7,093 research outputs found
LOWER BOUNDS FOR THE BUCKLING PRESSURE OF SPHERICAL SHELLS
Hydrostatic buckling pressure calculations for spherical shell
Bifurcation structures and transient chaos in a four-dimensional Chua model
A four-dimensional four-parameter Chua model with cubic nonlinearity is
studied applying numerical continuation and numerical solutions methods.
Regarding numerical solution methods, its dynamics is characterized on Lyapunov
and isoperiodic diagrams and regarding numerical continuation method, the
bifurcation curves are obtained. Combining both methods the bifurcation
structures of the model were obtained with the possibility to describe the {\it
shrimp}-shaped domains and their endoskeletons. We study the effect of a
parameter that controls the dimension of the system leading the model to
present transient chaos with its corresponding basin of attraction being
riddled.Comment: 9 figures, to appear in PL
VSR symmetries in the DKP algebra: the interplay between Dirac and Elko spinor fields
VSR symmetries are here naturally incorporated in the DKP algebra on the
spin-0 and the spin-1 DKP sectors. We show that the Elko (dark) spinor fields
structure plays an essential role on accomplishing this aim, unravelling hidden
symmetries on the bosonic DKP fields under the action of discrete symmetries.Comment: 17 page
Identifying Causal Effects of Nonbinary, Ordered Treatments using Multiple Instrumental Variables
This paper addresses the challenge of identifying causal effects of
nonbinary, ordered treatments with multiple binary instruments. Next to
presenting novel insights into the widely-applied two-stage least squares
estimand, I show that a weighted average of local average treatment effects for
combined complier populations is identified under the limited monotonicity
assumption. This novel causal parameter has an intuitive interpretation,
offering an appealing alternative to two-stage least squares. I employ recent
advances in causal machine learning for estimation. I further demonstrate how
causal forests can be used to detect local violations of the underlying limited
monotonicity assumption. The methodology is applied to study the impact of
community nurseries on child health outcomes
Hsc66 substrate specificity is directed toward a discrete region of the iron-sulfur cluster template protein IscU
Hsc66 and Hsc20 comprise a specialized chaperone system important for the assembly of iron-sulfur clusters in Escherchia coli. Only a single substrate, the Fe/S template protein IscU, has been identified for the Hsc66/Hsc20 system, but the mechanism by which Hsc66 selectively binds IscU is unknown. We have investigated Hsc66 substrate specificity using phage display and a peptide array of IscU. Screening of a heptameric peptide phage display library revealed that Hsc66 prefers peptides with a centrally located Pro-Pro motif. Using a cellulose-bound peptide array of IscU we determined that Hsc66 interacts specifically with a region (residues 99-103, LPPVK) that is invariant among all IscU family members. A synthetic peptide (ELPPVKIHC) corresponding to IscU residues 98-106 behaves in a similar manner to native IscU, stimulating the ATPase activity of Hsc66 with similar affinity as IscU, preventing Hsc66 suppression of bovine rhodanese aggregation, and interacting with the peptide-binding domain of Hsc66. Unlike native IscU, however, the synthetic peptide is not bound by Hsc20 and does not synergistically stimulate Hsc66 ATPase activity with Hsc20. Our results indicate that Hsc66 and Hsc20 recognize distinct regions of IscU and further suggest that Hsc66 will not bind LPPVK motifs with high affinity in vivo unless they are in the context of native IscU and can be directed to Hsc66 by Hsc20
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