33,615 research outputs found
Eye movement patterns during the recognition of three-dimensional objects: Preferential fixation of concave surface curvature minima
This study used eye movement patterns to examine how high-level shape information is used during 3D object recognition. Eye movements were recorded while observers either actively memorized or passively viewed sets of novel objects, and then during a subsequent recognition memory task. Fixation data were contrasted against different algorithmically generated models of shape analysis based on: (1) regions of internal concave or (2) convex surface curvature discontinuity or (3) external bounding contour. The results showed a preference for fixation at regions of internal local features during both active memorization and passive viewing but also for regions of concave surface curvature during the recognition task. These findings provide new evidence supporting the special functional status of local concave discontinuities in recognition and show how studies of eye movement patterns can elucidate shape information processing in human vision
Annual rings in a native Hawaiian tree, Sophora chrysophylla, on Maunakea, Hawaiʻi
Annual rings are not commonly produced in tropical trees because they grow in a relatively aseasonal environment. However, in the subalpine zones of Hawaiʻi's highest volcanoes, there is often strong seasonal variability in temperature and rainfall. Using classical dendrochronological methods, annual growth rings were shown to occur in Sophora chrysophylla, a native tree species on Maunakea, Hawaiʻi. Chronologies were established from nearby non-native, live conifer trees and these were used to verify the dates from a total of 52 series from 22 S. chrysophylla trees, establishing an 86-y chronology (1926–2011). Ring-width patterns were significantly correlated with monthly rainfall from August of the previous year. This study is the first in the eastern tropical Pacific region to demonstrate annual growth rings in trees.postprin
Growth and dislocation studies of β-HMX
Background: The defect structure of organic materials is important as it plays a major role in their crystal growth
properties. It also can play a subcritical role in “hot-spot” detonation processes of energetics and one such
energetic is cyclotetramethylene-tetranitramine, in the commonly used beta form (β-HMX).
Results: The as-grown crystals grown by evaporation from acetone show prismatic, tabular and columnar habits, all
with {011}, {110}, (010) and (101) faces. Etching on (010) surfaces revealed three different types of etch pits, two of
which could be identified with either pure screw or pure edge dislocations, the third is shown to be an artifact of
the twinning process that this material undergoes. Examination of the {011} and {110} surfaces show only one type
of etch pit on each surface; however their natural asymmetry precludes the easy identification of their Burgers
vector or dislocation type. Etching of cleaved {011} surfaces demonstrates that the etch pits can be associated with
line dislocations. All dislocations appear randomly on the crystal surfaces and do not form alignments characteristic
of mechanical deformation by dislocation slip.
Conclusions: Crystals of β-HMX grown from acetone show good morphological agreement with that predicted by
modelling, with three distinct crystal habits observed depending upon the supersaturation of the growth solution.
Prismatic habit was favoured at low supersaturation, while tabular and columnar crystals were predominant at
higher super saturations. The twin plane in β-HMX was identified as a (101) reflection plane. The low plasticity of
β-HMX is shown by the lack of etch pit alignments corresponding to mechanically induced dislocation arrays.
On untwinned {010} faces, two types of dislocations exist, pure edge dislocations with b = [010] and pure screw
dislocations with b = [010]. On twinned (010) faces, a third dislocation type exists and it is proposed that these pits
are associated with pure screw dislocations with b = [010]
Variability and uncertainty in empirical ground-motion prediction for probabilistic hazard and risk analyses
© The Author(s) 2015.The terms aleatory variability and epistemic uncertainty mean different things to people who routinely use them within the fields of seismic hazard and risk analysis. This state is not helped by the repetition of loosely framed generic definitions that actually inaccurate. The present paper takes a closer look at the components of total uncertainty that contribute to ground-motion modelling in hazard and risk applications. The sources and nature of uncertainty are discussed and it is shown that the common approach to deciding what should be included within hazard and risk integrals and what should be pushed into logic tree formulations warrants reconsideration. In addition, it is shown that current approaches to the generation of random fields of ground motions for spatial risk analyses are incorrect and a more appropriate framework is presented
A Fast Algorithm for Robust Regression with Penalised Trimmed Squares
The presence of groups containing high leverage outliers makes linear
regression a difficult problem due to the masking effect. The available high
breakdown estimators based on Least Trimmed Squares often do not succeed in
detecting masked high leverage outliers in finite samples.
An alternative to the LTS estimator, called Penalised Trimmed Squares (PTS)
estimator, was introduced by the authors in \cite{ZiouAv:05,ZiAvPi:07} and it
appears to be less sensitive to the masking problem. This estimator is defined
by a Quadratic Mixed Integer Programming (QMIP) problem, where in the objective
function a penalty cost for each observation is included which serves as an
upper bound on the residual error for any feasible regression line. Since the
PTS does not require presetting the number of outliers to delete from the data
set, it has better efficiency with respect to other estimators. However, due to
the high computational complexity of the resulting QMIP problem, exact
solutions for moderately large regression problems is infeasible.
