809 research outputs found
Respiratory infections
A new European Respiratory Review series explores respiratory infections https://bit.ly/3A5eN3
Optimal stability and instability for near-linear Hamiltonians
In this paper, we will prove a very general result of stability for
perturbations of linear integrable Hamiltonian systems, and we will construct
an example of instability showing that both our result and our example are
optimal. Moreover, in the same spirit as the notion of KAM stable integrable
Hamiltonians, we will introduce a notion of effectively stable integrable
Hamiltonians, conjecture a characterization of these Hamiltonians and show that
our result prove this conjecture in the linear case
International Respiratory Infections Society COVID Research Conversations: Podcast 2 with Dr. Michael S. Niederman and Dr. Edward J. Schenck
Section(s) Topics
1–4 Introductions
5 COVID-19 in New York City
6–7 Telemedicine, long-term sequelae
8 Development of a multi-disciplinary ICU team
9–10 Treatment of ARDS, COVID-19 pathogenesis
11–12 Prioritizing treatment at research
13 Challenges in tracing the natural history of severe COVID-19
14–15 Experience with mechanically ventilated patients; non-pulmonary organ failure
16–17 Mapping COVID-19 trajectories by SOFA score
18–20 Findings: additive organ dysfunction, improving vs. worsening trajectory
21 ARDS therapeutic approaches
22 Clinical trials involving Cornell
23–25 Lessons learned: patient care, research, education, caring for critical care workers
26–30 2021 predictions: improved therapies and research, endemic COVID-19, vaccines
31–33 Prioritizing research projects at Cornell
34–38 Explanations for caseload reduction
39–43 Thanks and sign-of
Stability transitions for axisymmetric relative equilibria of Euclidean symmetric Hamiltonian systems
In the presence of noncompact symmetry, the stability of relative equilibria
under momentum-preserving perturbations does not generally imply robust
stability under momentum-changing perturbations. For axisymmetric relative
equilibria of Hamiltonian systems with Euclidean symmetry, we investigate
different mechanisms of stability: stability by energy-momentum confinement,
KAM, and Nekhoroshev stability, and we explain the transitions between these.
We apply our results to the Kirchhoff model for the motion of an axisymmetric
underwater vehicle, and we numerically study dissipation induced instability of
KAM stable relative equilibria for this system.Comment: Minor revisions. Typographical errors correcte
Double exponential stability of quasi-periodic motion in Hamiltonian systems
We prove that generically, both in a topological and measure-theoretical
sense, an invariant Lagrangian Diophantine torus of a Hamiltonian system is
doubly exponentially stable in the sense that nearby solutions remain close to
the torus for an interval of time which is doubly exponentially large with
respect to the inverse of the distance to the torus. We also prove that for an
arbitrary small perturbation of a generic integrable Hamiltonian system, there
is a set of almost full positive Lebesgue measure of KAM tori which are doubly
exponentially stable. Our results hold true for real-analytic but more
generally for Gevrey smooth systems
The Slippery Slope of MIS Academia: A Discussion of the Quest for Relevance in Our Discipline
The MIS discipline faces the need to periodically re-establish its relevance to both academics and practitioners. Evolving technology forces our discipline to change at a rate far exceeding that of other business disciplines. In the workplace, rapidly evolving IT management issues and technologies have led corporations to manage technical employees differently than other employees. In academia, however, MIS faculty are faced with the same expectations as other business faculty. The current model of MIS as an academic discipline has many issues that make staying current and relevant very difficult. The result is that MIS research and teaching lag practice. One might argue that as the field matures, we are falling further behind. This paper is the outcome of a panel discussion held during the 2006 Americas Conference on Information Systems in Acapulco, Mexico. The panel discussed the assertions that MIS is on a Slippery Slope that threatens our existence as a business discipline and that our current model encourages irrelevance, both in research and in teaching. Panel members were asked to share their views on five questions relative to the Slippery Slope from their unique perspectives
Effects of the protonophore carbonyl-cyanide m-chlorophenylhydrazone on intracytoplasmic membrane assembly in Rhodobacter sphaeroides
AbstractThe effect of carbonyl-cyanide m-chlorophenyl-hydrazone (CCCP) on intracytoplasmic membrane (ICM) assembly was examined in the purple bacterium Rhodobacter sphaeroides. CCCP blocks generation of the electrochemical proton gradient required for integral membrane protein insertion. ICM formation was induced for 8h, followed by a 4-h exposure to CCCP. Measurements of fluorescence induction/relaxation kinetics showed that CCCP caused a diminished quantum yield, a cessation in expansion of the functional absorption cross-section and a 4- to 10-fold slowing in the electron transfer turnover rate. ICM vesicles (chromatophores) and an upper-pigmented band (UPB) containing ICM growth initiation sites, were isolated and subjected to clear-native electrophoresis. Proteomic analysis of the chromatophore gel bands indicated that CCCP produced a 2.7-fold reduction in spectral counts in the preferentially assembled light-harvesting 2 (LH2) antenna, while the RC-LH1 complex, F1FO-ATPase and pyridine nucleotide transhydrogenase decreased by 1.7–1.9-fold. For 35 soluble enzymes, the ratio of 0.99 for treated/control proteins demonstrated that protein synthesis was unaffected by CCCP, suggesting that the membrane complex decline arose from the turnover of unassembled apoproteins. In the UPB fraction, an ~2-fold accumulation was observed for the preprotein translocase SecY, the SecA translocation ATPase, SecD and SecF insertion components, and chaperonins DnaJ and DnaK, consistent with the possibility that these factors, which act early in the assembly process, have accumulated in association with nascent polypeptides as stabilized assembly intermediates
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