bluuebunny/crossref_metadata_2025 huggingface dataset:
Supervised learning control of a generic missile
Authors: Jones Campbell
Published: November 2007

This paper makes use of artificial neural networks to perform the control function in the lateral autopilot of a generic missile. The neural autopilot controller is formulated as a three layer, non-linear, discrete time-series neural network whose parameters are adjusted under a supervised learning environment via the Levenberg-Marquardt (LM) optimisation algorithm. As opposed to using heuristic reasoning for selecting the network input and output parameters, a novel technique utilising a priori knowledge of the baseline controller is used. The current fin position command is modelled as a function of the past value of commanded fin position, current and past values of lateral acceleration command, achieved fin position, measured lateral acceleration and body rate.

The necessary training and recall data are obtained from time-histories of missile dynamic response when the autopilot control function is being performed by a baseline controller obtained by solving a discrete optimal Linear Quadratic Regulator (LQR) problem.

Lateral acceleration time histories for two flight speeds for a range of incidences are used to illustrate performances. The neural controller is validated using a test lateral acceleration command sequence which differs significantly from that used for generating the network training data. The effectiveness of the proposed neural controller design can be judged from an examination of these digital simulation response results. The dynamic performance of the neural controller is also compared with that of the baseline LQR controller.
Neural control of an aircraft load alleviation control system
Authors: McLean D.
Published: November 2007

The use of neural network controllers to obtain structural load alleviation of a large transport aircraft which exhibits a significant number of bending modes is novel in aircraft flight control systems. In this paper some details of a mathematical model of the aircraft dynamics which was used in the development of the controllers is presented first. Next, details relating to a linear, continuous optimal LQR controller (the baseline controller) are presented. The results obtained from a digital simulation of the optimal structural load alleviation control system (SLACS) then follow. These results and many others obtained from the same simulation were used as the training data required by the neural network controllers used in the design. Two different types of neural network were considered for use, and information about the corresponding training performance and control effectiveness is also presented. The dynamic performance achieved by using the preferred neural controller is compared with that obtained using the baseline LQR controller. A number of suggestions are made in the conclusions in respect of the choice of type of neural network for use as controllers in a SLACS.
The Method of Referred Derivatives: a new technique for solving implicit equations in dynamic simulation
Authors: Thomas P.J.
Published: November 2007

Stiffness in simulation may be reduced or avoided by using algebraic equations to replace the differential equations describing the parts of the model with very, fast dynamics. However, if the resulting simultaneous equations are nonlinear, an implicit set of equations may arise for which no direct method of solution is possible. This paper sets out a novel method for converting such equations into an equivalent set of linear equations which may be solved for the time-derivatives of the original variables, either explicitly or by Gauss elimination. These derivatives may then be integrated along with the derivatives found in the normal way for the slower system states. A worked example of a flow network is provided to illustrate the robustness and practical significance of the method.
Neural network applications in process modelling and predictive control
Authors: Gomm J.B. , Williams D. , Evans J.T. , Doherty S.K.
Published: November 2007

Neural network techniques are investigated applied to the modelling and control of non-linear processes. The development of process models and predictive controllers using two feed-forward neural networks - the multi-layer perceptron and the radial basis function network - is described. The capabilities of these neural networks are demonstrated in two practical applications to modelling and control of a liquid level rig and a multi- variable in-line pH process. On-line results illustrate the performance of neural network predictive control schemes for set-point tracking over a wide non-linear operating range and regulation in the presence of significant disturbances.
Process tomography - the state of the art
Authors: Beck M.S. , Dyakowski T. , Williams R.A.
Published: November 2007

This review provides an overview of the tomographic sensing methods that can be utilised to study process behaviour and their particular attributes (speed, sensi tivity, robustness, etc.). It provides literature citations and sources of information which potential users may consult. Particular emphasis is placed upon electrical methods, due to their inherent suitability for widespread on-line use. Future possible measurement capabilities of the family of electrical methods are discussed.
Internal valve leakage detection using an acoustic emission measurement system
Authors: Sharif Mohamed A. , Grosvenor Roger I.
Published: November 2007

A detailed experimental study was conducted to determine the lowest detectable compressed air leakage rate through an industrial control valve that can be reliably detected using an acoustic emission (AE) technique. Through-valve leakage was deliberately introduced into a 25.4 mm (1 in.) hard-seat globe type control valve under controlled conditions. This was achieved by carefully adjusting the control signal, 4-20 mA d.c., to the valve positioner which, in turn, varied the clearance between the valve plug and seat. Two AE sensors together with the state-of-the-art data acquisition and processing systems were used to monitor a wide range of leakage rates under different working conditions. The effects of the background noise on the measured AE signal were considerably reduced by using the real-time programmable filters that were part of the AE measurement system. This was carried out to produce more reliable and consistent results. The sensitivity of the AE sensors was improved by using line amplifiers with variable gain. The frequency spectrum analysis of the AE signal indicated that leak-related frequency components can be clearly distinguished from those produced due to background noise. Furthermore, it was evident that the selected leak-related frequency components increased in their amplitude as the leakage rate was increased. The paper concludes by illustrating that AE can be used reliably to detect the onset of air leakage through control valves at a differential pressure that could be as low as 110.3 kPa (1.103 bar) and in a noisy industrial environment.
LQG Feedforward/feedback stochastic optimal control and marine application
Authors: Grimble M.J.
Published: November 2007

