15,554 research outputs found
Dynamical photo-induced electronic properties of molecular junctions
Nanoscale molecular-electronic devices and machines are emerging as promising
functional elements, naturally flexible and efficient, for next generation
technologies. A deeper understanding of carrier dynamics in molecular junctions
is expected to benefit many fields of nanoelectronics and power-devices. We
determine time-resolved charge current flowing at donor- acceptor interface in
molecular junctions connected to metallic electrodes by means of quantum
transport simulations. The current is induced by the interaction of the donor
with a Gaussian-shape femtosecond laser pulse. Effects of the molecular
internal coupling, metal- molecule tunneling and light-donor coupling on
photocurrent are discussed. We then examine the junction working through the
time-resolved donor density of states. Non-equilibrium reorganization of
hybridized molecular orbitals through the light-donor interaction gives rise to
two phenomena: the dynamical Rabi shift and the appearance of Floquet-like
states. Such insights into the dynamical photoelectronic structure of molecules
are of strong interest for ultrafast spectroscopy, and open avenues toward the
possibility of analyzing and controlling the internal properties of quantum
nanodevices with pump-push photocurrent spectroscopy
A Transition State Theory for Calculating Hopping Times and Diffusion in Highly Confined Fluids
Monte Carlo simulation is used to study the dynamical crossover from single
file diffusion to normal diffusion in fluids confined to narrow channels. We
show that the long time diffusion coefficients for a series of systems
involving hard and soft interaction potentials can be described in terms of a
hopping time that measures the time it takes for a particle to escape the cage
formed by its neighbors in the pore. Free energy barriers for the particle
hopping process are calculated and used to show that transition state theory
effectively describes the hopping time for all the systems studied, over a
range of pore diameters. Our work suggests that the combination of hopping
times and transition state theory offers a useful and general framework to
describe the dynamics of these highly confined fluids.Comment: 6 figure
Fear from the heart: sensitivity to fear stimuli depends on individual heartbeats
Cognitions and emotions can be influenced by bodily physiology. Here, we investigated whether the processing of brief fear stimuli is selectively gated by their timing in relation to individual heartbeats. Emotional and neutral faces were presented to human volunteers at cardiac systole, when ejection of blood from the heart causes arterial baroreceptors to signal centrally the strength and timing of each heartbeat, and at diastole, the period between heartbeats when baroreceptors are quiescent. Participants performed behavioral and neuroimaging tasks to determine whether these interoceptive signals influence the detection of emotional stimuli at the threshold of conscious awareness and alter judgments of emotionality of fearful and neutral faces. Our results show that fearful faces were detected more easily and were rated as more intense at systole than at diastole. Correspondingly, amygdala responses were greater to fearful faces presented at systole relative to diastole. These novel findings highlight a major channel by which short-term interoceptive fluctuations enhance perceptual and evaluative processes specifically related to the processing of fear and threat and counter the view that baroreceptor afferent signaling is always inhibitory to sensory perception
Recommended from our members
BVPSMS: A Batch Verification Protocol for End-to-End Secure SMS for Mobile Users
Short Message Service (SMS) is a widely used communication medium for mobile applications, such as banking, social networking, and e-commerce. Applications of SMS services also include real-time broadcasting messages, such as notification of natural disasters and terrorist attacks, and sharing the current whereabouts to other users, such as notifying urgent business meeting information, transmitting quick information in the battlefield to multiple users, notifying current location to our friends, and sharing market information. However, traditional SMS is not designed with security in mind (e.g. messages are not securely sent). In this paper, we introduce a batch verification Authentication and Key Agreement (AKA) protocol, BVPSMS, which provides end-to-end message security over an insecure communication channel between different Mobile Subscribers (MSs). Specifically, the proposed protocol securely transmits SMS from one MS to multiple MS simultaneously. We then evaluate the performance of the BVPSMS protocol in terms of communication and computation overheads, protocol execution time, and batch and re-batch verification times. The impacts of the user mobility, and the time, space, and cost complexity analysis are also discussed. We present a formal proof of the proposed protocol. To the best of our knowledge, this is the first provably-secure batch verification AKA protocol, which provides end-to-end security to the SMS using symmetric keys
Time--Splitting Schemes and Measure Source Terms for a Quasilinear Relaxing System
Several singular limits are investigated in the context of a
system arising for instance in the modeling of chromatographic processes. In
particular, we focus on the case where the relaxation term and a
projection operator are concentrated on a discrete lattice by means of Dirac
measures. This formulation allows to study more easily some time-splitting
numerical schemes
High Spatial Resolution Observations of Two Young Protostars in the R Corona Australis Region
We present multi-wavelength, high spatial resolution imaging of the IRS 7
region in the R Corona Australis molecular cloud. Our observations include 1.1
mm continuum and HCO^+ J = images from the SMA, ^{12}CO J =
outflow maps from the DesertStar heterodyne array receiver on the HHT, 450
m and 850 m continuum images from SCUBA, and archival Spitzer IRAC
and MIPS 24 \micron images. The accurate astrometry of the IRAC images allow us
to identify IRS 7 with the cm source VLA 10W (IRS 7A) and the X-ray source X_W.
