794 research outputs found
In Vivo Photoacoustic Imaging of Anterior Ocular Vasculature: A Random Sample Consensus Approach
Visualizing ocular vasculature is important in clinical ophthalmology because ocular circulation abnormalities are early signs of ocular diseases. Photoacoustic microscopy (PAM) images the ocular vasculature without using exogenous contrast agents, avoiding associated side effects. Moreover, 3D PAM images can be useful in understanding vessel-related eye disease. However, the complex structure of the multi-layered vessels still present challenges in evaluating ocular vasculature. In this study, we demonstrate a new method to evaluate blood circulation in the eye by combining in vivo PAM imaging and an ocular surface estimation method based on a machine learning algorithm: a random sample consensus algorithm. By using the developed estimation method, we were able to visualize the PA ocular vascular image intuitively and demonstrate layer-by-layer analysis of injured ocular vasculature. We believe that our method can provide more accurate evaluations of the eye circulation in ophthalmic applications. ? The Author(s) 2017.1110Ysciescopu
A UAV-Aided Real-Time Channel Sounder for Highly Dynamic Nonstationary A2G Scenarios
With the rapid development and broad applications of unmanned aerial vehicle (UAV)-based wireless stations in the sky, fundamental understanding and characterization of the realistic air-to-ground (A2G) communication link properties are crucial. In this article, a UAV-aided channel sounder with a real-time processing hardware system is developed for highly dynamic and nonstationary A2G channel measurements. In the hardware system, a global positioning system (GPS)-based triggering signal is designed, the equivalent antenna pattern affected by the UAV airframe is considered, and an appropriate sounding signal is selected, to improve the accuracy of measured channel impulse response (CIR). Moreover, real-time hardware processing algorithms for raw channel data, that is, CIR extraction, system response elimination (SRE), power loss recovery (PLR), and adaptive multipath component (MPC) recognition are developed and implemented on a single field-programmable gate array (FPGA) chip. In this way, the required storage size of channel data and the processing time for one slice of CIR is greatly decreased, which can meet the requirement of nonstationary A2G channel measurement with a high sampling rate and long-time measurement. A commercial channel emulator is used to reproduce controllable channels and verify the performance of the developed channel sounder. Finally, the developed channel sounder is applied to carry out A2G measurement campaigns at 3.5 GHz in a campus scenario. The channel characteristics, that is, path loss (PL), K -factor, and path angle are analyzed. The measured channel characteristics are consistent with existing measurements under a similar scenario. The estimated path angles are also validated by the theoretical results. Thus, the channel sounder can be used to capture the nonstationary A2G channel characteristics for the system design and algorithm optimization of A2G communications.</p
Shapes, contact angles, and line tensions of droplets on cylinders
Using an interface displacement model we calculate the shapes of
nanometer-size liquid droplets on homogeneous cylindrical surfaces. We
determine effective contact angles and line tensions, the latter defined as
excess free energies per unit length associated with the two contact lines at
the ends of the droplet. The dependences of these quantities on the cylinder
radius and on the volume of the droplets are analyzed.Comment: 26 pages, RevTeX, 10 Figure
Experimental study for local air/water flow structure of bubbly and slug flow regime
Paper presented at the 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Malta, 16-18 July, 2012.A study for local hydraulic characteristics of water and air/steam mixture flow is a very challenging topic for advanced thermal hydraulic analysis code development. Recently, many researchers made efforts in the study of mechanistic feature related to the two phase dynamics such as an interfacial area transport model. The mechanistic study for the interfacial area needs a lot of understanding for the bubble/drop dynamics and flow propagation phenomena. To generate an experimental data base for a modeling, an air/water test was performed in this study. The facility has a cylindrical acryl test section of which the diameter and height are 80 mm and 10m, respectively. The major local parameters to be measured are the void fraction, bubble/liquid velocities, interfacial area concentration and bubble size. To investigate the transport phenomena of the twophase parameters, a local probe and an impedance void meter(IVM) are installed at three axial elevations of the test section. (L/D=12.2, 42.2, 100.7) The test range covers 0.5~2.8 m/s and 0.04~1.2 m/s of the superficial liquid and gas velocity, respectively, which corresponds to the bubbly and slug flow regimes. The system pressure conditions are 0.2~0.3 MPa at the L/D=12.2.dc201
Importin α5 regulates anxiety through MeCP2 and sphingosine kinase 1
Importins mediate transport from synapse to soma and from cytoplasm to nucleus, suggesting that perturbation of importin-dependent pathways should have significant neuronal consequences. A behavioral screen on five importin α knockout lines revealed that reduced expression of importin α5 (KPNA1) in hippocampal neurons specifically decreases anxiety in mice. Re-expression of importin α5 in ventral hippocampus of knockout animals increased anxiety behaviors to wild-type levels. Hippocampal neurons lacking importin α5 reveal changes in presynaptic plasticity and modified expression of MeCP2-regulated genes, including sphingosine kinase 1 (Sphk1). Knockout of importin α5, but not importin α3 or α4, reduces MeCP2 nuclear localization in hippocampal neurons. A Sphk1 blocker reverses anxiolysis in the importin α5 knockout mouse, while pharmacological activation of sphingosine signaling has robust anxiolytic effects in wild-type animals. Thus, importin α5 influences sphingosine-sensitive anxiety pathways by regulating MeCP2 nuclear import in hippocampal neurons
Magnetic Flux of EUV Arcade and Dimming Regions as a Relevant Parameter for Early Diagnostics of Solar Eruptions - Sources of Non-Recurrent Geomagnetic Storms and Forbush Decreases
This study aims at the early diagnostics of geoeffectiveness of coronal mass
ejections (CMEs) from quantitative parameters of the accompanying EUV dimming
and arcade events. We study events of the 23th solar cycle, in which major
non-recurrent geomagnetic storms (GMS) with Dst <-100 nT are sufficiently
reliably identified with their solar sources in the central part of the disk.