The solution of a 31/2 degree-of-freedom H, stochastic optimal control problem is discussed. The system is assumed to be scalar and includes a 21/2 degree-of-freedom tracking controller, together with a feedforward control action. The optimisation is based upon an extended cost-function which allows separate costing of the terms due to the feedback, reference and feedforward controllers. This enables the amount of feedforward action to be varied relative to the feedback action and the robustness of the feedback-loop to be shaped independently of the tracking performance. The use of a separate cost term to be able to vary the amount of feedforward action and the resulting design steps are novel and important in applications. Previous solutions did not allow separate cost tuning of the feedforward control terms, A ship positioning design study, that utilises feedforward action, is presented to illustrate the benefits of the approach.
Evaluating deterministic errors in low - bandwidth digital filters using Taylor series expansions
Authors: Oliver M.A. , Forsythe W.
Published: November 2007

A method is presented to show how deterministic errors in low-bandwidth digital filters may be expressed in terms of the input signal and its derivatives. By applying a Taylor series expansion to the delayed terms of the difference equation implemented by the digital filter, the difference equation may be written as a differential equation which allows easy computation of the deterministic errors, The paper also demonstrates the importance of performing error analysis as part of the digital filter design process.
Modelling the controller of a process
Authors: Holinagel Erik
Published: November 2007

Models of humans (operators, controllers) in human-machine systems have tacitly assumed that humans must have a model of the process in order to control it. Humans have therefore traditionally been described as information processing systems with an internal or mental model of the process as an important component. A more systemic or cybernetic view acknowledges that the human must be a model of the process in order to control it. This suggests a different approach to modelling, which is functional rather than structural, and where the emphasis is on how thejoint human-machine system can maintain control of a situation. A specific model, called the Contextual Control Model (COCOM), which is based on the principles of cognitive systems engineering, illustrates the approcach, COCOM provides a foundation for analysing controller performance as well as implementing controller needs.
The acquisition of preposition stranding by second language learners and parametric variation
Authors: van Buren Paul , Smith Michael Sharwood
Published: November 2007

This paper discusses the application of Government Binding Theory to second language acquisition in the context of a project which is looking into the acquisition of preposition stranding in English and Dutch. The bulk of the discussion focuses on the theoretical problems involved. Firstly, the potential value of Government Binding Theory in principle is considered both in terms of the formulation of linguistic questions per se and also in terms of more specifically acquisitional questions having to do with the speed and order of acquisition. Secondly, some results in the pilot studies conducted so far in Utrecht are examined with respect to the theoretical usefulness of the framework adopted. The potential of the framework to generate sophisticated linguistic research questions is found to be undeniable. The acquisitional aspects need to be elaborated and adapted to cope with the special features of second, as opposed to first, language acquisition. This involves an elaboration of scenarios to be investigated: one in which the learner's initial assumption is that the unmarked setting of a given parameter of Universal Grammar holds for the target system, one in which the settings of parameters shared by the target and native systems are assumed to be identical, the second being a 'cross linguistic' scenario. These possibilities are considered in the light of the nature of evidence derived from the input and in the light of a set of possible learning strategies derived from the scenarios. The scenarios, the types of evidence and the strategies are spelled out in terms of the specific problem of preposition stranding in Universal Grammar, in Dutch and in English.
The accessibility of Universal Grammar in adult language learning
Authors: Bley-Vroman Robert W. , Felix Sascha W. , loup Georgette L.
Published: November 2007

This paper investigates whether Universal Grammar (UG) is accessible to adult language learners. If adult acquirers have consistent access to intuitions of grammaticality in cases where the relevant constraints are underdetermined by the native language, this suggests that Universal Grammar continues to function in adult acquisition.

Advanced Korean adult acquirers of English were given a test of grammaticality judgements on English wh-movement sentences, where the relevant constraints are thought to derive from principles of UG. Since Korean does not have syntactic wh-movement, correct intuitions cannot derive from native language transfer. Analysis of the results and comparison with native speaker results suggests a complex picture of the function of UG in adult language acquisition; however, clear UG effects were found.
The UG paradox in L2 acquisition
Authors: Clahsen Harald , Muysken Pieter
Published: November 2007

There is a considerable amount of recent evidence that stable principles of Universal Grammar (UG) are available to adult second language (L2) learners in structuring their intuitions about the target language grammar. In contrast, however, there is also evidence from the acquisition of word order, agreement and negation in German that there are substantial differences between first language (L1) and L2 learners. In our view, these differences are due to UG principles guiding L1, but not L2 acquisition. We will show that alternative ways of accounting for the L1/L2 differences are not successful. Finally we will deal with the question of how our view can be reconciled with the idea that L2 learners can use UG principles to some extent in the evaluation of target sentences.
Parameters in L2 learning: Flynn revisited
Authors: Eubank Lynn
Published: November 2007

