2,183 research outputs found
Human pluripotent stem cell-derived mesenchymal stem cells prevent allergic airway inflammation in mice.
published_or_final_versio
Stable ultrahigh-density magneto-optical recordings using introduced linear defects
The stability of data bits in magnetic recording media at ultrahigh densities
is compromised by thermal `flips' -- magnetic spin reversals -- of nano-sized
spin domains, which erase the stored information. Media that are magnetized
perpendicular to the plane of the film, such as ultrathin cobalt films or
multilayered structures, are more stable against thermal self-erasure than
conventional memory devices. In this context, magneto-optical memories seem
particularly promising for ultrahigh-density recording on portable disks, and
bit densities of 100 Gbit inch have been demonstrated using recent
advances in the bit writing and reading techniques. But the roughness and
mobility of the magnetic domain walls prevents closer packing of the magnetic
bits, and therefore presents a challenge to reaching even higher bit densities.
Here we report that the strain imposed by a linear defect in a magnetic thin
film can smooth rough domain walls over regions hundreds of micrometers in
size, and halt their motion. A scaling analysis of this process, based on the
generic physics of disorder-controlled elastic lines, points to a simple way by
which magnetic media might be prepared that can store data at densities in
excess of 1 Tbit inch.Comment: 5 pages, 4 figures, see also an article in TRN News at
http://www.trnmag.com/Stories/041801/Defects_boost_disc_capacity_041801.htm
Coherent spinor dynamics in a spin-1 Bose condensate
Collisions in a thermal gas are perceived as random or incoherent as a
consequence of the large numbers of initial and final quantum states accessible
to the system. In a quantum gas, e.g. a Bose-Einstein condensate or a
degenerate Fermi gas, the phase space accessible to low energy collisions is so
restricted that collisions be-come coherent and reversible. Here, we report the
observation of coherent spin-changing collisions in a gas of spin-1 bosons.
Starting with condensates occupying two spin states, a condensate in the third
spin state is coherently and reversibly created by atomic collisions. The
observed dynamics are analogous to Josephson oscillations in weakly connected
superconductors and represent a type of matter-wave four-wave mixing. The
spin-dependent scattering length is determined from these oscillations to be
-1.45(18) Bohr. Finally, we demonstrate coherent control of the evolution of
the system by applying differential phase shifts to the spin states using
magnetic fields.Comment: 19 pages, 3 figure
Single vortex-antivortex pair in an exciton polariton condensate
In a homogeneous two-dimensional system at non-zero temperature, although
there can be no ordering of infinite range, a superfluid phase is predicted for
a Bose liquid. The stabilization of phase in this superfluid regime is achieved
by the formation of bound vortex-antivortex pairs. It is believed that several
different systems share this common behaviour, when the parameter describing
their ordered state has two degrees of freedom, and the theory has been tested
for some of them. However, there has been no direct experimental observation of
the phase stabilization mechanism by a bound pair. Here we present an
experimental technique that can identify a single vortex-antivortex pair in a
two-dimensional exciton polariton condensate. The pair is generated by the
inhomogeneous pumping spot profile, and is revealed in the time-integrated
phase maps acquired using Michelson interferometry, which show that the
condensate phase is only locally disturbed. Numerical modelling based on open
dissipative Gross-Pitaevskii equation suggests that the pair evolution is quite
different in this non-equilibrium system compared to atomic condensates. Our
results demonstrate that the exciton polariton condensate is a unique system
for studying two-dimensional superfluidity in a previously inaccessible regime
Giant Superfluorescent Bursts from a Semiconductor Magnetoplasma
Currently, considerable resurgent interest exists in the concept of
superradiance (SR), i.e., accelerated relaxation of excited dipoles due to
cooperative spontaneous emission, first proposed by Dicke in 1954. Recent
authors have discussed SR in diverse contexts, including cavity quantum
electrodynamics, quantum phase transitions, and plasmonics. At the heart of
these various experiments lies the coherent coupling of constituent particles
to each other via their radiation field that cooperatively governs the dynamics
of the whole system. In the most exciting form of SR, called superfluorescence
(SF), macroscopic coherence spontaneously builds up out of an initially
incoherent ensemble of excited dipoles and then decays abruptly. Here, we
demonstrate the emergence of this photon-mediated, cooperative, many-body state
in a very unlikely system: an ultradense electron-hole plasma in a
semiconductor. We observe intense, delayed pulses, or bursts, of coherent
radiation from highly photo-excited semiconductor quantum wells with a
concomitant sudden decrease in population from total inversion to zero. Unlike
previously reported SF in atomic and molecular systems that occur on nanosecond
time scales, these intense SF bursts have picosecond pulse-widths and are
delayed in time by tens of picoseconds with respect to the excitation pulse.
