6,964 research outputs found
The spontaneous emergence of ordered phases in crumpled sheets
X-ray tomography is performed to acquire 3D images of crumpled aluminum
foils. We develop an algorithm to trace out the labyrinthian paths in the three
perpendicular cross sections of the data matrices. The tangent-tangent
correlation function along each path is found to decay exponentially with an
effective persistence length that shortens as the crumpled ball becomes more
compact. In the mean time, we observed ordered domains near the crust, similar
to the lamellae phase mixed by the amorphous portion in lyotropic liquid
crystals. The size and density of these domains grow with further compaction,
and their orientation favors either perpendicular or parallel to the radial
direction. Ordering is also identified near the core with an arbitrary
orientation, exemplary of the spontaneous symmetry breaking
Singularity-free Guiding Vector Field for Robot Navigation
Most of the existing path-following navigation algorithms cannot guarantee
global convergence to desired paths or enable following self-intersected
desired paths due to the existence of singular points where navigation
algorithms return unreliable or even no solutions. One typical example arises
in vector-field guided path-following (VF-PF) navigation algorithms. These
algorithms are based on a vector field, and the singular points are exactly
where the vector field diminishes. In this paper, we show that it is
mathematically impossible for conventional VF-PF algorithms to achieve global
convergence to desired paths that are self-intersected or even just simple
closed (precisely, homeomorphic to the unit circle). Motivated by this new
impossibility result, we propose a novel method to transform self-intersected
or simple closed desired paths to non-self-intersected and unbounded
(precisely, homeomorphic to the real line) counterparts in a higher-dimensional
space. Corresponding to this new desired path, we construct a singularity-free
guiding vector field on a higher-dimensional space. The integral curves of this
new guiding vector field is thus exploited to enable global convergence to the
higher-dimensional desired path, and therefore the projection of the integral
curves on a lower-dimensional subspace converge to the physical
(lower-dimensional) desired path. Rigorous theoretical analysis is carried out
for the theoretical results using dynamical systems theory. In addition, we
show both by theoretical analysis and numerical simulations that our proposed
method is an extension combining conventional VF-PF algorithms and trajectory
tracking algorithms. Finally, to show the practical value of our proposed
approach for complex engineering systems, we conduct outdoor experiments with a
fixed-wing airplane in windy environment to follow both 2D and 3D desired
paths.Comment: Accepted for publication in IEEE Trransactions on Robotics (T-RO
Effect of Alisma plantago-aquatica Linn extract on hyperprolactinemia in rats
Purpose: To investigate the anti-hyperprolactinemia effect and mechanism of action of of Alisma plantago-aquatica Linn. extract (APLE) in rats.
Methods: The hyperprolactinemia (hyperPRL) model of rats was established by intraperitoneal (i.p.) metoclopramide (200 mg/kg daily) for 10 days. Sixty rats were divided into six groups (n = 10 each): normal group), hyperPRL control group, hyperPRL plus 0.6 mg/kg bromocriptine (as a positive control) group, and hyperPRL plus high (14.4 g/kg), medium (7.2 g/kg), or low (3.6 g/kg) dose of APLE. Bromocriptine or vehicle control was administered to the rats daily for 30 days, and the hypothalamus dopamine D2 receptor, protein kinase A (PKA), and cyclic adenosine monophosphate (cAMP) levels were investigated by Western blot.
Results: Compared with the normal rats, hypothalamus dopamine D2 receptor protein expression was significantly lower in hyperPRL rats (p < 0.01), but was changed significantly after 30-day doses (various) of APLE administration (3.6 g/kg, p < 0.05; 7.2 and 14.4 g/kg, p < 0.01). Compared with the control rats, hypothalamus PKA and cAMP levels were significantly higher in hyperPRL rats (p < 0.01). These increases in PKA and cAMP were significantly attenuated by 30-day of bromocriptine treatment or various doses of APLE (p < 0.01).
