1,225 research outputs found
Structural basis for oligomerization and glycosaminoglycan binding of CCL5 and CCL3.
CC chemokine ligand 5 (CCL5) and CCL3 are critical for immune surveillance and inflammation. Consequently, they are linked to the pathogenesis of many inflammatory conditions and are therapeutic targets. Oligomerization and glycosaminoglycan (GAG) binding of CCL5 and CCL3 are vital for the functions of these chemokines. Our structural and biophysical analyses of human CCL5 reveal that CCL5 oligomerization is a polymerization process in which CCL5 forms rod-shaped, double-helical oligomers. This CCL5 structure explains mutational data and offers a unified mechanism for CCL3, CCL4, and CCL5 assembly into high-molecular-weight, polydisperse oligomers. A conserved, positively charged BBXB motif is key for the binding of CC chemokines to GAG. However, this motif is partially buried when CCL3, CCL4, and CCL5 are oligomerized; thus, the mechanism by which GAG binds these chemokine oligomers has been elusive. Our structures of GAG-bound CCL5 and CCL3 oligomers reveal that these chemokine oligomers have distinct GAG-binding mechanisms. The CCL5 oligomer uses another positively charged and fully exposed motif, KKWVR, in GAG binding. However, residues from two partially buried BBXB motifs along with other residues combine to form a GAG-binding groove in the CCL3 oligomer. The N termini of CC chemokines are shown to be involved in receptor binding and oligomerization. We also report an alternative CCL3 oligomer structure that reveals how conformational changes in CCL3 N termini profoundly alter its surface properties and dimer-dimer interactions to affect GAG binding and oligomerization. Such complexity in oligomerization and GAG binding enables intricate, physiologically relevant regulation of CC chemokine functions
Single channel wireless EEG device for real-time fatigue level detection
© 2015 IEEE. Driver fatigue problem is one of the important factors of traffic accidents. Recent years, many research had investigated that using EEG signals can effectively detect driver's drowsiness level. However, real-time monitoring system is required to apply these fatigue level detection techniques in the practical application, especially in the real-road driving. Therefore, it required less channels, portable and wireless, real-time monitoring and processing techniques for developing the real-time monitoring system. In this study, we develop a single channel wireless EEG device which can real-time detect driver's fatigue level on the mobile device such as smart phone or tablet. The developed device is investigated to obtain a better and precise understanding of brain activities of mental fatigue under driving, which is of great benefit for devolvement of detection of driving fatigue system. This system consists of a Bluetooth-enabled one channel EEG, a regression model, and smartphone, which was a platform recording and transforming the raw EEG data to useful driving status. In the experiment, this was a sustained-attention driving task to implement in a virtual-reality (VR) driving simulator. To training model and develop the system, we were performed for 15 subjects to study Electroencephalography (EEG) brain dynamics by using a mobile and wireless EEG device. Based on the outstanding training results, the leave-one-subject-out cross validation test obtained 90% fatigue detection accuracy. These results indicate that the combination of a smartphone and wireless EEG device constitutes an effective and easy wearable solution for detecting and preventing driver fatigue in real driving environments
Nonequilibrium Singlet-Triplet Kondo Effect in Carbon Nanotubes
The Kondo-effect is a many-body phenomenon arising due to conduction
electrons scattering off a localized spin. Coherent spin-flip scattering off
such a quantum impurity correlates the conduction electrons and at low
temperature this leads to a zero-bias conductance anomaly. This has become a
common signature in bias-spectroscopy of single-electron transistors, observed
in GaAs quantum dots as well as in various single-molecule transistors. While
the zero-bias Kondo effect is well established it remains uncertain to what
extent Kondo correlations persist in non-equilibrium situations where inelastic
processes induce decoherence. Here we report on a pronounced conductance peak
observed at finite bias-voltage in a carbon nanotube quantum dot in the spin
singlet ground state. We explain this finite-bias conductance anomaly by a
nonequilibrium Kondo-effect involving excitations into a spin triplet state.
Excellent agreement between calculated and measured nonlinear conductance is
obtained, thus strongly supporting the correlated nature of this nonequilibrium
resonance.Comment: 21 pages, 5 figure
Spectroscopic analysis of finite size effects around a Kondo quantum dot
We consider a simple setup in which a small quantum dot is strongly connected
to a finite size box. This box can be either a metallic box or a finite size
quantum wire.The formation of the Kondo screening cloud in the box strongly
depends on the ratio between the Kondo temperature and the box level spacing.