In a series of studies, Suzanne Flynn (1984; 1987a; 1987b) has proposed a specific theory with regard to Universal Grammar (Chomsky, 1986) and second language learning. The present study, a replication of the methodology and hypotheses in Flynn (1987b), utilizes Arabic-speaking learners of ESL, who are predicted by Flynn's theory to perform much like her Spanish-speaking subjects. Present findings, however, contradict those of Flynn's work and, thus, cast doubt on her theory of Universal Grammar and L2 learning. Closer examination then reveals that the linguistic underpinnings of Flynn's theory in Huang (1982) have been superseded by the more recent analysis of Koopman (1984), which does not support Flynn's theory. Furthermore, certain assumptions on processing main and subordinate clauses (Townsend and Bever, 1978) and sentence anaphora (Carden, 1986; Reinhart, 1986), which have the capacity to predict Flynn's findings, also fail satisfactorily to predict the results from the speakers of Arabic. Finally, an analysis that predicts a failure of parsing under certain conditions is presented and found to predict the present findings with a high degree of accuracy. However, the parsing analysis must be subjected to further study with an aim toward falsification before it can be assumed to be conclusive.
Field dependence-independence and hemisphericity as variables in L2 achievement
Authors: Alptekin Cem , Atakan Semiha
Published: November 2007

Following an extensive review of the literature, this study explores the relationship between L2 achievement and two learner characteristics - field dependence-independence and hemisphericity. Sixty-nine Turkish students of 11 to 12 years of age in an intensive EFL programme were administered the GEFT, the CLEM, and tests of L2 achievement. Significant positive correlations were observed between the GEFT scores and scores on L2 achievement tests. As expected, field independent learners performed better on the discrete-point and cloze tests. Hemisphericity, however, was not found to be related to L2 achievement. These results are evaluated critically and their implications for further research are discussed.
Longitudinal L2-attrition versus L2-acquisition, in three Turkish children- empirical findings
Authors: Kuhberg Heinz
Published: November 2007

The attrition of German in two Turkish girls (seven and nine years old), previously resident in Germany, was observed in Turkey. The attrition was compared to the L2-acquisition of German of a Turkish boy aged 11. Attrition did not set in immediately. In the second stage, after six months, slower speech, hesitation and free morpheme code-switching to Turkish due to lexical attrition, particularly in verbs, indicated its onset. Basic grammatic al categories were involved in the third stage. Bound morpheme code- switching became the predominant pattern. Basic syntactic patterns of German were retained longest. Attrition was largely a mirror-image of acquisition. Simplification, overgeneralization and over-regularization were strikingly similar in both sets of data. Code-switching turned out to be developmentally systematic, and even 'grammaticalized' in the final stages.
Variation linguistics and SLA
Authors: Preston Dennis R.
Published: November 2007

Sociolinguistics (here called variationist linguistics) has been misunderstood and misrepresented in second language acquistion (SLA) research. In spite of that, several productive studies (many of which use the VARBRUL statistical program) have made significant contributions to our understandings of variation in SLA data, contributions which touch on the linguistic and not the social concerns of such data. The failure of SLA researchers who belong to the so-called 'dominant paradigm' (or Chomskyan or Universal Grammar (UG) research programme) to realize that belief in a so-called variable competence is not a prerequisite to variation studies has been particularly harmful. On the other hand, the failure of sociolinguists to take psycholinguistic matters seriously has been another serious drawback to interfield co-operation; a summary of a plausible variationist psycholinguistics (within an SLA setting and allowing UG interpretation) is provided.
Sentence matching and processing in L2 development
Authors: Eubank Lynn
Published: November 2007

The processing strategies described in Clahsen (1984) to explain the develop ment of German word order make predictions that can be tested ex perimentally. Clahsen's Initialization/Finalization Strategy (IFS) in particular predicts that uninverted, ADV-SVO sentences will exact less cost in terms of processing than inverted, ADV-VSO sentences, even though inverted sent ences are grammatical in the target language and uninverted sentences are ungrammatical. The experimental means employed to test this prediction is the Sentence Matching (SM) procedure described originally in Freedman and Forster (1985). In the SM procedure, response times are elicited for particular types of sentences by measuring the time (in msec.) it takes for subjects to determine whether two sentences presented by computer are identical or different.

The results of one of the experiments reported here show that inverted sentences result in significantly shorter response times than uninverted sentences for non-native speakers. This finding directly contradicts the IFS-derived prediction. However, further experimental work reported here indicates that native speakers do not respond at all to the inverted-uninverted contrast. The rest of the article thus seeks to explain this somewhat surprising finding. The proposed explanation also suggests that natives and non-natives may process sentences in the SM task in rather different ways.
Retention of foreign vocabulary learned using the keyword method: a ten-year follow-up
Authors: Beaton Alan , Gruneberg Michael , Ellis Nick
Published: November 2007