The SMA 1.1 mm image reveals two compact continuum sources which are also
distinguishable at 450 m. SMA 1 coincides with X-ray source CXOU
J190156.4-365728 and VLA cm source 10E (IRS 7B) and is seen in the IRAC and
MIPS images. SMA 2 has no infrared counterpart but coincides with cm source VLA
9. Spectral energy distributions constructed from SMA, SCUBA and Spitzer data
yield bolometric temperatures of 83 K for SMA 1 and 70 K for SMA 2. These
temperatures along with the submillimeter to total luminosity ratios indicate
that SMA 2 is a Class 0 protostar, while SMA 1 is a Class 0/Class I
transitional object (L= \Lsun). The ^{12}CO J = outflow map
shows one major and possibly several smaller outflows centered on the IRS 7
region, with masses and energetics consistent with previous work. We identify
the Class 0 source SMA 2/VLA 9 as the main driver of this outflow. The complex
and clumpy spatial and velocity distribution of the HCO^+ J =
emission is not consistent with either bulk rotation, or any known molecular
outflow activity.Comment: 31 pages, 8 figures, Accepted to Ap
Perbandingan Metode KNN, Naive Bayes, dan Regresi Logistik Binomial dalam Pengklasifikasian Status Ekonomi Negara
The classification of a country's economic status as developed or developing often involves factors such as life expectancy and its underlying variables. This research aims to compare the performance of three machine learning algorithms, namely KNN (K-Nearest Neighbors), naive Bayes, and binomial logistic regression, in classifying the economic status of countries as developed or developing. The data used in this study is "Life Expectancy (WHO) Fixed," obtained from the Kaggle website. The first statistical analysis conducted was Principal Component Analysis (PCA) using 16 predictor variables. PCA resulted in three principal components capable of explaining 71.41% of the variance, which were subsequently used in the KNN, naive Bayes, and binomial logistic regression methods. The analysis results from the KNN, naive Bayes, and binomial logistic regression methods produced F1-scores of 100\%, 98.19%, and 97.36%, respectively
Habitable Planet Formation in Binary-Planetary Systems
Recent radial velocity observations have indicated that Jovian-type planets
can exist in moderately close binary star systems. Numerical simulations of the
dynamical stability of terrestrial-class planets in such environments have
shown that, in addition to their giant planets, these systems can also harbor
Earth-like objects. In this paper, we study the late stage of terrestrial
planet formation in such binary-planetary systems, and present the results of
the simulations of the formation of Earth-like bodies in their habitable zones.
We consider a circumprimary disk of Moon- to Mars-sized objects and numerically
integrate the orbits of these bodies at the presence of the Jovian-type planet
of the system and for different values of the mass, semimajor axis, and orbital
eccentricity of the secondary star. Results indicate that, Earth-like objects,
with substantial amounts of water, can form in the habitable zone of the
primary star. Simulations also indicate that, by transferring angular momentum
from the secondary star to protoplanetary objects, the giant planet of the
system plays a key role in the radial mixing of these bodies and the water
contents of the final terrestrial planets. We will discuss the results of our
simulation and show that the formation of habitable planets in binary-planetary
systems is more probable in binaries with moderate to large perihelia.Comment: 27 pages, 11 figures, submitted for publicatio
- …