Conclusion: The anti-hyperPRL activity of APLE is confirmed from the findings of this study Thus, the plant can potentially be developed into a new anti-hyperprolactinemia drug
Highly efficient genome editing using oocyte-specific zcas9 transgenic zebrafish.Liu Y, Zhang C, Zhang Y, Lin S, Shi DL, Shao M
International audienceHighly efficient genome editing using oocyte-specific zcas9 transgenic zebrafish Since its first application to induce mutations in mammalian cells (Cong et al., 2013; Mali et al., 2013), CRISPR/Cas9 rapidly becomes a routine technique to perform genome editing in a variety of biological systems due to its facile, robust, and multiplexable features (Hwang et al., 2013; Guo et al., 2014; Wang et al., 2013). In every system, Cas9 and sgRNA should co-express to induce mutations. This is typically achieved by injection of the sgRNA mixed with Cas9 mRNA or protein into the fertilized eggs in zebrafish. As the in vivo translation of capped RNAs delay the presence of sufficient Cas9 protein, the mRNA injection produces more mosaic animals and shows relatively lower efficiency when compared to Cas9 protein injection (Burger et al., 2016). However, it is much more cost effective than using commercially available Cas9 protein, especially in the case of large-scale mutation screens. To further simplify this procedure, lower the cost and maintain an acceptable high genome editing efficiency in zebrafish, we set out to generate a transgenic line with stable and specific Cas9 expression in the egg. zpc (zp3b) promoter (zpc0.5) was reported to drive robust and specific GFP expression in the oocyte (Onichtchouk et al., 2003), we thus fused it with a zebrafish codon optimized cas9 (zcas9) followed by an SV40 3' UTR (Fig. 1A and File S1; Liu et al., 2014), and introduced this construct to zebrafish genome by Tol2 mediated transgenesis (Urasaki et al., 2006). To screen female F0 fish harboring this transgene, the F0 female founders were outcrossed with the wild-type male, the resulting eggs were injected with an sgRNA targeting slc45a2 (Moreno-Mateos et al., 2015), a gene essential for melanin synthesis, and assayed for their pigmentation phenotype. We found that the offspring of one founder showed a high proportion of pigmentation defect. Some of them exhibited a homozygous mutant like albino phenotype, suggesting a robust Cas9 expression in the egg and a very high efficient gene disruption. To examine the specificity of zcas9 expression in the transgenic line, the offspring (F1) of this F0 founder were raised to adulthood, and the ovaries of female F1 transgenic fish were dissected and subjected to in situ hybridization (ISH) employing the probe of zcas9. We found that the transcripts of zcas9 were specifically distributed in oocytes with a diameter of 40-200 µm, at around IB-II stages, while in WT embryos, no hybridization signals were detected (Fig. 1B, C). We did not detect zcas9 expression in stage IA oocytes or in larger ones after stage II. Accordingly, by RT-PCR, we also faile
Poly[[μ2-aqua-tetraaquadi-μ3-malonato-nickel(II)strontium(II)] dihydrate]
The unit-cell parameters for the title mixed-metal coordination polymer, {[NiSr(C3H2O4)2(H2O)5]·2H2O}n, which is isostructural with its Co-containing analogue, were reported previously [Gil de Muro et al. (1999 ▶). Eur. J. Inorg. Chem. pp. 935–943]; the full crystal structure including a description of the hydrogen bonding is reported here. The Sr2+ ion is bonded to five O atoms from three different malonate dianions and four water molecules, displaying a distorted tricapped trigonal–prismatic coordination geometry. Two malonate dianions, two water molecules and one Ni2+ ion build up a dianionic [Ni(C3H2O4)2(H2O)2]2− unit incorporating a slightly distorted NiO6 octahedron, which coordinates to three nearby Sr2+ ions. This arrangement creates a metal-organic framework having a 20-membered ring with four Ni and six Sr atoms lying in the bc plane. The coordinated and uncoordinated water molecules are responsible for the formation of two D5 hydrogen-bonded water chains within the 20-membered ring and they are linked into an R4 water cluster via two bifurcated O—H⋯(O,O) links
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