This article assesses one individual's level of recall for foreign vocabulary learned ten years previously using the keyword method. Without any revision at all, he remembered 35% of the test words with spelling fully correct and over 50% with only very minor errors of spelling. After 10 minutes spent looking at a vocabulary list, recall increased to 65% and 76% respectively. After a period of revision lasting a further 1½ hours, recall was virtually 100%. This level of recall was maintained for at least one month. The results indicate 1) that the keyword method (as incorporated in Linkword courses) may be used to learn a large list of vocabulary; and 2) this method of learning is not inimical to retention in the long term. Some theoretical aspects of the findings are discussed.
Text-based tasks and incidental vocabulary learning
Authors: Joe Angela
Published: November 2007

This case study investigates the vocabulary knowledge gains made by an L2 adult learner of English as a result of performing a read and retell task. The learner participated in a vocabulary knowledge interview, followed by a read and retell task. An oral protocol was taken from the retelling component of the task. Subsequently, a second vocabulary knowledge interview and two multiple-choice tests were completed. The effects of three learning conditions (attention, retrieval and generation) which can facilitate vocabulary learning from text-based tasks are discussed. Attending to the various components of a word and retrieving a to-be-learnt word in a text-based task facilitate the acquisition of unfamiliar words. More importantly, the quality of vocabulary use, or a higher level of generation, appears to have had a more powerful effect on vocabulary acquisition.
L2 cognitive states and the Full Transfer/Full Access model
Authors: Schwartz Bonnie D. , Sprouse Rex A.
Published: November 2007

This article is a defence of the Full Transfer/Full Access (FT/FA) model. FT/FA hypothesizes that the initial state of L2 acquisition is the final state of L1 acquisition (Full Transfer) and that failure to assign a representation to input data will force subsequent restructurings, drawing from options of UG (Full Access). We illustrate the FT/FA model by reviewing our analysis of the developmental Turkish-German Interlanguage data of Schwartz and Sprouse (1994) and then turn to other data that similarly receive straightforward accounts under FT/FA.

We also consider two other competing hypotheses, both of which accept Full Access but not Full Transfer: the Minimal Trees hypothesis (no transfer of functional categories) of Vainikka and Young-Scholten (1994; 1996) and the Weak Transfer hypothesis (no transfer of the values associated with functional categories) of Eubank (1993/94). We provide an example of (extremely robust) L2 acquisition data that highlight the inadequacy of the Minimal Trees hypothesis in regard to stages of Interlanguage subsequent to the L2 initial state. As for Weak Transfer, we show that the morphosyntactic empirical foundations which drive the entire approach are flawed; hence the Weak Transfer hypothesis remains without motivation.

Finally, we consider several conceptual issues relating to transfer. These all argue that the FT/FA model provides the most coherent picture of the L2 initial cognitive state. In short, FT/FA embodies the most suitable programme for understanding comparative Interlanguage development.
On the primacy of theory in applied studies: a critique of Pienemann and Johnston (1987)
Authors: Mellow J. Dean
Published: November 2007

This article critiques Pienemann and Johnston (1987), an influential model of the acquisition of ESL morphology. While Pienemann and Johnston claimed that their model is confirmed and supported by the generative approach to morphology developed in Selkirk (1982), this article indicates that Selkirk's lexicalist theory actually opposes their proposals. In addition, this article demonstrates that their proposals are incompatible with syntactic analyses of word formation. The widespread influence of the Pienemann and Johnston model suggests that L2 researchers must ensure that models of SLA are solidly grounded in foundational theories.
The cardiopulmonary bypass pump-priming fluid and nitrogen balance after open-heart surgery in adults
Authors: McKnight CK , Elliott MJ , Holden MP , Pearson DT
Published: November 2007

Different crystalloid cardiopulmonary bypass pump-priming fluids provide very different substrate loads to patients undergoing open-heart surgery. As a result they may modulate the endocrine milieu, and thus might be expected to alter postoperative nitrogen balance. To test this hypothesis, 24 adult patients undergoing open-heart valve surgery were randomized into four matched groups each to receive a different prime, namely: Hartmann's solution, Plasmalyte 148R, Solution 11 R and a prime consisting of equal volumes of Hartmann's solution and 5% dextrose. Accurate nitrogen balance studies were obtained each 24 hours from one day preoperatively to seven days postoperatively.

The results obtained demonstrated that postoperative nitrogen balance was unaffected by the nature of the crystalloid pump prime. Nitrogen balance in the patients studied was better than that reported from other centres in similar patients.
Complement activation by different cardiopulmonary bypass priming solutions
Authors: Gaspardone Achille , Ciavolella Massimo , Mercogliano Domenico , Marino Benedetto , Chiariello Luigi , Carlizzi Guglielmo
Published: November 2007

Similarities between the known biological activities of complement derived factors and the clinical findings observed in the 'post-pump syndrome' suggest that complement may play a role in the pathogenesis of this syndrome.

Mixing of blood with autologous or homologous blood revealed no significant reduction in C3 and C4 concentration, whereas mixing with plasma showed a lower C3 value without differences in C4. Mixing of blood with albumin, Normosol, D5 water and normal saline solution revealed a progressive reduction both in C3 and C4 concentration; mixing with Emagel showed C4 reduction, without reduction in C3 concentration.