They appear only at sufficiently high excitation powers and magnetic fields and
sufficiently low temperatures - where various interactions causing decoherence
are suppressed. We present theoretical simulations based on the relaxation and
recombination dynamics of ultrahigh-density electron-hole pairs in a quantizing
magnetic field, which successfully capture the salient features of the
experimental observations.Comment: 21 pages, 4 figure
Towards the development of novel Trypanosoma brucei RNA editing ligase 1 inhibitors
Abstract Background Trypanosoma brucei (T. brucei) is an infectious agent for which drug development has been largely neglected. We here use a recently developed computer program called AutoGrow to add interacting molecular fragments to S5, a known inhibitor of the validated T. brucei drug target RNA editing ligase 1, in order to improve its predicted binding affinity. Results The proposed binding modes of the resulting compounds mimic that of ATP, the native substrate, and provide insights into novel protein-ligand interactions that may be exploited in future drug-discovery projects. Conclusions We are hopeful that these new predicted inhibitors will aid medicinal chemists in developing novel therapeutics to fight human African trypanosomiasis
Centralizer's applications to the (b, c)-inverses in rings
[EN] We give several conditions in order that the absorption law for one sided (b,c)-inverses in rings holds. Also, by using centralizers, we obtain the absorption law for the (b,c)-inverse and the reverse order law of the (b,c)-inverse in rings. As applications, we obtain the related results for the inverse along an element, Moore-Penrose inverse, Drazin inverse, group inverse and core inverse.This research is supported by the National Natural Science Foundation of China (no. 11771076 and no. 11871301). The first author is grateful to China Scholarship Council for giving him a scholarship for his further study in Universitat Politecnica de Valencia, Spain.Xu, S.; Chen, J.; Benítez López, J.; Wang, D. (2019). Centralizer's applications to the (b, c)-inverses in rings. Revista de la Real Academia de Ciencias Exactas, Físicas y Naturales. 113(3):1739-1746. https://doi.org/10.1007/s13398-018-0574-0S173917461133Baksalary, O.M., Trenkler, G.: Core inverse of matrices. Linear Multilinear Algebra 58(6), 681–697 (2010)Benítez, J., Boasso, E.: The inverse along an element in rings with an involution, Banach algebras and C ∗ -algebras. Linear Multilinear Algebra 65(2), 284–299 (2017)Benítez, J., Boasso, E., Jin, H.W.: On one-sided ( B , C ) -inverses of arbitrary matrices. Electron. J. Linear Algebra 32, 391–422 (2017)Boasso, E., Kantún-Montiel, G.: The ( b , c ) -inverses in rings and in the Banach context. Mediterr. J. Math. 14, 112 (2017)Chen, Q.G., Wang, D.G.: A class of coquasitriangular Hopf group algebras. Comm. Algebra 44(1), 310–335 (2016)Chen, J.L., Ke, Y.Y., Mosić, D.: The reverse order law of the ( b , c ) -inverse in semigroups. Acta Math. Hung. 151(1), 181–198 (2017)Deng, C.Y.: Reverse order law for the group inverses. J. Math. Anal. Appl. 382(2), 663–671 (2011)Drazin, M.P.: Pseudo-inverses in associative rings and semigroups. Am. Math. Mon. 65, 506–514 (1958)Drazin, M.P.: A class of outer generalized inverses. Linear Algebra Appl. 436, 1909–1923 (2012)Drazin, M.P.: Left and right generalized inverses. Linear Algebra Appl. 510, 64–78 (2016)Jin, H.W., Benítez, J.: The absorption laws for the generalized inverses in rings. Electron. J. Linear Algebra 30, 827–842 (2015)Johnson, B.E.: An introduction to the theory of centralizers. Proc. Lond. Math. Soc. 14, 299–320 (1964)Ke, Y.Y., Cvetković-Ilić, D.S., Chen, J.L., Višnjić, J.: New results on ( b , c ) -inverses. Linear Multilinear Algebra 66(3), 447–458 (2018)Ke Y.Y., Višnjić J., Chen J.L.: One sided ( b , c ) -inverse in rings (2016). arXiv:1607.06230v1Liu, X.J., Jin, H.W., Cvetković-Ilić, D.S.: The absorption laws for the generalized inverses. Appl. Math. Comput. 