4,776 research outputs found
Internal magnetic field effect on magnetoelectricity in orthorhombic crystals
We have investigated the role of the 4 moment on the magnetoelectric (ME)
effect of orthorhombic MnO (=rare earth ions). In order to clarify
the role of the 4 moment, we prepared three samples: (Eu,Y)MnO without
the 4 moment, TbMnO with the anisotropic 4 moment, and
(Gd,Y)MnO with the isotropic 4 moment. The ferroelectric behaviors of
these samples are different from each other in a zero magnetic field.
(Eu,Y)MnO and (Gd,Y)MnO show the ferroelectric polarization along
the a axis in the ground state, while TbMnO shows it along the c axis.
Such difference may arise from the influence of the anisotropic Tb 4
moment. The direction of the ferroelectric polarization of MnO is
determined by the internal magnetic field arising from the 4 moment.Comment: 2 pages, 1 figure, the proceeding of International Conference of
Magnetism, to be published in the Journal of Magnetism and Magnetic Material
Improved detection of nitric oxide radical (NO•) production in an activated macrophage culture with a radical scavenger, car☐y PTIO, and Griess reagent
AbstractAn improved method for the detection of nitric oxide radicals (NO•in cultures of activated macrophages was developed, involving a nitric oxide radical scavenger, 2-(4-car☐yphenyl)-4, 4, 5, 5-tetramethylimidazoline-3-oxide-l-oxyl (car☐y PTIO) and Griess reagent. A murine macrophage-like cell line, J774.1, was activated with interferon-γ (IFN-γ) and bacterial lipopolysaccharide (LPS), which induced the production and secretion of NO2− into the culture supernatant. Addition of car☐y PTIO to the activated macrophages increased the amount of NO2−1 to 4- to 5-fold without cell damages, probably because car☐y PTIO rapidly reacted with NO• to form NO2−1 which was finally assayed by the Griess reaction
Understanding Link Dynamics in Wireless Sensor Networks with Dynamically Steerable Directional Antennas
Abstract. By radiating the power in the direction of choice, electronicallyswitched directional (ESD) antennas can reduce network contention and avoid packet loss. There exists some ESD antennas for wireless sensor networks, but so far researchers have mainly evaluated their directionality. There are no studies regarding the link dynamics of ESD antennas, in particular not for indoor deployments and other scenarios where nodes are not necessarily in line of sight. Our long-term experiments confirm that previous findings that have demonstrated the dependence of angleof-arrival on channel frequency also hold for directional transmissions with ESD antennas. This is important for the design of protocols for wireless sensor networks with ESD antennas: the best antenna direction, i.e., the direction that leads to the highest packet reception rate and signal strength at the receiver, is not stable but varies over time and with the selected IEEE 802.15.4 channel. As this requires protocols to incorporate some form of adaptation, we present an intentionally simple and yet efficient mechanism for selecting the best antenna direction at run-time with an energy overhead below 2 % compared to standard omni-directional transmissions.
Theory of magnetic field-induced metaelectric critical end point in BiMnO
A recent experiment on the multiferroic BiMnO compound under a strong
applied magnetic field revealed a rich phase diagram driven by the coupling of
magnetic and charge (dipolar) degrees of freedom. Based on the
exchange-striction mechanism, we propose here a theoretical model with the
intent to capture the interplay of the spin and dipolar moments in the presence
of a magnetic field in BiMnO. Experimentally observed behavior of the
dielectric constants, magnetic susceptibility, and the polarization is, for the
most part, reproduced by our model. The critical behavior observed near the
polarization reversal point in the phase diagram is interpreted as
arising from the proximity to the critical end point.Comment: Theory; relevant experiment uploaded as arXiv:0810.190
Infrared Emission from the Radio Supernebula in NGC 5253: A Proto-Globular Cluster?
Hidden from optical view in the starburst region of the dwarf galaxy NGC 5253
lies an intense radio source with an unusual spectrum which could be
interpreted variously as nebular gas ionized by a young stellar cluster or
nonthermal emission from a radio supernova or an AGN. We have obtained 11.7 and
18.7 micron images of this region at the Keck Telescope and find that it is an
extremely strong mid-infrared emitter. The infrared to radio flux ratio rules
out a supernova and is consistent with an HII region excited by a dense cluster
of young stars. This "super nebula" provides at least 15% of the total
bolometric luminosity of the galaxy. Its excitation requires 10^5-10^6 stars,
giving it the total mass and size (1-2 pc diameter) of a globular cluster.
However, its high obscuration, small size, and high gas density all argue that
it is very young, no more than a few hundred thousand years old. This may be
the youngest globular cluster yet observed.Comment: 6 pages, 2 color figures, Submitted to the ApJL, Revised 4/6/01 based
on referee's comment
Counting RNAseq reads: which way is better?
In this work we show the variation of results we?ve found while working with ~1 billion Illumina reads from drought tolerant Sorghum bicolor genotype in the presence and absence of the stress and compared results found for key genes already characterized.Pôster N101
Photonic stop bands in quasi-random nanoporous anodic alumina structures
The existence of photonic stop bands in the self-assembled arrangement of
pores in porous anodic alumina structures is investigated by means of rigorous
2D finite- difference time-domain calculations. Self-assembled porous anodic
alumina shows a random distribution of domains, each of them with a very
definite triangular pattern, constituting a quasi-random structure. The
observed stop bands are similar to those of photonic quasicrystals or random
structures. As the pores of nanoporous anodic alumina can be infiltrated with
noble metals, nonlinear or active media, it makes this material very attractive
and cost-effective for applications including inhibition of spontaneous
emission, random lasing, LEDs and biosensors
Reactive Hall response
The zero temperature Hall constant R_H, described by reactive
(nondissipative) conductivities, is analyzed within linear response theory. It
is found that in a certain limit, R_H is directly related to the density
dependence of the Drude weight implying a simple picture for the change of sign
of charge carriers in the vicinity of a Mott-Hubbard transition. This novel
formulation is applied to the calculation of R_H in quasi-one dimensional and
ladder prototype interacting electron systems.Comment: 4 pages, 3 Postscript figure
- …