Our findings suggest that crystalloid solutions used for priming the pump oxygenator circuit are an additional C3 and C4 activating factor. Such activation should be regarded as a 'pre-pump complement activation'.
In vitro plasma nifedipine concentration during heart-lung machine function
Authors: Noera G. , Massini C. , Baggio G.
Published: November 2007

The use of calcium antagonists such as nifedipine for myocardial protection during cardiac surgery has been advocated by several authors. During extracorporeal circulation many factors, such as light, interaction with circuit materials and haematocrit, may contribute to decrease plasma clearance of calcium antagonists

In an in vitro model of a heart-lung machine, plasma nifedipine and prime concentrations were detected with a series of samples at different temperatures (25 °C and 37 °C), haematocrits (0%, 20%, 30% and 40%) and light conditions (light and dark).

The results show a rapid drop of nifedipine concentration with a halflife of about 3-9 minutes and this situation is influenced with statistical significance by the presence of light and increased haematocrit.

The knowledge of this condition is useful when nifedipine is used before/ during cardiopulmonary bypass and during cardioplegia and reperfusion infusion with the use of extracorporeal devices.
A techniaue of anaesthesia and surgery for the implantation of ventricular assist devices in sheep
Authors: Macrae Duncan , Glenville Brian
Published: November 2007

A technique of anaesthesia and surgery used in sheep, during insertion of ventricular asssist devices is described. Some animals also underwent double- reservoir cardiopulmonary bypass. Reference is made to previous reports of such techniques in sheep.
Paediatric extracorporeal priming procedures: does low temperature priming promote histamine release?
Authors: Marath A. , Man W. , Taylor KM
Published: November 2007

We have recently reported pathologically elevated plasma histamine levels in adult patients undergoing cardiac surgery throughout the perioperative period. We have found markedly higher histamine levels in paediatric practice. The priming volume of the smallest extracorporeal systems is invariably greater than the circulating blood volume of neonates and infants, necessitating the use of stored donor blood in the initial priming procedure. In 40 paediatric cases, arbitrarily selected, sampling from the arterial port of the oxygenator prior to the initiation of bypass revealed massively elevated plasma histamine levels (>30ng/ml) in those extracorporeal circuits in which the priming volume was smallest and the priming temperature lowest - at 10-12°C. It is clear that the use of donor blood (in this series less than five days old) may contribute to the delivery of histamine into the paediatric patient's circulation at the onset of cardiopulmonary bypass and that the priming temperature may play a role.
Factors affecting the pulsatile hydraulic power output of the Stockert roller pump
Authors: Wright Gordon
Published: November 2007

A detailed assessment of the hydraulic power output of the Stockert roller pump was performed with the pump operating in its 'pulsatile' mode. Pressure and flow waveforms and the pulsatile power generated in a model of the human vascular bed were dependant upon the pump output, the pump control settings and the diameters of the arterial line, the pump insert and aortic cannula. The pulsatile power output was lower when a silicone rubber pump insert was used rather than a polyvinyl chloride insert. The incorporation of a Cobe CML flat-sheet membrane oxygenator into the arterial line reduced the pulsatile power to levels similar to those obtained with the pump operating in its 'continuous' mode. Incorporating a Sarns hollow fibre membrane oxygenator or a Pall extracorporeal blood filter had less effect and variations in perfusate viscosity or the length of the arterial line did not appear to have any effect. It seems probable that the experimental and clinical effects of 'pulsatile' flow during cardiopulmonary bypass with this pump will be highly dependant upon the operating conditions.
Ultrastructural study comparing the myocardial protective effects of four different infusates (Bretschneider's, St Thomas's, standard Ringer's and blood potassium solutions) in the human heart
Authors: Baudet E. , Laborde N. , Roques X. , Berty A. , Oca C. , Le Menn R.
Published: November 2007

Comparative mitochondrial ultrastructural changes during myocardial ischaemic periods have been assessed when using four different solutions: Bretschneider's solution (BS) (K+ = 10 mEq/l) at 4°C; St Thomas's hospital solution (STS) (K+ = 20 mEq/l) at 4°C; standard Ringer's solution (SRS) (K+ = 2.7 mEq/l) at 4°C; blood potassium cardioplegic solution (BPS) (K+ = 21 mEq/l) at 15°C.

BS (n = 8), STS (n = 10), SRS (n = 8) and BPS (n = 8) were infused in 34 patients undergoing aortic valve replacement (n = 17) or aortocoronary bypass grafting (n = 17), after aortic crossclamping, either in the aorta or in both coronary ostia, until the septal myocardial temperature reached 10-13°C for crystalloid solutions or 15°C for blood cardioplegia. Myocardial biopsies were taken from the left ventricular apex, on a beating heart, at the beginning and end of bypass.

To assess the degree of ischaemic injury, an ultrastructural evaluation of the mitochondria was done and four histological classes have been defined: class I- dense matrix and cristae; class II — occasional mitochondrial swelling; class III — decrease in matrix density with extensive swelling; class IV — severe swelling and/or rupture of matrix.

