2,142 research outputs found
Is a Trineutron Resonance Lower in Energy than a Tetraneutron Resonance?
We present quantum Monte Carlo calculations of few-neutron systems confined
in external potentials based on local chiral interactions at
next-to-next-to-leading order in chiral effective field theory. The energy and
radial densities for these systems are calculated in different external
Woods-Saxon potentials. We assume that their extrapolation to zero
external-potential depth provides a quantitative estimate of three- and
four-neutron resonances. The validity of this assumption is demonstrated by
benchmarking with an exact diagonalization in the two-body case. We find that
the extrapolated trineutron resonance, as well as the energy for shallow well
depths, is lower than the tetraneutron resonance energy. This suggests that a
three-neutron resonance exists below a four-neutron resonance in nature and is
potentially measurable. To confirm that the relative ordering of three- and
four-neutron resonances is not an artifact of the external confinement, we test
that the odd-even staggering in the helium isotopic chain is reproduced within
this approach. Finally, we discuss similarities between our results and
ultracold Fermi gases.Comment: 6 pages, 5 figures, version compatible with published lette
Genetic differentiation and hybridization in two naturally occurring sympatric trout Salmo spp. forms from a small karstic lake.
In this study, multiple molecular markers [genotyping of 12 nuclear microsatellite loci and the
protein-coding gene ldh-c1 * plus sequencing of the mitochondrial DNA (mtDNA) control region]
were employed to investigate the genetic structure of the two trout forms, Salmo cettii and Salmo
fibreni , inhabiting Lake Posta Fibreno, central Italy. The two forms were found to share a unique
mtDNA haplotype, belonging to a widespread Mediterranean haplogroup (AD). Bayesian clustering
analyses showed that these two forms correspond to well-defined autochthonous gene pools. Genetic
introgression between the two gene pools, however, was observed, whose frequency appears to
correlate with the environmental features of the spawning sites. The interplay of selection for the
spawning sites, philopatry and natural selection can be argued to maintain genetic differentiation
despite the lack of complete reproductive isolation
Spectroscopic and morphological data assessing the apatite forming ability of calcium hydroxide-releasing materials for pulp capping
A pulp capping material must perform as a barrier and protect the dental pulpal complex by inducing the formation of a new dentin bridge or dentin-like tissue. Being a favorable condition for the healing process, the apatite forming ability of TheraCal (light-curable Portland-dimethacrylate cement) and Dycal (calcium hydroxide-based) pulp capping materials was studied in two simulated body fluids, i.e. Dulbecco's Phosphate Buffered Saline (DPBS) and Hank's Balanced Salt Solution (HBSS). The cements were analyzed before and after soaking in these media for different times (1\u201328 days) by ESEM-EDX, micro-Raman and IR spectroscopy. This data article refers to \u201cAn in vitro study on dentin demineralization and remineralization: collagen rearrangements and influence on the enucleated phase\u201d (Di Foggia et al., 2019)
Theta-frequency resonance at the cerebellum input stage improves spike timing on the millisecond time-scale
The neuronal circuits of the brain are thought to use resonance and oscillations to improve communication over specific frequency bands (Llinas, 1988; Buzsaki, 2006). However, the properties and mechanism of these phenomena in brain circuits remain largely unknown. Here we show that, at the cerebellum input stage, the granular layer (GRL) generates its maximum response at 5\u20137 Hz both in vivo following tactile sensory stimulation of the whisker pad and in acute slices following mossy fiber bundle stimulation. The spatial analysis of GRL activity performed using voltage-sensitive dye (VSD) imaging revealed 5\u20137 Hz resonance covering large GRL areas. In single granule cells, resonance appeared as a reorganization of output spike bursts on the millisecond time-scale, such that the first spike occurred earlier and with higher temporal precision and the probability of spike generation increased. Resonance was independent from circuit inhibition, as it persisted with little variation in the presence of the GABAA receptor blocker, gabazine. However, circuit inhibition reduced the resonance area more markedly at 7 Hz. Simulations with detailed computational models suggested that resonance depended on intrinsic granule cells ionic mechanisms: specifically, Kslow (M-like) and KA currents acted as resonators and the persistent Na current and NMDA current acted as amplifiers. This form of resonance may play an important role for enhancing coherent spike emission from the GRL when theta-frequency bursts are transmitted by the cerebral cortex and peripheral sensory structures during sensory-motor processing, cognition, and learning
Confirmation of an exoplanet using the transit color signature: Kepler-418b, a blended giant planet in a multiplanet system
We announce confirmation of Kepler-418b, one of two proposed planets in this
system. This is the first confirmation of an exoplanet based primarily on the
transit color signature technique. We used the Kepler public data archive
