573 research outputs found
Input-to-state stability of Lur’e systems
An input-to-state stability theory, which subsumes results of circle criterion type, is developed in the context of continuous-time Lur’e systems. The approach developed is inspired by the complexified Aizerman conjecture.</p
An improved method for preparing Agrobacterium cells that simplifies the Arabidopsis transformation protocol
BACKGROUND: The Agrobacterium vacuum (Bechtold et al 1993) and floral-dip (Clough and Bent 1998) are very efficient methods for generating transgenic Arabidopsis plants. These methods allow plant transformation without the need for tissue culture. Large volumes of bacterial cultures grown in liquid media are necessary for both of these transformation methods. This limits the number of transformations that can be done at a given time due to the need for expensive large shakers and limited space on them. Additionally, the bacterial colonies derived from solid media necessary for starting these liquid cultures often fail to grow in such large volumes. Therefore the optimum stage of plant material for transformation is often missed and new plant material needs to be grown. RESULTS: To avoid problems associated with large bacterial liquid cultures, we investigated whether bacteria grown on plates are also suitable for plant transformation. We demonstrate here that bacteria grown on plates can be used with similar efficiency for transforming plants even after one week of storage at 4°C. This makes it much easier to synchronize Agrobacterium and plants for transformation. DNA gel blot analysis was carried out on the T(1 )plants surviving the herbicide selection and demonstrated that the surviving plants are indeed transgenic. CONCLUSION: The simplified method works as efficiently as the previously reported protocols and significantly reduces the workload, cost and time. Additionally, the protocol reduces the risk of large scale contaminations involving GMOs. Most importantly, many more independent transformations per day can be performed using this modified protocol
Die Sauerstoffsättiung als Überwachungsparameter bei Regionalanästhesie mit adjuvanter Sedierung
Standardization of surface electromyography utilized to evaluate patients with dysphagia
<p>Abstract</p> <p>Backgorund</p> <p>Patients suspected of having swallowing disorders, could highly benefit from simple diagnostic screening before being referred to specialist evaluations. We introduce surface electromyography (sEMG) to carry out rapid assessment of such patients and propose suggestions for standardizing sEMGs in order to identify abnormal deglutition.</p> <p>Methods</p> <p>Specifics steps for establishing standards for applying the technique for screening purposes (e.g., evaluation of specific muscles), the requirements for diagnostic sEMG equipment, the sEMG technique itself, and defining the tests suitable for assessing deglutition (e.g., saliva, normal, and excessive swallows and uninterrupted drinking of water) are presented in detail. A previously described normative database for single swallowing and drinking and standard approach to analysis was compared to data on the duration and electric activity of muscles involved in deglutition and with sEMG recordings in order to estimate stages of a swallow.</p> <p>Conclusion</p> <p>SEMG of swallowing is a simple and reliable method for screening and preliminary differentiation among dysphagia and odynophagia of various origins. This noninvasive radiation-free examination has a low level of discomfort, and is simple, timesaving and inexpensive to perform. With standardization of the technique and an established normative database, sEMG can serve as a reliable screening method for optimal patient management.</p
Stability and convergence properties of forced infinite-dimensional discrete-time Lur'e systems
Incremental stability and convergence properties for forced, infinite-dimensional, discrete-time Lur'e systems are addressed. Lur'e systems have a linear and nonlinear component and arise as the feedback interconnection of a linear control system and a static nonlinearity. Discrete-time Lur'e systems arise in, for example, sampled-data control and integro-difference models. We provide conditions, reminiscent of classical absolute stability criteria, which are sufficient for a range of incremental stability properties and input-to-state stability (ISS). Consequences of our results include sufficient conditions for the converging-input converging-state (CICS) property, and convergence to periodic solutions under periodic forcing
Sampled-data integral control of multivariable linear infinite-dimensional systems with input nonlinearities
A low-gain integral controller with anti-windup component is presented for exponentially stable, linear, discrete-time, infinite-dimensional control systems subject to input nonlinearities and external disturbances. We derive a disturbance-to-state stability result which, in particular, guarantees that the tracking error converges to zero in the absence of disturbances. The discrete-time result is then used in the context of sampled-data low-gain integral control of stable well-posed linear infinite-dimensional systems with input nonlinearities. The sampled-date control scheme is applied to two examples (including sampled-data control of a heat equation on a square) which are discussed in some detail
Infinite-dimensional Lur'e systems with almost periodic forcing
We consider forced Lur’e systems in which the linear dynamic component is an infinite-dimensional well-posed system. Numerous physically motivated delay- and partial-differential equa-tions are known to belong to this class of infinite-dimensional systems. We present refinements ofrecent incremental input-to-state stability results [14] and use them to derive convergence results fortrajectories generated by Stepanov almost periodic inputs. In particular, we show that the incrementalstability conditions guarantee that for every Stepanov almost periodic input there exists a unique pairof state and output signals which are almost periodic and Stepanov almost periodic, respectively. Thealmost periods of the state and output signals are shown to be closely related to the almost periodsof the input, and a natural module containment result is established. All state and output signalsgenerated by the same Stepanov almost periodic input approach the almost periodic state and theStepanov almost periodic output in a suitable sense, respectively, as time goes to infinity. The sufficientconditions guaranteeing incremental input-to-state stability and the existence of almost periodic stateand Stepanov almost periodic output signals are reminiscent of the conditions featuring in well-knownabsolute stability criteria such as the complex Aizerman conjecture and the circle criterion
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