419 research outputs found
Substrate Atomic-Termination-Induced Anisotropic Growth of ZnO Nanowires/Nanorods by the VLS Process
Unconventional superconductivity of NdFeAsO0.82F0.18 indicated by the low temperature dependence of the lower critical field Hc1
We measured the initial M-H curves for a sample of the newly discovered
superconductor NdFeAsO0.82Fe0.18, which had a critical temperature, Tc, of 51
K, and was fabricated at the high pressure of 6 GPa. The lower critical field,
Hc1, was extracted from the deviation point of the Meissner linearity in the
M-H curves, which show linear temperature dependence in the low temperature
region down to 5 K. The Hc1(T) indicates no s-wave superconductivity, but
rather an unconventional superconductivity with a nodal gap structure.
Furthermore, the linearity of Hc1 at low temperature does not hold at high
temperature, but shows other characteristics, indicating that this
superconductor might have multi-gap features. Based on the low temperature
nodal gap structure, we estimate that the maximum gap magnitude delta 0 =
(1.6+- 0.2) kBTc.Comment: 8 pages, 3 figure
First Census of Gas-phase Metallicity Gradients of Star-forming Galaxies in Overdense Environments at Cosmic Noon
We report the first spatially resolved measurements of gas-phase metallicity
radial gradients in star-forming galaxies in overdense environments at
. The spectroscopic data are acquired by the \mg\ survey, a Hubble
Space Telescope (HST) cycle-28 medium program. This program is obtaining 45
orbits of WFC3/IR grism spectroscopy in the density peak regions of three
massive galaxy protoclusters (BOSS 1244, BOSS 1542 and BOSS 1441) at .
Our sample in the BOSS 1244 field consists of 20 galaxies with stellar-mass
ranging from to \Msun\ , star formation rate (SFR) from
10 to 240 \Msun\,yr, and global gas-phase metallicity (\oh) from 8.2 to
8.6. At confidence level, 2/20 galaxies in our sample show positive
(inverted) gradients -- the relative abundance of oxygen increasing with
galactocentric radius, opposite the usual trend. Furthermore, 1/20 shows
negative gradients and 17/20 are consistent with flat gradients. This high
fraction of flat/inverted gradients is uncommon in simulations and previous
observations conducted in blank fields at similar redshifts. To understand
this, we investigate the correlations among various observed properties of our
sample galaxies. We find an anticorrelation between metallicity gradient and
global metallicity of our galaxies residing in extreme overdensities, and a
marked deficiency of metallicity in our massive galaxies as compared to their
coeval field counterparts. We conclude that the cold-mode gas accretion plays
an active role in shaping the chemical evolution of galaxies in the
protocluster environments, diluting their central chemical abundance, and
flattening/inverting their metallicity gradients.Comment: 13 pages, 6 figures, 1 table. Accepted for publication in ApJ
An enhanced staining method K-B-2R staining for three-dimensional nerve reconstruction
BACKGROUND:Three-dimensional (3D) reconstruction of human peripheral nerves, as a useful tool to understand the nerve internal information and functional basis, has become an important area of research in the peripheral nerve field. METHODS:In this study, we proposed a two-dimensional (2D) Karnovsky-Roots toluidine blue ponceau 2R (K-B-2R) staining method based upon conventional Karnovsky-Roots staining. It significantly improved the ability to display nerve fascicles, motor and sensory nerve fiber textures. In this method, Karnovsky-Roots staining was carried out, followed by toluidine blue counterstain and ponceau 2R counterstain. RESULTS:Comparisons were conducted between the three methods in staining of median nerve sections, which showed similar distribution characters in acetylcholinesterase-positive sites. The additional counterstaining did not change the basis of Karnovsky-Roots staining. However, the resulting images from this new method significantly facilitated the subsequent 3D nerve reconstruction and 3D printing. CONCLUSIONS:These results show that the new staining method significantly enhanced the display qualities of nerve fascicle edges and fiber textures of motor and sensory nerves and facilitated 3D nerve reconstruction.Peng Luo, Jianghui Dong, Jian Qi, Yi Zhang, Xiaolin Liu, Yingchun Zhong, Cory J. Xian and Liping Wan
Three-dimensional reconstruction of peripheral nerve internal fascicular groups
Peripheral nerves are important pathways for receiving afferent sensory impulses and sending out efferent motor instructions, as carried out by sensory nerve fibers and motor nerve fibers. It has remained a great challenge to functionally reconnect nerve internal fiber bundles (or fascicles) in nerve repair. One possible solution may be to establish a 3D nerve fascicle visualization system. This study described the key technology of 3D peripheral nerve fascicle reconstruction. Firstly, fixed nerve segments were embedded with position lines, cryostat-sectioned continuously, stained and imaged histologically. Position line cross-sections were identified using a trained support vector machine method, and the coordinates of their central pixels were obtained. Then, nerve section images were registered using the bilinear method, and edges of fascicles were extracted using an improved gradient vector flow snake method. Subsequently, fascicle types were identified automatically using the multi-directional gradient and second-order gradient method. Finally, a 3D virtual model of internal fascicles was obtained after section images were processed. This technique was successfully applied for 3D reconstruction for the median nerve of the hand-wrist and cubital fossa regions and the gastrocnemius nerve. This nerve internal fascicle 3D reconstruction technology would be helpful for aiding peripheral nerve repair and virtual surgery.Yingchun Zhong, Liping Wang, Jianghui Dong, Yi Zhang, Peng Luo, Jian Qi,
Xiaolin Liu and Cory J. Xia
Strong quantum fluctuation of vortices in the new superconductor
By using transport and magnetic measurement, the upper critical field
and the irreversibility line has been determined. A
big separation between and has been found showing the
existence of a quantum vortex liquid state induced by quantum fluctuation of
vortices in the new superconductor . Further investigation on the
magnetic relaxation shows that both the quantum tunneling and the thermally
activated flux creep weakly depends on temperature. But when the melting field
is approached, a drastic rising of the relaxation rate is observed.