219, 2053–2059 (2012)Mary, X.: On generalized inverse and Green’s relations. Linear Algebra Appl. 434, 1836–1844 (2011)Mary, X., Patrício, P.: Generalized inverses modulo H in semigroups and rings. Linear Multilinear Algebra 61(8), 1130–1135 (2013)Mosić, D., Cvetković-Ilić, D.S.: Reverse order law for the Moore-Penrose inverse in C ∗ -algebras. Electron. J. Linear Algebra 22, 92–111 (2011)Rakić, D.S.: A note on Rao and Mitra’s constrained inverse and Drazin’s ( b , c ) -inverse. Linear Algebra Appl. 523, 102–108 (2017)Rakić, D.S., Dinčić, N.Č., Djordjević, D.S.: Group, Moore–Penrose, core and dual core inverse in rings with involution. Linear Algebra Appl. 463, 115–133 (2014)Wang, L., Castro-González, N., Chen, J.L.: Characterizations of outer generalized inverses. Can. Math. Bull. 60(4), 861–871 (2017)Wei, Y.M.: A characterization and representation of the generalized inverse A T , S ( 2 ) and its applications. Linear Algebra Appl. 280, 87–96 (1998)Xu, S.Z., Benítez, J.: Existence criteria and expressions of the ( b , c ) -inverse in rings and its applications. Mediterr. J. Math. 15, 14 (2018)Zhu, H.H., Chen, J.L., Patrício, P.: Further results on the inverse along an element in semigroups and rings. Linear Multilinear Algebra 64(3), 393–403 (2016)Zhu, H.H., Chen, J.L., Patrício, P.: Reverse order law for the inverse along an element. Linear Multilinear Algebra 65, 166–177 (2017)Zhu, H.H., Chen, J.L., Patrício, P., Mary, X.: Centralizer’s applications to the inverse along an element. Appl. Math. Comput. 315, 27–33 (2017)Zhu, H.H., Zhang, X.X., Chen, J.L.: Centralizers and their applications to generalized inverses. Linear Algebra Appl. 458, 291–300 (2014
Fish oil replacement in current aquaculture feed : is cholesterol a hidden treasure for fish nutrition?
Teleost fish, as with all vertebrates, are capable of synthesizing cholesterol and as such have no dietary requirement for it. Thus, limited research has addressed the potential effects of dietary cholesterol in fish, even if fish meal and fish oil are increasingly replaced by vegetable alternatives in modern aquafeeds, resulting in progressively reduced dietary cholesterol content. The objective of this study was to determine if dietary cholesterol fortification in a vegetable oil-based diet can manifest any effects on growth and feed utilization performance in the salmonid fish, the rainbow trout. In addition, given a series of studies in mammals have shown that dietary cholesterol can directly affect the fatty acid metabolism, the apparent in vivo fatty acid metabolism of fish fed the experimental diets was assessed. Triplicate groups of juvenile fish were fed one of two identical vegetable oil-based diets, with additional cholesterol fortification (high cholesterol, H-Chol) or without (low cholesterol, L-Chol), for 12 weeks. No effects were observed on growth and feed efficiency, however, in fish fed H-Col no biosynthesis of cholesterol, and a remarkably decreased apparent in vivo fatty acid b-oxidation were recorded, whilst in LChol fed fish, cholesterol was abundantly biosynthesised and an increased apparent in vivo fatty acid b-oxidation was observed. Only minor effects were observed on the activity of stearyl-CoA desaturase, but a significant increase was observed for both the transcription rate in liver and the apparent in vivo activity of the fatty acid D-6 desaturase and elongase, with increasing dietary cholesterol. This study showed that the possible effects of reduced dietary cholesterol in current aquafeeds can be significant and warrant future investigations
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