1,816 research outputs found
Extended Hubbard Model with Unconventional Pairing in Two Dimensions
We rigorously prove that an extended Hubbard model with attraction in two
dimensions has an unconventional pairing ground state for any electron filling.
The anisotropic spin-0 or anisotropic spin-1 pairing symmetry is realized,
depending on a phase parameter characterizing the type of local attractive
interactions. In both cases the ground state is unique. It is also shown that
in a special case, where there are no electron hopping terms, the ground state
has Ising-type N\'eel order at half-filling, when on-site repulsion is
furthermore added. Physical applications are mentioned.Comment: 5 pages, 2 figures, v2: title is changed, new results are added,
minor change
Site-selective NMR for odd-frequency Cooper pairs around vortex in chiral p-wave superconductors
In order to identify the pairing symmetry with chirality, we study
site-selective NMR in chiral p-wave superconductors. We calculate local nuclear
relaxation rate 1/T_1 in the vortex lattice state by Eilenberger theory,
including the applied magnetic field dependence. We find that 1/T_1 in the NMR
resonance line shape is different between two chiral states
p_{pm}(=p_x{pm}ip_y), depending on whether the chirality is parallel or
anti-parallel to the vorticity. Anomalous suppression of 1/T_1 occurs around
the vortex core in the chiral p_- wave due to the negative coherence term
coming from the odd-frequency s-wave Cooper pair induced around the vortex with
Majorana state.Comment: 6 pages, 4 figure
Polar relaxation by dynein-mediated removal of cortical myosin II
Nearly 6 decades ago, Lewis Wolpert proposed the relaxation of the polar cell cortex by the radial arrays of astral microtubules as a mechanism for cleavage furrow induction (White and Borisy, 1983; Wolpert, 1960). While this mechanism has remained controversial (Rappaport, 1996), recent work has provided evidence for polar relaxation by astral microtubules (Chen et al., 2008; Dechant and Glotzer, 2003; Foe and Dassow, 2008; Murthy and Wadsworth, 2008; Werner et al., 2007), although its molecular mechanisms remain elusive. Here, using C. elegans embryos, we show that polar relaxation is achieved through dynein-mediated removal of myosin II from the polar cortexes. Mutants that position centrosomes closer to the polar cortex accelerated furrow induction whereas suppression of dynein activity delayed furrowing. We provide evidence that dynein-mediated removal of myosin II from the polar cortexes triggers cortical flow towards the cell equator, which induces the assembly of the actomyosin contractile ring. These studies for the first time provide a molecular basis for the aster-dependent polar relaxation, which works in parallel with equatorial stimulation to promote robust cytokinesis
Vortex state in double transition superconductors
Novel vortex phase and nature of double transition field are investigated by
two-component Ginzburg-Landau theory in a situation where fourfold-twofold
symmetric superconducting double transition occurs. The deformation from 60
degree triangular vortex lattice and a possibility of the vortex sheet
structure are discussed. In the presence of the gradient coupling, the
transition changes to a crossover at finite fields. These characters are
important to identify the multiple superconducting phase in PrOs_4_Sb_12.Comment: 4 pages, 4 figures, to appear in Phys. Rev. Let
Соотношение путей углеводного синтеза при введении свободных и фосфорилированных сахаров в листья картофеля
Показано, что регуляция путей биосинтеза углеводов может осуществляться через изменение концентрации промежуточных и конечных метаболитов. При этом одним из факторов, регулирующих направленность синтеза углеводов, является активность АДФГ- и УДФГ-пирофосфорилаз. По-видимому, регуляция работы этих ферментов может осуществляться низкомолекулярными метаболитами по принципу обратной связи
Enantioselective Organocatalytic Amine Conjugate Addition
The first enantioselective organocatalytic amine conjugate addition has been successfully developed. The application of LUMO-lowering iminium catalysis has enabled the highly chemo- and enantioselective 1,4-addition of a rationally designed N-silyloxycarbamate nucleophile (HOMO-raised) to α,β-unsaturated aldehydes. Imidazolidinone 2•pTSA was found to catalyze the addition of various orthogonally N-protected silyloxycarbamate nucleophiles to a range of α,β-unsaturated aldehydes, affording synthetically useful β-amino aldehyde intermediates. The synthetic utility of the protocol was demonstrated in the rapid synthesis of enantioenriched β-amino acids in one operation and 1,3-amino alcohol derivatives in three operations
Removal of Antibiotic Resistance Genes in an Anaerobic Membrane Bioreactor Treating Primary Clarifier Effluent at 20 °C
Anaerobic membrane bioreactors (AnMBR) play a key role in future plans for sustainable wastewater treatment and resource recovery because they have no energy-intensive oxygen transfer requirements and can produce biomethane for renewable energy. Recent research results show that they can meet relatively stringent discharge limits with respect to BOD5 and TSS when treating municipal wastewater primary effluent. Sustainable used water recovery plans should also consider removal of unregulated pollutants. Antibiotic resistance genes (ARGs) represent an important emerging contaminant due to public health concerns surrounding the spread of infections resistant to common antibiotics. Conventional activated sludge processes have demonstrated mixed results regarding ARG removal. The objective of this research was to determine the impact of an AnMBR on ARG removal when treating municipal primary clarifier effluent at 20 °C. AnMBR treatment resulted in 3.3 to 3.6 log reduction of ARG and the horizontal gene transfer determinate, intI1, copies in filtrate. Membrane treatment significantly decreased the total biomass as indicated by a decrease in 16S rRNA gene concentration. Microbial community analysis via Illumina sequencing revealed that the relative abundance of putative pathogens was higher in membrane filtrate compared to primary effluent although the overall bacterial 16S rRNA gene concentrations was lower in filtrate. Membrane treatment also substantially reduced microbial diversity in filtrate compared to anaerobic reactor contents
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