This may imply that the melting of the vortex matter at a finite temperature is
also induced by the quantum fluctuation of vortices.Comment: 4 pages, 4 figure
The effect of internal pressure on the tetragonal to monoclinic structural phase transition in ReOFeAs: the case of NdOFeAs
We report the temperature dependent x-ray powder diffraction of the
quaternary compound NdOFeAs (also called NdFeAsO) in the range between 300 K
and 95 K. We have detected the structural phase transition from the tetragonal
phase, with P4/nmm space group, to the orthorhombic or monoclinic phase, with
Cmma or P112/a1 (or P2/c) space group, over a broad temperature range from 150
K to 120 K, centered at T0 ~137 K. Therefore the temperature of this structural
phase transition is strongly reduced, by about ~30K, by increasing the internal
chemical pressure going from LaOFeAs to NdOFeAs. In contrast the
superconducting critical temperature increases from 27 K to 51 K going from
LaOFeAs to NdOFeAs doped samples. This result shows that the normal striped
orthorhombic Cmma phase competes with the superconducting tetragonal phase.
Therefore by controlling the internal chemical pressure in new materials it
should be possible to push toward zero the critical temperature T0 of the
structural phase transition, giving the striped phase, in order to get
superconductors with higher Tc.Comment: 9 pages, 3 figure
The accelerated scaling attractor solution of the interacting agegraphic dark energy in Brans-Dicke theory
We investigate the interacting agegraphic dark energy in Brans-Dicke theory
and introduce a new series general forms of dark sector coupling. As examples,
we select three cases involving a linear interaction form (Model I) and two
nonlinear interaction form (Model II and Model III). Our conclusions show that
the accelerated scaling attractor solutions do exist in these models. We also
find that these interacting agegraphic dark energy modes are consistent with
the observational data. The difference in these models is that nonlinear
interaction forms give more approached evolution to the standard CDM
model than the linear one. Our work implies that the nonlinear interaction
forms should be payed more attention.Comment: 9 pages, 10 figures, accepted in Eur. Phys. J.
Pairing symmetry and properties of iron-based high temperature superconductors
Pairing symmetry is important to indentify the pairing mechanism. The
analysis becomes particularly timely and important for the newly discovered
iron-based multi-orbital superconductors. From group theory point of view we
classified all pairing matrices (in the orbital space) that carry irreducible
representations of the system. The quasiparticle gap falls into three
categories: full, nodal and gapless. The nodal-gap states show conventional
Volovik effect even for on-site pairing. The gapless states are odd in orbital
space, have a negative superfluid density and are therefore unstable. In
connection to experiments we proposed possible pairing states and implications
for the pairing mechanism.Comment: 4 pages, 1 table, 2 figures, polished versio
Inhibition of Cardiac Sympathetic Afferent Reflex and Sympathetic Activity by Baroreceptor and Vagal Afferent Inputs in Chronic Heart Failure
BACKGROUND: Cardiac sympathetic afferent reflex (CSAR) contributes to sympathetic activation and angiotensin II (Ang II) in paraventricular nucleus (PVN) augments the CSAR in vagotomized (VT) and baroreceptor denervated (BD) rats with chronic heart failure (CHF). This study was designed to determine whether it is true in intact (INT) rats with CHF and to determine the effects of cardiac and baroreceptor afferents on the CSAR and sympathetic activity in CHF. METHODOLOGY/PRINCIPAL FINDINGS: Sham-operated (Sham) or coronary ligation-induced CHF rats were respectively subjected to BD+VT, VT, cardiac sympathetic denervation (CSD) or INT. Under anesthesia, renal sympathetic nerve activity (RSNA) and mean arterial pressure (MAP) were recorded, and the CSAR was evaluated by the RSNA and MAP responses to epicardial application of capsaicin. Either CSAR or the responses of RSNA, MAP and CSAR to Ang II in PVN were enhanced in CHF rats treated with BD+VT, VT or INT. Treatment with VT or BD+VT potentiated the CSAR and the CSAR responses to Ang II in both Sham and CHF rats. Treatment with CSD reversed the capsaicin-induced RSNA and MAP changes and the CSAR responses to Ang II in both Sham and CHF rats, and reduced the RSNA and MAP responses to Ang II only in CHF rats. CONCLUSIONS: The CSAR and the CSAR responses to Ang II in PVN are enhanced in intact CHF rats. Baroreceptor and vagal afferent activities inhibit CSAR and the CSAR responses to Ang II in intact Sham and CHF rats
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