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A new stochastic particle transport tool named LAST has been developed to allow seamless integral data assimilation on nuclear reaction model parameters during the evaluation process of nuclear data. The present work demonstrates its capability to perform actuate once-through information propagation from pre-processed application library to integral multiplication factor. Exact perturbation on reactivity is the starting point of the integral feedback on nuclear reaction model parameters. Its implementation in LAST is also shown.

Background and objective: The haemodynamic effects of acute pulmonary hypertension can be largely attributed to ventricular interdependence during diastole. However, there is evidence that the two ventricles also interact during systole. The aim of the present study was to examine the effects of acute pulmonary hypertension on both components of left ventricular systole, i.e. contraction and relaxation, using load-independent indices. Methods: Ten pigs were instrumented with biventricular conductance catheters, a pulmonary artery flow probe and a high-fidelity pulmonary pressure catheter. Haemodynamic measurements were performed in baseline conditions and during stable pulmonary vasoconstriction induced by the thromboxane analogue U46619. Contractility was quantified using the end-systolic pressure-volume and preload recruitable stroke work relationships. The T-end-systolic pressure relationship was used to assess load-dependency of relaxation. Results: Acute pulmonary hypertension caused a decrease in the slope of the left ventricular preload recruitable stroke work relationship (from 6.64 ± 1.7 to 5.19 ± 1.9, mean ± SD; P < 0.05), a rightward shift of the end-systolic pressure-volume relationship (P < 0.05), and an increase in the slope of the T-end-systolic pressure relationship (from -0.15 ± 0.5 to 0.35 ± 0.17; P < 0.05). The diastolic chamber stiffness constant of both ventricles increased during pulmonary hypertension (P < 0.05). Conclusions: In the present model, acute pulmonary hypertension impairs left ventricular contractile function and relaxing properties. The present study provides additional evidence that, besides the well-known diastolic ventricular cross talk, systolic ventricular interaction may play a significant role in the haemodynamic consequences of acute pulmonary hypertension. [ABSTRACT FROM AUTHOR]

Background and objective: Epidural anaesthesia is the preferred technique of anaesthesia for Caesarean section in pre-eclampsia. Spinal anaesthesia is considered by some as a safe and effective alternative, which is especially useful in emergency situations. Combined spinal-epidural anaesthesia, using low doses of local anaesthetics with opioids, is effective and reduces the incidence of hypotension in normal pregnancy. We performed a retrospective chart analysis to evaluate the effects of combined spinal-epidural anaesthesia on maternal haemodynamics and fetal outcome compared to conventional epidural anaesthesia. Methods: A retrospective anaesthesia chart analysis of all pre-eclamptic patients who underwent Caesarean Section over a 4 yr period was performed. Patient characteristic, obstetric, haemodynamic, fetal and neonatal data were gathered and analysed according to the anaesthetic technique used. Results: Seventy-seven pre-eclamptic parturients undergoing Caesarean section were identified (26 women were severely pre-eclamptic and 51 demonstrated mild pre-eclampsia). Epidural anaesthesia was performed in 62 patients and combined spinal-epidural anaesthesia was performed in 15. No differences in patient characteristic and obstetric data were noted. Highest mean arterial pressure prior to anaesthesia was comparable between the groups (epidural: 106 ± 12 vs. combined spinal-epidural anaesthesia: 109 ± l8mmHg)as well as the lowest recorded mean arterial pressure Following anaesthesia (epidural: 93 ± 13 vs. combined spinal-epidural anaesthesia: 98 ± 17 mmHg). In (he combined spinal-epidural anaesthesia group more ephedrine was used compared to the epidural group(14.6 ± 4.4 vs. 3.6 ± 4.6 mg, P < 0.05). However, more lactated Ringer's was used in the epidural group. Umbilical artery pH was lower in the epidural group (7.26 ± 0.01 vs. 7.29 ± 0.02, P < 0.05). Similar results were noted in 26 severely pre-eclamptic patients. Seven women underwent combined spinal- epidural anaesthesia and 19 underwent epidural anaesthesia in the severely pre-eclamptic group. Also more ephedrine was used in the combined spinal-epidural anaesthesia group. A tendency towards a lower umbilical artery ph was observed in the epidural group but this difference did not reach statistical significance. Conclusion: Combined spinal-epidural anaesthesia appears to be safe as anaesthetic technique for pre-eclampsia and severe pre-eclampsia. However, it is important to consider the retrospective design of the study and the large number of epidural anaesthetics performed. [ABSTRACT FROM AUTHOR]

We evaluated a new, ultra-fast response continuous cardiac output monitor in 34 adult patients undergoing off-pump coronary artery bypass graft surgery. Cardiac output was measured with the TruCCOMS® continuous cardiac output monitor (Aortech International plc, Lanarkshire, UK), using triplicate cold bolus thermodilution as the criterion standard, at fixed time points during surgery and during dobutamine infusion. The two techniques were compared using linear regression and Bland-Altman analysis. Overall, the study device displayed a bias of 0.4 l.min−1 with limits of agreement of +2.5 l.min−1 and −1.7 l.min−1. The study device failed to detect the change in cardiac output caused by dobutamine accurately ( y = 0.18 x + 0.45; r2 = 0.13), with an error linearly related to the magnitude of the change measured. We conclude that the device's failure to detect changes in cardiac output could be a major limitation in its clinical use in its current form. [ABSTRACT FROM AUTHOR]

This article reviews two recently established methods to compute sensitivities of some core parameters to basic nuclear data. First, perturbation theory offers an efficient way to compute sensitivities to nuclear parameters in continuous energy transport simulations: making use of the Iterated Fission Probability method, and by coupling the Monte Carlo code TRIPOLI-4® to the nuclear evaluation code CONRAD, we were able to compute the sensitivity of core reactivity to nuclear parameters for simple ICSBEP benchmarks. Second, using a multipoint description of a nuclear system and deterministic transport calculations the sensitivity of the state eigenvector of the system to multigroup nuclear data is computed using simple and fast partial importance calculations.

Integral experiments in reactors or critical configurations claim to have very small experimental and technological uncertainties. Therefore these latter can be considered valuable experimental information in nuclear data evaluation. Because in the evaluation process the information is carried by model parameters, to perform a rigorous feedback on a nuclear model parameters p - for instance using a measured reactivity ρ-sensitivities S =∂ρ/ρ⁄∂p/p are needed. In usual integral feedbacks, sensitivity to multi-group cross sections are first obtained with deterministic code using perturbation theory. Then these multi-group cross section sensitivities are “convoluted” with parameter sensitivities in order to provide the sensitivity on nuclear model parameter. Recently stochastic approaches have been elaborated in order to obtain continuous cross-section sensitivities thus avoiding the multi-group discretization. In the present work we used the recent Iterated Fission Probability method of the TRIPOLI4 code [1] in order to obtain directly the sensitivity to nuclear physics parameters. We focus here on the sensitivity on resonance parameters and exemplified the method on the computation of sensitivities for 239Pu and 16O resonance parameters one the ICSBEP benchmark PST001. The underlying nuclear model describing resonant cross sections are based in the R-matrix formalism [2] that provides not only the interaction cross sections but also the angular distribution of the scattered neutrons i.e. differential cross sections. The method has thus been updated in order to compute parameter sensitives that include both contributions: cross section and angular distributions. This extension of the method was tested with exact perturbation of angular distribution and fission spectrum.