5,754 research outputs found
Rhodium and copper 6-methylpicolinate complexes. Structural diversity and supramolecular interaction study
Seven new coordination compounds with 6-methylpicolinic acid (6-HMepic) and rhodium(III) or copper(II) of formula [Rh(6-Mepic)3] (1), [Rh(6-Mepic)2(H2O)Cl] (2), [Rh(6-HMepic)(6-Mepic)Cl2]·3.5(H2O) (3), [Cu(6-Mepic)2(H2O)]·H2O (4), [Cu(6-Mepic)2]n, (5), [Cu(6-Mepic)(6-HMepic)I] (6) and [Cu(6-Mepic)(6-HMepic)Cl] (7) have been obtained. Their syntheses have been rationalized, and their structural and supramolecular characteristics have been studied and compared with other similar rhodium and copper picolinate complexes previously reported, in order to stablish structural correlations and analogies. The electrical properties of coordination polymer [Cu(6-Mepic)2]n (5) have been also analyzed and it has been found that it shows a moderated electrical transport along the chain.We thank the financial support from the Spanish Ministerio de EconomĂa y Competitividad (MAT2013-46502-C2-2P and MAT2013-46753-C2-1P). Also the scientific computing center (CCC) of the Autonoma University of Madrid for their tim
Guaranteed emergence of genuine entanglement in 3-qubit evolving systems
Multipartite entanglement has been shown to be of particular relevance for a
better understanding and exploitation of the dynamics and flow of entanglement
in multiparty systems. This calls for analysis aimed at identifying the
appropriate processes that guarantee the emergence of multipartite entanglement
in a wide range of scenarios. Here we carry on such analysis considering a
system of two initially entangled qubits, one of which is let to interact with
a third qubit according to an arbitrary unitary evolution. We establish
necessary and sufficient conditions on the corresponding Kraus operators, to
discern whether the evolved state pertains to either one of the classes of
3-qubit pure states that exhibit some kind of entanglement, namely biseparable,
W-, and GHZ- genuine entangled classes. Our results provide a classification of
the Kraus operators according to their capacity of producing 3-qubit
entanglement, and pave the way for extending the analysis to larger systems and
determining the particular interactions that must be implemented in order to
create, enhance and distribute entanglement in a specific manner.Comment: Two new subsections included. Accepted for publication in The
European Physical Journal
MasterChem: Cooking 2D-polymers
2D-polymers are still dominated by graphene and closely related materials such as boron nitride, transition metal sulphides and oxides. However, the rational combination of molecules with suitable design is already showing the high potential of chemistry in this new research field. The aim of this feature article is to illustrate, and provide some perspectives, the current state-of-the-art in the field of synthetic 2D-polymers showing different alternatives to prepare this novel type of polymers based on the rational use of chemistry. This review comprises a brief revision of the essential concepts, the strategies of preparation following the two general approaches, bottom-up and top-down, and a revision of the promising seminal properties showed by some of these nanomaterials.Financial support from Spanish MINECO (MAT2013-46753-C2-1-P and MAT2013-46502-C2-2-P). D. R. thanks the Spanish MECD for a FPU gran
Polydispersity Effects in the Dynamics and Stability of Bubbling Flows
The occurrence of swarms of small bubbles in a variety of industrial systems
enhances their performance. However, the effects that size polydispersity may
produce on the stability of kinematic waves, the gain factor, mean bubble
velocity, kinematic and dynamic wave velocities is, to our knowledge, not yet
well established. We found that size polydispersity enhances the stability of a
bubble column by a factor of about 23% as a function of frequency and for a
particular type of bubble column. In this way our model predicts effects that
might be verified experimentally but this, however, remain to be assessed. Our
results reinforce the point of view advocated in this work in the sense that a
description of a bubble column based on the concept of randomness of a bubble
cloud and average properties of the fluid motion, may be a useful approach that
has not been exploited in engineering systems.Comment: 11 pages, 2 figures, presented at the 3rd NEXT-SigmaPhi International
Conference, 13-18 August, 2005, Kolymbari, Cret
Layered Quantum Hall Insulators with Ultracold Atoms
We consider a generalization of the 2-dimensional (2D) quantum-Hall insulator
to a non-compact, non-Abelian gauge group, the Heisenberg-Weyl group. We show
that this kind of insulator is actually a layered 3D insulator with nontrivial
topology. We further show that nontrivial combinations of quantized transverse
conductivities can be engineered with the help of a staggered potential. We
investigate the robustness and topological nature of this conductivity and
connect it to the surface modes of the system. We also propose a simple
experimental realization with ultracold atoms in 3D confined to a 2D square
lattice with the third dimension being mapped to a gauge coordinate.Comment: 6 page
Vortices on demand in multicomponent Bose-Einstein condensates
We present a simple mechanism to produce vortices at any desired spatial
locations in harmonically trapped Bose-Einstein condensates (BEC) with
multicomponent spin states coupled to external transverse and axial magnetic
fields. The vortices appear at the spatial points where the spin-transverse
field interaction vanishes and, depending on the multipolar magnetic field
order, the vortices can acquire different predictable topological charges. We
explicitly demonstrate our findings, both numerically and analytically, by
analyzing a 2D BEC via the Gross-Pitaevskii equation for atomic systems with
either two or three internal states. We further show that, by an spontaneous
symmetry breaking mechanism, vortices can appear in any spin component, unless
symmetry is externally broken at the outset by an axial field. We suggest that
this scenario may be tested using an ultracold gas of Rb occupying all
three states in an optical trap.Comment: 11 pages, 9 figures, (Accepted in PRA
A mutation in the centriole-associated protein centrin causes genomic instability via increased chromosome loss in Chlamydomonas reinhardtii
BACKGROUND: The role of centrioles in mitotic spindle function remains unclear. One approach to investigate mitotic centriole function is to ask whether mutation of centriole-associated proteins can cause genomic instability. RESULTS: We addressed the role of the centriole-associated EF-hand protein centrin in genomic stability using a Chlamydomonas reinhardtii centrin mutant that forms acentriolar bipolar spindles and lacks the centrin-based rhizoplast structures that join centrioles to the nucleus. Using a genetic assay for loss of heterozygosity, we found that this centrin mutant showed increased genomic instability compared to wild-type cells, and we determined that the increase in genomic instability was due to a 100-fold increase in chromosome loss rates compared to wild type. Live cell imaging reveals an increased rate in cell death during G1 in haploid cells that is consistent with an elevated rate of chromosome loss, and analysis of cell death versus centriole copy number argues against a role for multipolar spindles in this process. CONCLUSION: The increased chromosome loss rates observed in a centrin mutant that forms acentriolar spindles suggests a role for centrin protein, and possibly centrioles, in mitotic fidelity
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