Using the SOHO/EIT 195 A images and MDI magnetograms, we select significant
dimming and arcade areas and calculate summarized unsigned magnetic fluxes in
these regions at the photospheric level. The high relevance of this eruption
parameter is displayed by its pronounced correlation with the Forbush decrease
(FD) magnitude, which, unlike GMSs, does not depend on the sign of the Bz
component but is determined by global characteristics of ICMEs. Correlations
with the same magnetic flux in the solar source region are found for the GMS
intensity (at the first step, without taking into account factors determining
the Bz component near the Earth), as well as for the temporal intervals between
the solar eruptions and the GMS onset and peak times. The larger the magnetic
flux, the stronger the FD and GMS intensities are and the shorter the ICME
transit time is. The revealed correlations indicate that the main quantitative
characteristics of major non-recurrent space weather disturbances are largely
determined by measurable parameters of solar eruptions, in particular, by the
magnetic flux in dimming areas and arcades, and can be tentatively estimated in
advance with a lead time from 1 to 4 days. For GMS intensity, the revealed
dependencies allow one to estimate a possible value, which can be expected if
the Bz component is negative.Comment: 27 pages, 5 figures. Accepted for publication in Solar Physic
On the study of oil paint adhesion on optically transparent glass: Conservation of reverse paintings on glass
Archived with thanks to Applied Surface Science, ElsevierReverse painting on glass is a technique which consists of applying a cold paint layer on the reverse-side of glass. The main challenge facing these artworks is the fragile adhesion of the pictorial layer – a simple movement can modify the appearance of the painting. This paper details a study into the adhesion parameters of pigments on glass and the comparison between different pigments. The relationships between the binder (linseed oil) with pigments and the glass with or without the use of an adhesive are studied. Physical analyses by surface characterisation have been carried out to better understand the influence of the pigment. The use of a sessile drop device, optical microscopy, scanning electron microscopy (SEM), a surface 3D profiler and a pencil hardness scratch tester were necessary to establish a comparison of the pictorial layer adhesion. A comparison of the effect of two adhesives; namely ox gall and gum arabic, has shown that the adhesion is not only linked to the physical parameters but that possible chemical reactions can influence the results. Finally, a treatment based on humidity-extreme storage has shown the weakness of some pictorial layers
Effect of Quantum Fluctuations in an Ising System on Small-World Networks
We study quantum Ising spins placed on small-world networks. A simple model
is considered in which the coupling between any given pair of spins is a
nonzero constant if they are linked in the small-world network and zero
otherwise. By applying a transverse magnetic field, we have investigated the
effect of quantum fluctuations. Our numerical analysis shows that the quantum
fluctuations do not alter the universality class at the ferromagnetic phase
transition, which is of the mean-field type. The transition temperature is
reduced by the quantum fluctuations and eventually vanishes at the critical
transverse field . With increasing rewiring probability,
is shown to be enhanced.Comment: 5 pages, 5 figure
Two-species percolation and Scaling theory of the metal-insulator transition in two dimensions
Recently, a simple non-interacting-electron model, combining local quantum
tunneling via quantum point contacts and global classical percolation, has been
introduced in order to describe the observed ``metal-insulator transition'' in
two dimensions [1]. Here, based upon that model, a two-species-percolation
scaling theory is introduced and compared to the experimental data. The two
species in this model are, on one hand, the ``metallic'' point contacts, whose
critical energy lies below the Fermi energy, and on the other hand, the
insulating quantum point contacts. It is shown that many features of the
experiments, such as the exponential dependence of the resistance on
temperature on the metallic side, the linear dependence of the exponent on
density, the scale of the critical resistance, the quenching of the
metallic phase by a parallel magnetic field and the non-monotonic dependence of
the critical density on a perpendicular magnetic field, can be naturally
explained by the model.
Moreover, details such as the nonmonotonic dependence of the resistance on
temperature or the inflection point of the resistance vs. parallel magnetic are
also a natural consequence of the theory. The calculated parallel field
dependence of the critical density agrees excellently with experiments, and is
used to deduce an experimental value of the confining energy in the vertical
direction. It is also shown that the resistance on the ``metallic'' side can
decrease with decreasing temperature by an arbitrary factor in the degenerate
regime ().Comment: 8 pages, 8 figure
Physiological and psychological effects of olfactory stimulation with D-limonene
Although D-Limonene can be considered an important component of nature-based stimuli, the physiological effects of olfactory stimulation with D-Limonene have not been completely clarified by scientific studies. The physiological and psychological effects of olfactory stimulation with D-Limonene were studied measuring heart rate variability (HRV), heart rate, and subjective evaluation using a modified semantic differential method; thirteen Japanese female university students (mean age±SD, 21.5±1.0 years) participated in the study. A concentration of 60 μL of D-Limonene was used as olfactory stimulant and room air as control. Subjects were exposed for 90 s while sitting with eyes closed. During D-Limonene inhalation: (1) the high-frequency (HF) value of HRV, a marker of parasympathetic nervous activity that is enhanced in relaxing situations, was significantly higher; (2) the heart rate was significantly lower; and (3) subjects reported feeling significantly more comfortable during D-Limonene administration than control. The results obtained clearly indicate that olfactory stimulation with D-Limonene induced physiological and psychological relaxation, providing important scientific evidence of the health benefits of D-Limonene
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