combined with multicolor photometry from the Gran Telescopio de Canarias and
radial velocity follow-up using FIES at the Nordic Optical Telescope for
confirmation. We report a confident detection of a transit color signature that
can only be explained by a compact occulting body, entirely ruling out a
contaminating eclipsing binary, a hierarchical triple, or a grazing eclipsing
binary. Those findings are corroborated by our radial velocity measurements,
which put an upper limit of ~1 Mjup on the mass of Kepler-418b. We also report
that the host star is significantly blended, confirming the ~10% light
contamination suspected from the crowding metric in the Kepler light curve
measured by the Kepler team. We report detection of an unresolved light source
that contributes an additional ~40% to the target star, which would not have
been detected without multicolor photometric analysis. The resulting
planet-star radius ratio is 0.110 +/- 0.0025, more than 25% more than the 0.087
measured by Kepler, leading to a radius of 1.20 +/- 0.16 Rjup instead of the
0.94 Rjup measured by the Kepler team. This is the first confirmation of an
exoplanet candidate based primarily on the transit color signature,
demonstrating that this technique is viable from ground for giant planets. It
is particularly useful for planets with long periods such as Kepler-418b, which
tend to have long transit durations. Additionally, multicolor photometric
analysis of transits can reveal unknown stellar neighbors and binary companions
that do not affect the classification of the transiting object but can have a
very significant effect on the perceived planetary radius.Comment: accepted by Astronomy & Astrophysic
Bilateral Severe Corneal Ulcer in a Patient with Lung Adenocarcinoma Treated with Gefitinib
We describe the case of Gefitinib-related bilateral corneal perforation. An 86-year-old female patient had bilateral painless and progressive vision loss due to neurotrophic corneal ulcer, following a 2-month treatment with Gefitinib, a selective epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor for metastatic adenocarcinoma of the lung with confirmed EGFR gene mutation. She had no signs of ocular infection, inflammation, or lid problems to account for the development of corneal damage. Neurotrophic ulcer evolved into a frank perforation in one eye and an impending perforation on the other eye. EGFR inhibitors have been associated with dry eye, epithelial erosions, ulcerative keratitis, and corneal edema. However, to the best of our knowledge, this is the first case of bilateral severe corneal ulcer due to Gefitinib. The patient went on to have bilateral corneal graft surgery. This case aims to raise awareness among ophthalmologists and oncologists of the association between EGFR inhibitors, corneal neurotrophic ulcers, and possible evolution in corneal perforation
Zero Temperature Dynamics of 2D and 3D Ising Ferromagnets
We consider zero-temperature, stochastic Ising models with nearest-neighbor
interactions in two and three dimensions. Using both symmetric and asymmetric
initial configurations, we study the evolution of the system with time. We
examine the issue of convergence of the dynamics and discuss the nature of the
final state of the system. By determining a relation between the median number
of spin flips per site, the probability p that a spin in the initial spin
configuration takes the value +1, and lattice size, we conclude that in two and
three dimensions, the system converges to a frozen (but not necessarily
uniform) state when p is not equal to 1/2. Results for p=1/2 in three
dimensions are consistent with the conjecture that the system does not evolve
towards a fully frozen limiting state. Our simulations also uncover `striped'
and `blinker' states first discussed by Spirin et al., and their statistical
properties are investigated.Comment: 17 pages, 12 figure
Scattering Compensation for Deep Brain Microscopy: The Long Road to Get Proper Images
Multiphoton microscopy is the most widespread method for preclinical brain imaging when sub-micrometer resolution is required. Nonetheless, even in the case of optimal experimental conditions, only a few hundred micrometers under the brain surface can be imaged by multiphoton microscopy. The main limitation preventing the acquisition of images from deep brain structures is the random light scattering which, until recently, was considered an unsurmountable obstacle. When in 2007 a breakthrough work by Vellekoop and Mosk [1] proved it is indeed possible to compensate for random scattering by using high resolution phase modulators, the neuro-photonics community started chasing the dream of a multiphoton microscopy capable of reaching arbitrary depths within the brain. Unfortunately, more than 10 years later, despite a massive improvement of technologies for scattering compensation in terms of speed, performances and reliability, clear images from deep layers of biological tissues are still lacking. In this work, we review recent technological and methodological advances in the field of multiphoton microscopy analyzing the big issue of scattering compensation. We will highlight the limits hampering image acquisition, and we will try to analyze the road scientists must tackle to target one of the most challenging issue in the field of biomedical imaging
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