222 research outputs found
A nilpotent IP polynomial multiple recurrence theorem
We generalize the IP-polynomial Szemer\'edi theorem due to Bergelson and
McCutcheon and the nilpotent Szemer\'edi theorem due to Leibman. Important
tools in our proof include a generalization of Leibman's result that polynomial
mappings into a nilpotent group form a group and a multiparameter version of
the nilpotent Hales-Jewett theorem due to Bergelson and Leibman.Comment: v4: switch to TeXlive 2016 and biblate
Uniformity in the Wiener-Wintner theorem for nilsequences
We prove a uniform extension of the Wiener-Wintner theorem for nilsequences
due to Host and Kra and a nilsequence extension of the topological
Wiener-Wintner theorem due to Assani. Our argument is based on (vertical)
Fourier analysis and a Sobolev embedding theorem.Comment: v3: 18 p., proof that the cube construction produces compact
homogeneous spaces added, measurability issues in the proof of Theorem 1.5
addressed. We thank the anonymous referees for pointing out these gaps in v
Linear forms and quadratic uniformity for functions on
A very useful fact in additive combinatorics is that analytic expressions
that can be used to count the number of structures of various kinds in subsets
of Abelian groups are robust under quasirandom perturbations, and moreover that
quasirandomness can often be measured by means of certain easily described
norms, known as uniformity norms. However, determining which uniformity norms
work for which structures turns out to be a surprisingly hard question. In
[GW09a] and [GW09b, GW09c] we gave a complete answer to this question for
groups of the form , provided is not too small. In
, substantial extra difficulties arise, of which the most
important is that an "inverse theorem" even for the uniformity norm
requires a more sophisticated (local) formulation. When is
prime, is not rich in subgroups, so one must use regular Bohr
neighbourhoods instead. In this paper, we prove the first non-trivial case of
the main conjecture from [GW09a].Comment: 66 page
The rice NLR pair Pikp-1/Pikp-2 initiates cell death through receptor cooperation rather than negative regulation
Plant NLR immune receptors are multidomain proteins that can function as specialized sensor/helper pairs. Paired NLR immune receptors are generally thought to function via negative regulation, where one NLR represses the activity of the second and detection of pathogen effectors relieves this repression to initiate immunity. However, whether this mechanism is common to all NLR pairs is not known. Here, we show that the rice NLR pair Pikp-1/Pikp-2, which confers resistance to strains of the blast pathogen Magnaporthe oryzae (syn. Pyricularia oryzae) expressing the AVR-PikD effector, functions via receptor cooperation, with effector-triggered activation requiring both NLRs to trigger the immune response. To investigate the mechanism of Pikp-1/Pikp-2 activation, we expressed truncated variants of these proteins, and made mutations in previously identified NLR sequence motifs. We found that any domain truncation, in either Pikp-1 or Pikp-2, prevented cell death in the presence of AVR-PikD, revealing that all domains are required for activity. Further, expression of individual Pikp-1 or Pikp-2 domains did not result in cell death. Mutations in the conserved P-loop and MHD sequence motifs in both Pikp-1 and Pikp-2 prevented cell death activation, demonstrating that these motifs are required for the function of the two partner NLRs. Finally, we showed that Pikp-1 and Pikp-2 associate to form homo- and hetero-complexes in planta in the absence of AVR-PikD; on co-expression the effector binds to Pikp-1 generating a tri-partite complex. Taken together, we provide evidence that Pikp-1 and Pikp-2 form a fine-tuned system that is activated by AVR-PikD via receptor cooperation rather than negative regulation
Esophagectomy without mortality: What can surgeons do?
Introduction: Surgical resection remains the mainstay treatment for patients with localized esophageal cancer. It is, however, a complex procedure. Mortality rate used to be high, but in recent years, death rate has been reduced to below 5% in specialized centers. Methods: Outcome of esophagectomy can be improved by paying attention to (1) appropriate patient section, (2) choice of surgical techniques and their execution, and (3) optimizing perioperative care. A volume-outcome relationship is also evident. Surgeons can perform esophagectomy without mortality, but a multi-disciplinary team management is essential to achieve this goal. © 2009 The Society for Surgery of the Alimentary Tract.postprin
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