15,730 research outputs found
A Brief Review on Syntheses, Structures and Applications of Nanoscrolls
Nanoscrolls are papyrus-like nanostructures which present unique properties
due to their open ended morphology. These properties can be exploited in a
plethora of technological applications, leading to the design of novel and
interesting devices. During the past decade, significant advances in the
synthesis and characterization of these structures have been made, but many
challenges still remain. In this mini review we provide an overview on their
history, experimental synthesis methods, basic properties and application
perspectives
Investigating the inclusive transverse spectra in high-energy collisions in the context of geometric scaling framework
The presence of geometric scaling within the spectra of produced
hadrons at high energy collisions using small- -factorization is
investigated. It is proposed a phenomenological parameterization for the
unintegrated gluon distribution in the scaling range which reproduces the
features of the differential cross section both in the saturated and dilute
perturbative QCD regimes. As the saturation scale acts as an effective
regulator of the infrared region (IR), the extension of the model to quantities
usually associated to soft physics is studied. The approach is applied to
compute the average and the rapidity distribution of produced gluons at
high energies.Comment: 11 pages, 9 figure
Darth Fader: Using wavelets to obtain accurate redshifts of spectra at very low signal-to-noise
We present the DARTH FADER algorithm, a new wavelet-based method for
estimating redshifts of galaxy spectra in spectral surveys that is particularly
adept in the very low SNR regime. We use a standard cross-correlation method to
estimate the redshifts of galaxies, using a template set built using a PCA
analysis on a set of simulated, noise-free spectra. Darth Fader employs wavelet
filtering to both estimate the continuum & to extract prominent line features
in each galaxy spectrum. A simple selection criterion based on the number of
features present in the spectrum is then used to clean the catalogue: galaxies
with fewer than six total features are removed as we are unlikely to obtain a
reliable redshift estimate. Applying our wavelet-based cleaning algorithm to a
simulated testing set, we successfully build a clean catalogue including
extremely low signal-to-noise data (SNR=2.0), for which we are able to obtain a
5.1% catastrophic failure rate in the redshift estimates (compared with 34.5%
prior to cleaning). We also show that for a catalogue with uniformly mixed SNRs
between 1.0 & 20.0, with realistic pixel-dependent noise, it is possible to
obtain redshifts with a catastrophic failure rate of 3.3% after cleaning (as
compared to 22.7% before cleaning). Whilst we do not test this algorithm
exhaustively on real data, we present a proof of concept of the applicability
of this method to real data, showing that the wavelet filtering techniques
perform well when applied to some typical spectra from the SDSS archive. The
Darth Fader algorithm provides a robust method for extracting spectral features
from very noisy spectra. The resulting clean catalogue gives an extremely low
rate of catastrophic failures, even when the spectra have a very low SNR. For
very large sky surveys, this technique may offer a significant boost in the
number of faint galaxies with accurately determined redshifts.Comment: 22 pages, 15 figures. Accepted for publication in Astronomy &
Astrophysic
Quantum phase transition triggering magnetic BICs in graphene
Graphene hosting a pair of collinear adatoms in the phantom atom
configuration has pseudogap with cubic scaling on energy,
which leads to the appearance of
spin-degenerate bound states in the continuum (BICs) [Phys. Rev. B 92, 045409
(2015)]. In the case when adatoms are locally coupled to a single carbon atom
the pseudogap scales linearly with energy, which prevents the formation of
BICs. In this Letter, we explore the effects of non-local coupling
characterized by the Fano factor of interference tunable by changing
the slope of the Dirac cones in the graphene band-structure. We demonstrate
that three distinct regimes can be identified: i) for (critical
point) a mixed pseudogap appears
yielding a phase with spin-degenerate BICs; ii) near when
the system undergoes a quantum phase
transition in which the new phase is characterized by magnetic BICs and iii) at
a second critical value the cubic scaling of the pseudogap with
energy characteristic to the phantom atom
configuration is restored and the phase with non-magnetic BICs is recovered.
The phase with magnetic BICs can be described in terms of an effective
intrinsic exchange field of ferromagnetic nature between the adatoms mediated
by graphene monolayer. We thus propose a new type of quantum phase transition
resulting from the competition between the states characterized by
spin-degenerate and magnetic BICs
GORLIN-GOLTZ SYNDROME: A CASE REPORT
Introdução: O Síndrome de Gorlin-Goltz é uma condição hereditária autossómica dominante rara caracterizada por: carcinomas basocelulares, queratoquistos odontogénicos, depressões palmo-plantares, calcificações da foice cerebral e malformações esqueléticas. Associa-se também a meduloblastoma e outras neoplasias.
Caso Clínico: Adolescente de 11 anos, com antecedentes de macrocefalia. Referenciada à consulta de estomatologia por quistos mandibulares recidivantes. O exame anátomo-patológico revelou tratarem-se de queratoquistos odontogénicos, pelo que é encaminhada para a consulta de pediatria. Objetivamente,
apresentava macrocefalia e facies “gros seiro” com bossas frontais e hipertelorismo. Efetuou estudo genético, que detetou mutação do gene PTCH1, confirmando a suspeita clínica.
Discussão: Os queratoquistos odontogénicos são o achado mais representativo do síndrome de Gorlin-Goltz nas duas primeiras décadas de vida, sendo de extrema importância um elevado índice de suspeição por parte do pediatra, com especial relevância para as alterações minor. Após o estabelecimento do
diagnóstico, é necessária uma equipa multidisciplinar para um adequado seguimento e tratamento atempado.Introduction: The Gorlin-Goltz syndrome is a rare autosomal dominant inherited condition characterized by: basal cell carcinomas, odontogenic keratocysts, palmar or plantar pits, calcification of the falx cerebri and skeletal malformations. Medulloblastoma and other tumors are also associated with it.
Case report: An 11-year-old female, with a history of macrocephaly, was referred to the Stomatology Department for recurrent mandibular cyst. Histopathological exam revealed odontogenic keratocysts, so the patient was referred to the Pediatric Department. Physical examination revealed macrocephaly and
coarse face, with frontal bossing and hy pertelorism. The genetic study performed detected a mutation in PTCH1 gene, confirming the clinical suspicion.
Discussion: Odontogenic keratocysts are the most representative finding in Gorlin-Goltz Syndrome in the first two decades of life, therefore a high suspicion level is mandatory among pediatricians concerning detection of minor changes. After the diagnosis, a multidisciplinary team is required for adequate follow-up and timely treatment
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