This study showed that: (1) only the St Thomas's and Bretschneider's solutions provide a rapid electromechanical asystole; (2) isolated hypothermic crystalloid solution with low potassium concentration (standard Ringer) is not sufficient either to induce cardiac arrest or to prevent detrimental mitochondrial changes; (3) Bretschneider's solution appears to provide the best ultrastructural mitochondrial preservation during myocardial ischaemia.
Biomedical engineering management of Novacor left Ventricular assist system (LVAS) patients
Authors: Pristas John M , Borovetz Harvey S , Kormos Robert L , Griffith Bartley P
Published: November 2007

As the number of cardiac transplant centres increases, there is an associated decrease in the availability of donor organs per centre. Subsequently, hospitals are utilizing cardiac assist systems (total artificial heart and ventricular assist devices) as a bridge to cardiac transplantation. Because of the engineering complexities related to the clinical implantation and follow up of these devices, a successful centre should have a well co-ordinated biomedical engineering programme. These engineers are responsible for the calibration, monitoring, and continued operation of these units. This paper is intended to serve as a guide to any centre interested in utilizing total artificial heart and ventricular assist systems, in particular the Novacor left ventricular assist system, and focuses on the management and function of the biomedical engineering component of our cardiac assist programme.
The use of cardiopulmonary bypass with profound hypothermia and circulatory arrest during the surgical treatment of giant intracranial aneurysms
Authors: Drakley SK , Fisher AR , O'Riordan JB , Sharr M.
Published: November 2007

The surgical treatment of giant intracranial aneurysms can be aided by using cardiopulmonary bypass to provide hypotension under hypothermic conditions. Cardiopulmonary techniques need to be modified to deal with the problems that arise during this type of neurosurgery.
Vasomotor waves of arterial blood pressure after cessation of cardiopulmonary bypass in man
Authors: Vainionpää V. , Hollme'n A. , Timisjärvi J.
Published: November 2007

The occurrence of vasomotor waves during cardiopulmonary bypass (CPB) is a recognized phenomenon. The lesser known oscillation of arterial pressure after cessation of CPB was observed in 18 open-heart patients. The duration of an oscillatory wave was 13.5±5.0 seconds, the amplitude 6.1 ±2.6mmNg and the mean arterial pressure 76.5± 10.7mmHg. Inter-and also intraindividual variations in frequency and amplitude of the oscillation, however, did occur. In 13 patients, this oscillation occurred during ventricular epicardial pacing. The oscillation continued until the end of the operation in eight patients; in others, the oscillation was of shorter duration. An oscillation of pulmonary arterial pressure (PAP) was simultaneously observed in nine patients (eight with pacemaker) and central venous pressure (CVP) oscillation in eight patients (all with pacemaker). The duration of a wave was the same as in systemic arterial pressure and the amplitudes were 1.5-3.0mmHg in PAP and 1.0-2.0mmHg in CVP. These arterial vasomotor waves, seen here after CPB, largely resemble those observed during perfusion in man and also the Mayerwaves explored in experimental animals. The pacing rhythm seems to favourthe appearance of those blood pressure oscillations.
Clinical experience of copulsation with PAD via left ventricular apex
Authors: Noera G. , Lodi R. , Pensa PM , Guelfi P. , Biagi B. , Carbone C.
Published: November 2007

Copulsation was performed with a pulsatile assist device (PAD) via the left ventricular apex in two patients who could not be weaned from cardiopulmonary bypass and IABP support after open-heart surgery. In one case an essential improvement of cardiac status was achieved while in the second case the mechanical support was unsuccessful. Clinical data suggest that this technique may have potential in promoting the recovery of ischaemic myocardium but problems related to the type of cannula used and the site of intraventricular location need further investigation.
The influence of pulsatile and nonpulsatile extracorporeal circulation on fluid retention following coronary artery bypass grafting
Authors: Thompson T. , Minami K. , Dramburg W. , Vyska K. , Koerfer R.
Published: November 2007

Thirty male patients undergoing coronary artery bypass grafting were divided into two groups, group receiving pulsatile perfusion, group II nonpulsatile perfusion. A double roller pump system for extracorporeal circulation was employed. Intra- and postoperative fluid balances and bodyweight gains were controlled under clinical conditions. There were no significant differences between the groups with regard to clinical data, operative procedure, perfusion parameters, drug treatment or intensive care treatment. The intra-operative mean fluid balance of group I was 794.0ml (66%) lower than that of group II, while the balance 24 hours postoperatively was 136.7ml (37%) lower in group I. Thus, the total mean fluid balance for the pulsatile group was 931.0ml (59%) lower than the nonpulsatile group, in accordance with the bodyweights, which showed a 954.0g (63%) lower outcome in the pulsatile group. Less supplementary volume and higher urine production were the main factors. It appears that volume saved during pulsatile ECC need not be replaced postoperatively. These findings indicate that pulsatile perfusion leads to diminished fluid overloading, which could be an important advantage, especially for high-risk patients.
High-flow femoro-femoral bypass utilizing small cannulae and a centrifugal pump on the venous side
Authors: McCusker K. , Hoffman D. , Maldarelli W. , Toplitz S. , Sisto D.
Published: November 2007

Femoro-femoral bypass is an established technique in the armamentarium of cardiac surgeons, but poor venous drainage usually restricts the flow rate that can be achieved. We describe a technique whereby full flow (> 2.41 I/min/m2 femoro-femoral bypass) can be achieved with a 17 F arterial and a single 21 F venous cannula placed percutaneously or via a cut-down.