By weakly connecting two metallic reservoirs to the quantum dot, a detailed
spectroscopic analysis can be performed. Since the transport channels and the
screening channels are almost decoupled, such a setup allows an easier access
to the measure of finite-size effects associated with the finite extension of
the Kondo cloud.Comment: contribution to Les Houches proceeding, ``Quantum magnetism'' 200
The Kondo effect in ferromagnetic atomic contacts
Iron, cobalt and nickel are archetypal ferromagnetic metals. In bulk,
electronic conduction in these materials takes place mainly through the and
electrons, whereas the magnetic moments are mostly in the narrow
-electron bands, where they tend to align. This general picture may change
at the nanoscale because electrons at the surfaces of materials experience
interactions that differ from those in the bulk. Here we show direct evidence
for such changes: electronic transport in atomic-scale contacts of pure
ferromagnets (iron, cobalt and nickel), despite their strong bulk
ferromagnetism, unexpectedly reveal Kondo physics, that is, the screening of
local magnetic moments by the conduction electrons below a characteristic
temperature. The Kondo effect creates a sharp resonance at the Fermi energy,
affecting the electrical properties of the system;this appears as a Fano-Kondo
resonance in the conductance characteristics as observed in other artificial
nanostructures. The study of hundreds of contacts shows material-dependent
lognormal distributions of the resonance width that arise naturally from Kondo
theory. These resonances broaden and disappear with increasing temperature,
also as in standard Kondo systems. Our observations, supported by calculations,
imply that coordination changes can significantly modify magnetism at the
nanoscale. Therefore, in addition to standard micromagnetic physics, strong
electronic correlations along with atomic-scale geometry need to be considered
when investigating the magnetic properties of magnetic nanostructures.Comment: 7 pages, 5 figure
Improving corporate governance in state-owned corporations in China: which way forward?
This article discusses corporate governance in China. It outlines the basic agency problem in Chinese listed companies and questions the effectiveness of the current mechanisms employed to improve their standards of governance. Importantly, it considers alternative means through which corporate practice in China can be brought into line with international expectations and stresses the urgency with which this task must be tackled. It concludes that regulators in China must construct a corporate governance model which is compatible with its domestic setting and not rush to adopt governance initiatives modelled on those in cultures which are fundamentally different in the hope of also reproducing their success
Search for K_S K_L in psi'' decays
K_S K_L from psi'' decays is searched for using the psi'' data collected by
BESII at BEPC, the upper limit of the branching fraction is determined to be
B(psi''--> K_S K_L) < 2.1\times 10^{-4} at 90% C. L. The measurement is
compared with the prediction of the S- and D-wave mixing model of the
charmonia, based on the measurements of the branching fractions of J/psi-->K_S
K_L and psi'-->K_S K_L.Comment: 5 pages, 1 figur
Airflow Dynamics of Coughing in Healthy Human Volunteers by Shadowgraph Imaging: An Aid to Aerosol Infection Control
Cough airflow dynamics have been previously studied using a variety of experimental methods. In this study, real-time, non-invasive shadowgraph imaging was applied to obtain additional analyses of cough airflows produced by healthy volunteers. Twenty healthy volunteers (10 women, mean age 32.2±12.9 years; 10 men, mean age 25.3±2.5 years) were asked to cough freely, then into their sleeves (as per current US CDC recommendations) in this study to analyze cough airflow dynamics. For the 10 females (cases 1–10), their maximum detectable cough propagation distances ranged from 0.16–0.55 m, with maximum derived velocities of 2.2–5.0 m/s, and their maximum detectable 2-D projected areas ranged from 0.010–0.11 m2, with maximum derived expansion rates of 0.15–0.55 m2/s. For the 10 males (cases 11–20), their maximum detectable cough propagation distances ranged from 0.31–0.64 m, with maximum derived velocities of 3.2–14 m/s, and their maximum detectable 2-D projected areas ranged from 0.04–0.14 m2, with maximum derived expansion rates of 0.25–1.4 m2/s
Development of an IS change reason - IS change type combination matrix
Firms change their information systems (IS) for various reasons, ranging from compliance with government regulations to the development of new capabilities. When making these changes a firm can choose between four different IS change types: IS introduction, IS extension, IS replacement, and IS merger. This paper proposes that change reasons and change types are interrelated, and that certain reason-type combinations are more likely than others to result in a successful IS change. To identify these combinations, an IS change reason–IS change type matrix is developed. While the matrix is created from prior IS research, we conducted a focus group study of IS professionals to further explore and refine the matrix. The findings from the focus group study reveal that some IS change reason–IS change type combinations are more appropriate than others to carry out the IS change project successfully. We also present three examples of IS change projects to illustrate the use and value of the matrix in practice
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