In this paper we further establish the theoretical properties of the PTS
estimator, such as high breakdown and efficiency, and propose an approximate
algorithm called Fast-PTS to compute the PTS estimator for large data sets
efficiently. Extensive computational experiments on sets of benchmark instances
with varying degrees of outlier contamination, indicate that the proposed
algorithm performs well in identifying groups of high leverage outliers in
reasonable computational time.Comment: 27 page
Shear waves induced by moving needle in MR Elastography
Magnetic Resonance Elastography (MRE) is a phase contrast-based method for observing shear wave propagation in a material to determine its stiffness. The objective of this study was to determine whether shear waves suitable for MRE can be induced using a moving acupuncture needle. Tissue-simulating bovine gel phantom and a 0.4mm diameter acupuncture needle were used in the experiment. The results showed that observable shear waves could be induced in the gel phantom by cyclic needle motion. The observed wavelength varied with excitation frequency, as expected. Generating shear waves using moving needles may be a useful tool to study the basic mechanism of acupuncture with MRE. Further study will be conducted to observe the wave motion in inhomogeneous media and acupuncture-induced effects in invivo studies.published_or_final_versio
Adeno-tonsillectomy and rapid maxillary distraction in pre-pubertal children: a pilot study
Introduction When both narrow maxilla and moderately
enlarged tonsils are present in children with obstructive
sleep apnea, the decision of which treatment to do first is
unclear. A preliminary randomized study was done to
perform a power analysis and determine the number of
subjects necessary to have an appropriate response. Thirtyone
children, 14 boys, diagnosed with OSA based on
clinical symptoms and polysomnography (PSG) findings
had presence of both narrow maxillary complex and
enlarged tonsils. They were scheduled to have both
adeno-tonsillectomy and RME for which the order of
treatment was randomized: group 1 received surgery
followed by orthodontics, while group 2 received
orthodontics followed by surgery. Each child was seen
by an ENT, an orthodontist, and a sleep medicine
specialist. The validated pediatric sleep questionnaire
and PSG were done at entry and after each treatment
phase at time of PSG. Statistical analyses were ANOVA
repeated measures and t tests.
Results The mean age of the children at entry was 6.5±
0.2 years (mean ± SEM). Overall, even if children
presented improvement of both clinical symptoms and
PSG findings, none of the children presented normal
results after treatment 1, at the exception of one case.
There was no significant difference in the amount of
improvement noted independently of the first treatment
approach. Thirty children underwent treatment 2, with an
overall significant improvement shown for PSG findings
compared to baseline and compared to treatment 1,
without any group differences.
Conclusion This preliminary study emphasizes the need to
have more than subjective clinical scales for determination
of sequence of treatments
Anti-inflammation activity and chemical composition of flower essential oil from Hedychium coronarium
Hedychium coronarium Koen. (Family Zingiberaceae), popularly named butterfly ginger, is widely available in tropical and subtropical regions. It has been used in folk medicine for many conditions, such as contusion inflammation, anti-rheumatic and so on. In this study, chemical compositions and anti-inflammatory activity of this flowers’ essential oil were investigated for the first time. Followed by GC–MS analysis, a total of 29 components were identified and the main constituents included -transocimenone (28.05%), linalool (18.52%), 1,8-cineole (11.35%), -terpineol (7.11%), 10-epi--eudesmol (6.06%), sabinene (4.59%) and terpinen-4-ol (3.17%). We measured the antioxidant activity of the essential oil in vitro (DPPH reduction assay and ferric reducing antioxidant power assay) and the antiinflammatory activity in vivo (carrageenan-induced hind paw edema in rats). The oil (100 mg/kg p.o.) produced significant inhibition of paw oedema, but showed poor antioxidant activity (with the DPPH IC50 value of 1091.00 g/ml and FRAP value of 0.22 mol Fe2+/mg). The results reveal that there is no direct correlation between anti-inflammatory effect and antioxidant activity of this essential oil
Is the sigma-1 receptor a potential pharmacological target for cardiac pathologies? A systematic review.
Sigma-1 receptors are ligand-regulated chaperone proteins, involved in several cellular mechanisms. The aim of this systematic review was to examine the effects that the sigma-1 receptor has on the cardiovascular system. The interaction targets and proposed mechanisms of action of sigma-1 receptors were explored, with the aim of determining if the sigma-1 receptor is a potential pharmacological target for cardiac pathologies. This systematic review was conducted according to the PRISMA guidelines and these were used to critically appraise eligible studies. Pubmed and Scopus were systematically searched for articles investigating sigma-1 receptors in the cardiovascular system. Papers identified by the search terms were then subject to analysis against pre-determined inclusion criteria. 23 manuscripts met the inclusion criteria and were included in this review. The experimental platforms, experimental techniques utilised and the results of the studies were summarised. The sigma-1 receptor is found to be implicated in cardioprotection, via various mechanisms including stimulating the Akt-eNOS pathway, and reduction of Ca2Â +Â leakage into the cytosol via modulating certain calcium channels. Sigma-1 receptors are also found to modulate other cardiac ion channels including different subtypes of potassium and sodium channels and have been shown to modulate intracardiac neuron excitability. The sigma-1 receptor is a potential therapeutic target for treatment of cardiac pathologies, particularly cardiac hypertrophy. We therefore suggest investigating the cardioprotective mechanisms of sigma-1 receptor function, alongside proposed potential ligands that can stimulate these functions
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