Transoesophageal echo is used to position the tip of the venous cannula accurately in the right atrium. The circuit includes a centrifugal pump on the venous side, pumping into a reservoir; a conventional roller pump delivers blood through the arterial cannula. A parallel arrangement allows the centrifugal pump to be excluded from the circuit at any stage. The system allows flow rates over 2.4 l/min/m 2 despite the size of the venous cannula ; without the centrifugal pump working maximal flow rates are under 1.5 l/min/m2. The right side of the heart is totally decompressed and there is no need to add volume or vasopressors to maintain the desired full flow rate. Once the chest is open, perfusion may continue as before or gravity drainage can be utilized after stopping the centrifugal pump; venous return may be augmented by placing additional cannulae. If desired, slowing drainage by the centrifugal pump temporarily permits the blind placement of a coronary sinus cannula without entraining air. To avoid inadvertent bolus doses with unpredictable effects while the centrifugal pump is running, no drugs should be administered into the right atrium and all infusions into the neck lines must be through flow-regulating pumps. We have found this system useful for (1) hazardous re-operations, (2) pericardiectomy and (3) emergency bypass, when percutaneous cannulation can be used.
The proposed use of a 'screening test' to assess oxygenator performance
Authors: Fried David W , Wilgus Michael A , Weiss Steven J
Published: November 2007

This study aimed to assess whether the use of the physiological shunt equation could (within the first five minutes of initiating CPB) serve as a 'screen' to differentiate normal and dysfunctional oxygenator performance. If dysfunction severe enough to require replacement was necessary, the normothermic patient could be weaned from CPB and replacement would be carried out under safe, controlled conditions. This technique would require postponing the induction of hypothermia (if used), aortic cross-clamping, and arresting the heart until after this screen was completed. This study demonstrates that a strong negative correlation exists between the degree of blood shunting and the membrane's O2 transfer performance (r = -0.874). This relation enables us to predict O 2 transfer performance when only the shunt fraction is known. Of the 41 oxygenators used in this study, 40 demonstrated normal, or below-normal, shunt fractions. Oxygen transfer performance at or above predicted levels would be anticipated for these oxygenators. One of the 41 oxygenators had mildly elevated shunt fractions, which we predicted would be associated with mild O2 transfer dysfunction. Based on the performance screen worksheet we created, replacement was not necessary since the oxygenator maintained high levels of O2 transfer in reserve despite its marginal performance dysfunction.

Assessment of oxygenator performance dysfunction in this earliest phase of CPB would greatly reduce the incidence of emergency oxygenator replacement secondary to actual or perceived oxygenator failure later in the course of the procedure.
Anaesthesia and cardiopulmonary bypass: a UK and Ireland survey
Authors: Patey R. , Alston RP
Published: November 2007

A postal survey of consultant anaesthetists in the UK and Ireland was undertaken in the summer of 1989 to determine anaesthetic practice during cardiopulmonary bypass (CPB). A questionnaire requiring details of anaesthetic agents used for induction of anaesthesia, maintenance of anaesthesia before CPB and during CPB was sent to 198 consultants. There was a 52% response rate. Intravenous anaesthetics were used during induction of anaesthesia, maintenance of anaes thesia and during CPB by 100%, 64% and 81 % of respondents respectively. Opioids were used by 96%, 96% and 80%, volatile anaesthetics by 73%, 95% and 36%, and neuromuscular blockers by 100%, 97% and 90%. It is concluded that a balanced anaesthetic technique using neuromuscular blockers, opioids and intravenous anaesthetics is that which is most commonly used during CPB.
Proportioned blood cardioplegia delivery systems- are you del iveri ng the [K+] you expect?
Authors: Fried David W , Mohamed Hasratt
Published: November 2007

This study was conducted to compare the actual potassium concentration [K+] delivered from a standard 4:1 ratio blood cardioplegia solution with the predicted [K+]. We found that the delivered [K+] ranged from 18.15 to 21.2 mEq/I although we predicted 22.0 mEq/I from our mathematical model. The factors that contributed to this difference were investigated. The ratio of blood:crystalloid was determined by: (1) potassium dilution technique; (2) volume output technique; and (3) from the manufacturer's tubing specifications and tolerances. This resulted in blood:crystalloid ratios of 3.86:1 (3.35-4.49:1), 3.74:1, and 4.0:1 (3.47-4.68:1), respectively. Analysis of the crystalloid component revealed an average [K+] of 75.7 mEq/I (70.0-81.5 mEq/I). Patient [K+] during the study ranged from 4.3 to 6.4 mEq/l. When the effect of clinical extremes in ratio, crystalloid [K+], and patient [K+] were considered, a range of cardioplegia [K+] of 16.0-24.3 mEq/I would be predicted. It was concluded that the ability to control the delivered [K+] with any precision is limited. Manufacturers should (1) match the tubing in such a way as to minimize ratio extremes and (2) adopt a tubing tolerance of ± 0.003 inches. Perfusionists should (1) analyse the crystalloid solution prior to cardiopulmonary bypass (CPB) and (2) analyse the cardioplegia [K+] when there is difficulty arresting the heart or if the patient [K+] is excessively elevated.
Autologous plateletpheresis in cardiac surgery
Authors: Varga Zsolt A
Published: November 2007

