196,157 research outputs found
Dickens and the Pickwick Papers. Unstable Signs in a Transmodal Discourse
No full textThe paper, devoted to Dickens' narrative modes with special reference to "The Pickwick Papers", participates in the larger critical discourse posed by the volume about Literary Turning Points. The focus here is especially on The Pickwick Papers as a trasmodal narrative, inter-playing on words and images, coping with historical transformations as well as genre-adaptations
Proportional electro-hydraulic valves: from analogue to digital control
No full textProportional electro-hydraulic valves are ubiquitous as flow actuators in hydraulic systems. Flow regulation is the result of the accurate positioning of a spool driven by a solenoid and a position sensor, usually a Linear Variable Differential Transformer. The overall control consists of two hierarchical loops: the inner loop is the solenoid current regulator with a closed-loop bandwidth close to 1 kHz. A model-based digital regulator of this kind has been presented elsewhere: requirements and performance are here reminded. The outer loop is a position tracking control, in charge of an accurate positioning of the spool with respect to the valve openings. The paper addresses the outer loop and concentrates on the conversion of an existing industrial analogue controller into a digital one. The analogue controller is a nonlinear proportional, integrative and derivative controller including a second-order derivative, and is capable of recovering a dead-band hysteresis. The digital conversion provides the necessary position derivatives through a state predictor, in order to withstand the 5-kHz Nyquist limit of the power supplier. As such it departs from traditional conversions dating back to more than ten years ago. The digital control law is fed by the state predictions and repeats the analogue control law with some improvements. Preliminary experiments prove that the conversion repeats and improves analogue performance. Some flaws of the resulting digital controller are outlined and discussed in view of a model-based conversion.
Digital current regulator for proportional electro-hydraulic valves featuring unknown disturbance rejection
No full textSolenoid current regulation is well-known and standard in any proportional electro-hydraulic valve. The goal is to provide a wide-band transfer function from the reference to the measured current, thus making the solenoid a fast and ideal force actuator within the limits of the power supplier. The supplier is usually a Pulse Width Modulation (PWM) amplifier fixing the voltage bound and the Nyquist frequency of the regulator. Typical analogue regulators include three main terms: a feedforward channel, a proportional feedback channel and the electromotive force compensation. The latter compensation may be also accomplished by integrative feedback. Here the problem is faced through a model-based design (Embedded Model Control), on the basis of a wide-band embedded model of the solenoid which includes the effect of eddy currents. To this end model parameters must be identified. The embedded model includes a stochastic disturbance dynamics capable of estimating and correcting the electromotive contribution together with the model parametric uncertainty, variability and state dependence. The embedded model which is fed by the measured current and the supplied voltage becomes a state predictor of the controllable and disturbance dynamics. The control law combines a reference generator, state feedback and disturbance rejection to dispatch the PWM with the appropriate duty cycle. Modeling, identification and control design are outlined together with experimental result. Comparison with an existing analogue regulator is also provided
Supplemental material for Relationship between endothelial dysfunction, videocapillaroscopy and circulating CD3+CD31+CXCR4+ lymphocytes in systemic lupus erythematosus without cardiovascular risk factors
No full textSupplemental Material for Relationship between endothelial dysfunction, videocapillaroscopy and circulating CD3+CD31+CXCR4+ lymphocytes in systemic lupus erythematosus without cardiovascular risk factors by I. Cavazzana, S. Piantoni, E. Sciatti, M. Fredi, M. Taraborelli, I. Bonadei, P. Airò, M. Metra, A. Tincani, F. Franceschini and E. Vizzardi in Lupus</p
Leaf-associated bacteria from transgenic white poplar producing resveratrol-like compounds: isolation, molecular characterization and evaluation of oxidative stress tolerance
No full textThe aim of this study was the isolation and characterization of the culturable bacteria inhabiting the leaves of
transgenic white poplars (Populus alba L. ‘Villafranca’) engineered with the StSy gene for the production of resveratrollike
compounds. Resveratrol glucosides are available in small amounts from natural sources or by expensive chemical synthesis
procedures. An alternative approach for the large-scale production of these relevant pharmaceuticals is the use of
transgenic plants as bioreactors, although the occurrence of novel molecules in plants growing under field conditions might
interfere, to some extent, with the associated microbial population. Both epiphytes and endophytes were isolated from the
leaves of 2 StSy transgenic lines producing resveratrol glucosides and from an untransformed plant line grown in a greenhouse.
Eleven isolates were recovered and classified as members of the genus Bacillus by 16S rDNA-based analysis. In
addition, 2 isolates were classified as members of the Curtobacterium and Kocuria genera, respectively. Tolerance to hydrogen
peroxide, UV-C, and paraquat was evaluated, as were the swimming and swarming motility of the leaf-associated
bacteria. Interestingly, the isolates recovered from transgenic tissues showed the ability to withstand oxidative stress compared
with isolates recovered from the untransformed poplar line. In vitro bioassays showed that trans-resveratrol inhibited
both the swarming and swimming motilities in all the tested bacteria. The effects of trans-resveratrol on flagellin production,
required for motility, were also investigated by immunoblot analysis
Evaluation of the expression level of the endogenous marker poUBI gene for studies on transgene stability in bar and StSy GM poplars
No full textDr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
Elastic properties of ascending aorta and ventricular-arterial coupling in women with previous pregnancy complicated by HELLP syndrome
No full textObjective:To compare the elastic properties of the ascending aorta and ventricular-arterial coupling (VAC) in women with a previous pregnancy complicated by hemolysis, elevated liver enzymes, and low platelets (HELLP) syndrome, women who experienced preeclampsia, and healthy controls.Methods:Women with a history of preeclampsia (n = 60) or HELLP syndrome (n = 49) and matched healthy controls (n = 60) underwent transthoracic echocardiography at 6 months to 4 years after delivery. Aortic M-mode and tissue Doppler imaging (TDI) parameters were measured. Aortic diameters were assessed at end-diastole at four levels: Valsalva sinuses, sinotubular junction, tubular tract, and aortic arch. Aortic compliance, distensibility, stiffness index, Peterson's elastic modulus, pulse-wave velocity, and M-mode strain were calculated using standard formulae. Aortic expansion velocity, early and late diastolic retraction velocities, and peak systolic tissue strain (TDI-ε) were determined. VAC was defined as the ratio between aortic elastance (Ea) and left ventricular end-systolic elastance (Ees). All women were free from cardiovascular risk factors.Results:Women with a history of HELLP syndrome showed larger aortas than those with previous preeclampsia or controls, probably related to a higher blood pressure. Aortic elastic properties, including Ea, were similar between HELLP and preeclampsia groups, even comparing cases with early-onset preeclampsia and HELLP. In contrast, Ees was more impaired in the HELLP group than in the other two. Consequently, about one-quarter of women who experienced HELLP syndrome had a pathological VAC, whereas only 5% of previously preeclamptic patients did. Multivariate analysis confirmed the association between HELLP syndrome and VAC, whereas other parameters including aortic compliance, distensibility, stiffness index, and elastic modulus are linked only to gestational age at preeclampsia onset, ad also Ea and Ees did.Conclusions:We found a significant overlap between the aortic elastic properties in women with a history of preeclampsia and those with a previous HELLP syndrome, suggesting a common pathophysiologic pathway. However, women who experienced HELLP syndrome showed a higher blood pressure than other cases and controls, probably determining larger aortas. In addition, VAC was more altered in the HELLP group than in the others because of a higher Ea and a lower Ee
- …
