1,718 research outputs found
Uniform semiglobal practical asymptotic stability for non-autonomous cascaded systems and applications
It is due to the modularity of the analysis that results for cascaded systems
have proved their utility in numerous control applications as well as in the
development of general control techniques based on ``adding integrators''.
Nevertheless, the standing assumptions in most of the present literature on
cascaded systems is that, when decoupled, the subsystems constituting the
cascade are uniformly globally asymptotically stable (UGAS). Hence existing
results fail in the more general case when the subsystems are uniformly
semiglobally practically asymptotically stable (USPAS). This situation is often
encountered in control practice, e.g., in control of physical systems with
external perturbations, measurement noise, unmodelled dynamics, etc. This paper
generalizes previous results for cascades by establishing that, under a uniform
boundedness condition, the cascade of two USPAS systems remains USPAS. An
analogous result can be derived for USAS systems in cascade. Furthermore, we
show the utility of our results in the PID control of mechanical systems
considering the dynamics of the DC motors.Comment: 16 pages. Modifications 1st Feb. 2006: additional requirement that
links the parameter-dependency of the lower and upper bounds on the Lyapunov
function, stronger condition of uniform boundedness of solutions,
modification and simplification of the proofs accordingl
Arrhythmogenic right ventricular cardiomyopathy associated with severe left ventricular involvement in a cat.
An 8-year-old, 4 kg, intact female, domestic shorthaired cat was
referred for tachypnea and pleural effusion. A 24-h Holter recording showed
numerous polymorphic ventricular premature complexes with left and right bundle
branch block morphology. Echocardiographic examination revealed right atrial and
ventricular dilation. The right ventricular free wall was thin and aneurysmal. The
cat died 10 days after initiation of antiarrhythmic therapy. Gross and histopathological
findings were consistent with arrhythmogenic right ventricular cardiomyopathy
(ARVC) associated with severe left ventricular involvement
The Genetic and Environmental Effects on Diabetes in Humans and Animals: An Overview
Despite intense scrutiny the precise etiology of diabetes mellitus remains unclear. There appear to be two major forms of diabetes: juvenile-onset or insulin-dependent diabetes, and late-onset or insulin-independent diabetes; the late-onset form, in itself, may be etiologically heterogeneous. Either form may occur at any age, with a clear distinction between the two often being difficult to make. Juvenile-onset diabetes, representing 5% to 10% of all cases, is characterized by abrupt onset, clinical manifestation of hyperglycemia and ketoacidosis, and generally by a requirement for exogenous insulin; in maturity-onset diabetes plasma levels of insulin are usually normal or elevated and the abnormality in glucose metabolism results from a decrease in the number of insulin receptors rather than a deficiency of the hormone itself
Aquaporin 1 (Aqp1) expression in healthy dog tears
Aquaporins (AQPs) are a family of thirteen membrane proteins that play an essential role in
the transport of fluids across the cell plasma membrane. Recently, the expression of AQPs in dierent
ocular tissues and their involvement in the pathophysiology of eye diseases, have garnered attention.
Considering that literature on AQP expression in the lacrimal glands and their secretion is scarce,
we aimed to characterise AQP1 expression in the tears of healthy dogs using two tear collection
methods (Schirmer tear strips (STS) and ophthalmic sponges (OS)). Fifteen healthy dogs, free of
ophthalmic diseases, were included in the study. Tear collection was performed by using STS in one
eye and OS in the other. After the extraction of proteins from the tears, the expression of AQP1 was
analysed by Western blotting. AQP1 was expressed as a band of 28 kDa. In addition, dierences
were observed in the expression of AQP1 and in the correlation between tear volume and protein
concentration, in tears collected by the two dierent methods. Our results suggest that AQP1 has a
specific role in tear secretion; further research is required to assess its particular role in the function of
the ocular surface in eye physiology and pathology
On high-speed turning of a third-generation gamma titanium aluminide
Gamma titanium aluminides are heat-resistant intermetallic alloys predestined to be employed in components suffering from high mechanical stresses and thermal loads. These materials are regarded as difficult to cut, so this makes process adaptation essential in order to obtain high-quality and defect-free surfaces suitable for aerospace and automotive parts. In this paper, an innovative approach for longitudinal external high-speed turning of a third-generation Ti-45Al-8Nb- 0.2C-0.2B gamma titanium aluminide is presented. The experimental campaign has been executed with different process parameters, tool geometries and lubrication conditions. The results are discussed in terms of surface roughness/integrity, chip morphology, cutting forces and tool wear. Experimental evidence showed that, due to the high cutting speed, the high temperatures reached in the shear zone improve chip formation, so a crack-free surface can be obtained. Furthermore, the use of a cryogenic lubrication system has been identified in order to reduce the huge tool wear, which represents the main drawback when machining gamma titanium aluminides under the chosen process condition
Eigenvector Centrality Distribution for Characterization of Protein Allosteric Pathways
Determining the principal energy pathways for allosteric communication in
biomolecules, that occur as a result of thermal motion, remains challenging due
to the intrinsic complexity of the systems involved. Graph theory provides an
approach for making sense of such complexity, where allosteric proteins can be
represented as networks of amino acids. In this work, we establish the
eigenvector centrality metric in terms of the mutual information, as a mean of
elucidating the allosteric mechanism that regulates the enzymatic activity of
proteins. Moreover, we propose a strategy to characterize the range of the
physical interactions that underlie the allosteric process. In particular, the
well known enzyme, imidazol glycerol phosphate synthase (IGPS), is utilized to
test the proposed methodology. The eigenvector centrality measurement
successfully describes the allosteric pathways of IGPS, and allows to pinpoint
key amino acids in terms of their relevance in the momentum transfer process.
The resulting insight can be utilized for refining the control of IGPS
activity, widening the scope for its engineering. Furthermore, we propose a new
centrality metric quantifying the relevance of the surroundings of each
residue. In addition, the proposed technique is validated against experimental
solution NMR measurements yielding fully consistent results. Overall, the
methodologies proposed in the present work constitute a powerful and cost
effective strategy to gain insight on the allosteric mechanism of proteins
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