performance of such
a readout was studied in details as a function of the electric field
configuration and GEM gain by using a Fe source within a 7 litre
sensitive volume detector developed as a part of the R\&D for the CYGNUS
project. Results reported in this paper show that the low noise level of the
sensor allows to operate with a 2~keV threshold while keeping a rate of
fake-events lesser than 10 per year. In this configuration, a detection
efficiency well above 95\% along with an energy resolution () of 18\%
is obtained for the 5.9 keV photons, demonstrating the very promising
capabilities of this technique
Validation of the Modena bleeding score in endoscopic sinus surgery
Introduction: The Modena bleeding score is a categorical rating scale that allows the assessment of the surgical field in relation to bleeding during endoscopic surgery. It has recently been presented and validated in the field of endoscopic ear surgery by the present authors. The Modena bleeding score provides five grades for rating the surgical field during endoscopic procedures (from grade 1 − no bleeding to grade 5 − bleeding that prevents every surgical procedure except those dedicated to bleeding control). Objective: The aim of this study was to validate the Modena bleeding score in the setting of endoscopic sinus surgery. Methods: Fifteen three-minute videos of endoscopic sinus surgery procedures (each containing three bleeding situations) were evaluated by 15 specialists, using the Modena bleeding score. Intra and inter-rater reliability were assessed, and the clinical validity of the Modena bleeding score was calculated using a referent standard. Results: The data analysis showed an intra-rater reliability ranging from 0.6336 to 0.861. The inter-rater reliability ranged from 0.676 to 0.844. The clinical validity was α = 0.70; confidence limits: 0.64 − 0.75, corresponding to substantial agreement. Conclusion: The Modena bleeding score is an effective method to score bleeding during endoscopic sinus surgery. Its application in future research could facilitate the performance and efficacy assessment of surgical techniques, materials or devices aimed to bleeding control during endoscopic sinus surgery
Plasma fibrinogen: now also an antidepressant response marker?
Major depressive disorder (MDD) is one of the leading causes of global disability. It is a risk factor for noncompliance with medical treatment, with about 40% of patients not responding to currently used antidepressant drugs. The identification and clinical implementation of biomarkers that can indicate the likelihood of treatment response are needed in order to predict which patients will benefit from an antidepressant drug. While analyzing the blood plasma proteome collected from MDD patients before the initiation of antidepressant medication, we observed different fibrinogen alpha (FGA) levels between drug responders and nonresponders. These results were replicated in a second set of patients. Our findings lend further support to a recently identified association between MDD and fibrinogen levels from a large-scale study
Stage-variations of anandamide hydrolase activity in the mouse uterus during the natural oestrus cycle
Recent studies have demonstrated that the endogenous cannabinoids are important modulators of fertility in mammals. In particular, a role of the endocannabinoid system in early stages of embryo development, oviductal transport of embryos, pregnancy maintenance and labour has been demonstrated in rodents and/or in humans. In the present paper, we report the analysis of FAAH activity and protein content in the mouse uterus as a function of the natural oestrus cycle stages. Variations of FAAH activity are discussed in relationship to changes in sex steroid levels and to the possible action of AEA on remodelling of uterine tissues
Non-cell-autonomous regulation of interneuron specification mediated by extracellular vesicles
Disruption in neurogenesis and neuronal migration can influence the assembly of cortical circuits, affecting the excitatory-inhibitory balance and resulting in neurodevelopmental and neuropsychiatric disorders. Using ventral cerebral organoids and dorsoventral cerebral assembloids with mutations in the extracellular matrix gene LGALS3BP, we show that extracellular vesicles released into the extracellular environment regulate the molecular differentiation of neurons, resulting in alterations in migratory dynamics. To investigate how extracellular vesicles affect neuronal specification and migration dynamics, we collected extracellular vesicles from ventral cerebral organoids carrying a mutation in LGALS3BP, previously identified in individuals with cortical malformations and neuropsychiatric disorders. These results revealed differences in protein composition and changes in dorsoventral patterning. Proteins associated with cell fate decision, neuronal migration, and extracellular matrix composition were altered in mutant extracellular vesicles. Moreover, we show that treatment with extracellular vesicles changes the transcriptomic profile in neural progenitor cells. Our results indicate that neuronal molecular differentiation can be influenced by extracellular vesicles
Search for galactic axions with a high-Q dielectric cavity
A haloscope of the QUAX-- experiment, composed of an high-Q resonant
cavity immersed in a 8 T magnet and cooled to ~K is operated to
search for galactic axion with mass . The design of
the cavity with hollow dielectric cylinders concentrically inserted in a OFHC
Cu cavity, allowed us to maintain a loaded quality-factor Q
during the measurements in presence of magnetic field. Through the cavity
tuning mechanism it was possible to modulate the resonance frequency of the
haloscope in the region ~GHz and thus acquire different
dataset at different resonance frequencies. Acquiring each dataset for about 50
minutes, combining them and correcting for the axion's signal
estimation-efficiency we set a limit on the axion-photon coupling
GeV with the confidence level
set at
High quality factor photonic cavity for dark matter axion searches
Searches for dark matter axion involve the use of microwave resonant cavities
operating in a strong magnetic field. Detector sensitivity is directly related
to the cavity quality factor, which is limited, however, by the presence of the
external magnetic field. In this paper we present a cavity of novel design
whose quality factor is not affected by a magnetic field. It is based on a
photonic structure by the use of sapphire rods. The quality factor at cryogenic
temperature is in excess of for a selected mode.Comment: 6 pages, 7 figure
- …