10,048 research outputs found
Fish Lateral Line Neurophysiological and Neurobehavioral Responses as a Sensitive Water Quality Monitoring System
Cadmium is a heavy metal ion that can cause deleterious effects on aquatic animals. This study uses both electrophysiological recordings from lateral line nerves and videotaping of schooling behavior to investigate the effects of cadmium exposure on fish. The fathead minnows were exposed to cadmium at a concentration of 450 μg/1 over a 24-hr period. Extracellular recording with a silver hook electrode was used to record compound action potentials from the lateral lines of control and experimental fish. After a short time exposure (24 hr) to cadmium ions, all of the electrophysiological activities of the lateral line nerves were suppressed. However, after a 10-day recovery in clean water, the function of the lateral line nerves was regained. Schooling behavior observed under lighted conditions showed no significant difference (in terms of percentage of time forming a school) between control and experimental fish. Schooling behavior, however, was completely lost for experimental fish when observed under complete darkness but it was regained after a 10-day recovery in clean water. The current study shows that both electrophysiological recording from the lateral line nerve and observation of schooling behavior can be used as effective assay methods for cadmium toxicity studies
Exact solution of gyration radius of individual's trajectory for a simplified human mobility model
Gyration radius of individual's trajectory plays a key role in quantifying
human mobility patterns. Of particular interests, empirical analyses suggest
that the growth of gyration radius is slow versus time except the very early
stage and may eventually arrive to a steady value. However, up to now, the
underlying mechanism leading to such a possibly steady value has not been well
understood. In this Letter, we propose a simplified human mobility model to
simulate individual's daily travel with three sequential activities: commuting
to workplace, going to do leisure activities and returning home. With the
assumption that individual has constant travel speed and inferior limit of time
at home and work, we prove that the daily moving area of an individual is an
ellipse, and finally get an exact solution of the gyration radius. The
analytical solution well captures the empirical observation reported in [M. C.
Gonz`alez et al., Nature, 453 (2008) 779]. We also find that, in spite of the
heterogeneous displacement distribution in the population level, individuals in
our model have characteristic displacements, indicating a completely different
mechanism to the one proposed by Song et al. [Nat. Phys. 6 (2010) 818].Comment: 4 pages, 4 figure
Steady Bell state generation via magnon-photon coupling
We show that parity-time () symmetry can be spontaneously
broken in the recently reported energy level attraction of magnons and cavity
photons. In the -broken phase, magnon and photon form a
high-fidelity Bell state with maximum entanglement. This entanglement is steady
and robust against the perturbation of environment, in contrast to the general
wisdom that expects instability of the hybridized state when the symmetry is
broken. This anomaly is further understood by the compete of non-Hermitian
evolution and particle number conservation of the hybridized system. As a
comparison, neither -symmetry broken nor steady magnon-photon
entanglement is observed inside the normal level repulsion case. Our results
may open a novel window to utilize magnon-photon entanglement as a resource for
quantum technologies.Comment: 5 pages, 4 figure
Measurement of ultralow injection current to polymethyl-methacrylate film
2007-2008 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe
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An experimental study of dynamic flow of nanofluid with different concentrations
This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.Current reported data of nanofluid concentration is almost all based on TEM observation, which is in a static situation. No data of dynamic concentration during flow is reported. In the present study, an experimental measurement based on nuclear magnetic resonance (NMR) of monitoring the dynamic concentrations of nanofluid flow is carried out. It is demonstrated that the ferrofluid with Fe3O4 as its nanoparticles coated with surfactant as a special type of nanofluid can be used as T2 contrast agent in NMR scanning as well as a magnetic and thermal sensitive nanoparticle solution that would enhance heat transfer
Effects of relative orientation of the molecules on electron transport in molecular devices
Effects of relative orientation of the molecules on electron transport in
molecular devices are studied by non-equilibrium Green's function method based
on density functional theory. In particular, two molecular devices, with the
planer Au and Ag clusters sandwiched between the Al(100) electrodes
are studied. In each device, two typical configurations with the clusters
parallel and vertical to the electrodes are considered. It is found that the
relative orientation affects the transport properties of these two devices
completely differently. In the Al(100)-Au-Al(100) device, the conductance
and the current of the parallel configuration are much larger than those in the
vertical configuration, while in the Al(100)-Ag-Al(100) device, an
opposite conclusion is obtained
Reconsideration of Second Harmonic Generation from neat Air/Water Interface: Broken of Kleinman Symmetry from Dipolar Contribution
It has been generally accepted that there are significant quadrupolar and
bulk contributions to the second harmonic generation (SHG) reflected from the
neat air/water interface, as well as common liquid interfaces. Because there
has been no general methodology to determine the quadrupolar and bulk
contributions to the SHG signal from a liquid interface, this conclusion was
reached based on the following two experimental phenomena. Namely, the broken
of the macroscopic Kleinman symmetry, and the significant temperature
dependence of the SHG signal from the neat air/water interface. However,
because sum frequency generation vibrational spectroscopy (SFG-VS) measurement
of the neat air/water interface observed no apparent temperature dependence,
the temperature dependence in the SHG measurement has been reexamined and
proven to be an experimental artifact. Here we present a complete microscopic
analysis of the susceptibility tensors of the air/water interface, and show
that dipolar contribution alone can be used to address the issue of broken of
the macroscopic Kleinman symmetry at the neat air/water interface. Using this
analysis, the orientation of the water molecules at the interface can be
obtained, and it is consistent with the measurement from SFG-VS. Therefore, the
key rationales to conclude significantly quadrupolar and bulk contributions to
the SHG signal of the neat air/water interface can no longer be considered as
valid as before. This new understanding of the air/water interface can shed
light on our understanding of the nonlinear optical responses from other
molecular interfaces as well
Dopant Profile Extraction by Inverse Modeling of Scanning Capacitance Microscopy Using Peak dC/dV
Scanning capacitance microscopy (SCM) has proven to be successful for junction delineation. However quantitative dopant profile extraction by SCM still remains a difficult challenge, due to limited understanding of relevant physics especially at p-n junction, as well as difficulties to accurately quantify all parameters in modeling. In this paper we present a new procedure, the use of peak dC/dV at every spatial point, for dopant profile extraction. The advantage of such a technique is twofold. First it eliminates problems encountered using a fixed dc bias such as contrast reversal. Second, it also excludes the need to model interface traps. This is because the peak dC/dV value is independent of the presence of interface traps, as demonstrated in our experimental results. Furthermore, based on our understanding of the influence of mobility degradation at p-n junction, we propose that low surface mobility model should be used in simulation so that only the accumulation-to-depletion dC/dV is extracted
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