Despite remarkable improvement of surgical and cardiopulmonary bypass technique, nonsurgical bleeding is still a serious complication following cardiac surgery. As nonthrombotic material or an ideal anticoagulant preventing contact activation of the blood has not been found, a method to reduce'whole body inflammatory response' and postoperative bleeding is an appealing option to improve the postoperative status of patients undergoing cardiac surgery. Discussing the rationale behind preoperative leucocyte-plasmapheresis the possible benefits of this new method are explained. Reviewing the literature, possibilities of future development is outlined.
Lipid peroxidation in open-heart surgery
Authors: Valen Guro , Khoschsorur Gholam A , Almdahl Sven M , Esterbauer Hermann , Vaage Jarle
Published: November 2007

Production of oxygen free radicals and subsequent lipid peroxidation are thought to occur during cardiopulmonary bypass (CPB) and myocardial ischaemia- reperfusion injury. Malondialdehyde (MDA), a lipid peroxidation product, was measured simultaneously in arterial and coronary sinus blood before CPB and after release of the aortic crossclamp. Additional arterial samples were drawn pre-, per-, and postoperatively. Thirteen patients scheduled for coronary artery and/or valvular surgery were studied. Cold, crystalloid, cardioplegic arrest (54 [35-120] minutes, median [range]) was induced retrogradely. Preoperatively, arterial MDA was 0.78 ± 0.4 (mean ± SD) μmol/l, and increased during CPB (highest level 3.66 ± 1.08 μmol/l, p < 0.002, 30 minutes after the start of reperfusion). Arterial MDA was still increased four hours after the end of CPB (3.17 ± 0.88 μmol/l, p < 0.003), but had returned to normal the first postoperative day. No difference was found between arterial and coronary sinus samples at any time. In conclusion, MDA increased in arterial blood during CPB, indicating that lipid peroxidation occurred. There was no intracoronary release of MDA during reperfusion of the ischaemic heart.
Lipoproteins in heart disease
Authors: Basile-Borgia Annette , Abel John H
Published: November 2007

Most lipids are carried in the circulation by lipoproteins. Liproproteins and their associated proteins, called apolipoproteins, are currently being studied in an effort to further our understanding of atherosclerotic cardiovascular disease. Lipoprotein assembly, secretion, transportation, modification and clearance are essential elements of healthy lipid metabolism. When one or more of these key steps becomes altered, various disease states are induced. Current data suggest that lipoprotein(a), a low density lipoprotein (LDL)-like particle, is an acute phase reactant that plays a critical role in the modulation of fibrinolysis. Several aspects of lipoproteins and lipoprotein metabolism will be examined. Emphasis will be placed on the proatherogenic and thrombogenic effects of oxidized LDL.
Effects of modified constraint-induced movement therapy on reach-to-grasp movements and functional performance after chronic stroke: a randomized controlled study
Authors: Lin K.-C. , Wu C.-Y. , Wei T.-H. , Gung Chang , Lee C.-Y. , Liu J.-S.
Published: November 2007

Objective: To evaluate changes in (1) motor control characteristics of the hemiparetic hand during the performance of a functional reach-to-grasp task and (2) functional performance of daily activities in patients with stroke treated with modified constraint-induced movement therapy.

Design: Two-group randomized controlled trial with pretreatment and posttreatment measures.

Setting: Rehabilitation clinics.

Subjects: Thirty-two chronic stroke patients (21 men, 11 women; mean age=57.9 years, range=43—81 years) 13—26 months (mean 16.3 months) after onset of a first-ever cerebrovascular accident.

Intervention: Thirty-two patients were randomized to receive modified constraint-induced movement therapy (restraint of the unaffected limb combined with intensive training of the affected limb) or traditional rehabilitation for three weeks.

Main measures: Kinematic analysis was used to assess motor control characteristics as patients reached to grasp a beverage can. Functional outcomes were evaluated using the Motor Activity Log and Functional Independence Measure.

Results: There were moderate and significant effects of modified constraint-induced movement therapy on some aspects of motor control of reach-to-grasp and on functional ability. The modified constraint-induced movement therapy group preplanned reaching and grasping (P=0.018) more efficiently and depended more on the feedforward control of reaching (P=0.046) than did the traditional rehabilitation group. The modified constraint-induced movement therapy group also showed significantly improved functional performance on the Motor Activity Log (P<0.0001) and the Functional Independence Measure (P=0.016).

Conclusions: In addition to improving functional use of the affected arm and daily functioning, modified constraint-induced movement therapy improved motor control strategy during goal-directed reaching, a possible mechanism for the improved movement performance of stroke patients undergoing this therapy.