Finite element analysis on the capacity of circular concrete-filled double-skin steel tubular (CFDST) stub columns

YesThis paper presents the behaviour of circular concrete-filled double-skin steel tubular (CFDST) stub columns compressed under concentric axial loads. To predict the performance of such columns, a finite element analysis is conducted. Herein, for the accurate modelling of the double-skin specimens, the identification of suitable material properties for both the concrete infill and steel tubes is crucial. The applied methodology is validated through comparisons of the results obtained from the finite element analysis with those from past experiments. Aiming to examine the effect of various diameter-to-thickness (D/t) ratios, concrete cube strengths and steel yield strengths on the overall behaviour and ultimate resistance of the double-skin columns, a total of twenty-five models are created to conduct the parametric study. In addition, four circular concrete-filled steel tubes (CFST) are included to check the dissimilarities, in terms of their behaviour and weight, when compared with identical double-skin tubes. A new formula based on Eurocode 4 is proposed to evaluate the strength of the double-skin specimens. Based on the comparison between the results derived from the analysis, the proposed formulae for the concrete filled double-skin would appear to be satisfactory

Validation of a Non-invasive Inverse Problem-Solving Method for Stroke Volume.

Stroke volume (SV) is a major biomarker of cardiac function, reflecting ventricular-vascular coupling. Despite this, hemodynamic monitoring and management seldomly includes assessments of SV and remains predominantly guided by brachial cuff blood pressure (BP). Recently, we proposed a mathematical inverse-problem solving method for acquiring non-invasive estimates of mean aortic flow and SV using age, weight, height and measurements of brachial BP and carotid-femoral pulse wave velocity (cfPWV). This approach relies on the adjustment of a validated one-dimensional model of the systemic circulation and applies an optimization process for deriving a quasi-personalized profile of an individual's arterial hemodynamics. Following the promising results of our initial validation, our first aim was to validate our method against measurements of SV derived from magnetic resonance imaging (MRI) in healthy individuals covering a wide range of ages (n = 144; age range 18-85 years). Our second aim was to investigate whether the performance of the inverse problem-solving method for estimating SV is superior to traditional statistical approaches using multilinear regression models. We showed that the inverse method yielded higher agreement between estimated and reference data (r = 0.83, P < 0.001) in comparison to the agreement achieved using a traditional regression model (r = 0.74, P < 0.001) across a wide range of age decades. Our findings further verify the utility of the inverse method in the clinical setting and highlight the importance of physics-based mathematical modeling in improving predictive tools for hemodynamic monitoring

Videolaryngoscopy in the management of the difficult airway: A comparison with the Macintosh blade

Background and objective: Several studies have shown that videolaryngoscopes can provide better laryngeal exposure than conventional laryngoscopy. These studies, however, did not exclusively focus on patients with an anticipated difficult intubation. The aim of the present study was to assess whether a videolaryngoscope would provide better laryngeal exposure than conventional laryngoscopy and therefore facilitate intubation in cases of difficult laryngoscopy. Methods One hundred and twelve patients with an estimated difficult intubation, scheduled to undergo surgical operations, requiring general anaesthesia and endotracheal intubation, were included in the study. Direct laryngoscopy with a Macintosh blade was performed, followed by videolaryngoscopy and intubation attempt(s). The laryngeal views obtained by each method were recorded according to the Cormack/Lehane scale. Results: The percentage of Cormack-Lehane I and II views obtained by conventional laryngoscopy rose from 63.4 to 90.2% (P&lt;0.0005) with videolaryngoscopy, whereas Cormack-Lehane III and IV views declined from 36.6 to 9.8% (P&lt;0.0005). Intubation was successful in 98.2% of the cases. Conclusion: In patients with an anticipated difficult airway, videolaryngoscopy significantly improved the laryngeal exposure thus facilitating endotracheal intubation. © 2009 European Society of Anaesthesiology

Pharmacokinetics of moxifloxacin in non-inflamed cerebrospinal fluid of humans: Implication for a bactericidal effect

Objectives: To evaluate the ability of moxifloxacin to penetrate healthy brain barriers. Methods: Fifty patients received a single oral dose of 400 mg as an antimicrobial prophylaxis regimen for a short urological procedure under spinal anaesthesia. Serum and cerebrospinal fluid (CSF) were sampled at different time intervals post-drug intake and patients were divided into five groups, as follows: group I: 0.5-1 h; group II: 1-2 h; group III: 2-4 h; group IV: 4-6 h; and group V: 6-8 h. Concentrations of moxifloxacin were estimated after analysis by an HPLC system. Bactericidal activity of CSF samples of groups III and IV was assessed by a microdilution technique against two penicillin-resistant isolates of Streptococcus pneumoniae with MICs of moxifloxacin of 0.19 and 0.125 mg/L, respectively. Results: Mean CSF concentrations of moxifloxacin of groups I, II, III, IV and V were 0.19, 0.87, 3.00, 4.07 and 1.82 mg/L, respectively. The mean bactericidal activity of CSF of group III was 8 and that of group IV was 4. Conclusions: Single oral intake of 400 mg moxifloxacin is accompanied by good penetration through healthy meninges within 2-6 h post-dose and reached adequately high levels in human CSF exerting satisfactory bactericidal activity against penicillin-resistant S. pneumoniae. These results render novel perspectives for a role of moxifloxacin in CNS infections. © The Author 2008. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved

Cerebrospinal fluid of patients administered moxifloxacin modulates the secretion of cytokines from human monocytes

To evaluate the ex vivo immunomodulatory properties of moxifloxacin, we applied serum and cerebrospinal fluid (CSF) samples from 50 patients who received a single oral dose of 400 mg. Patients were divided into 5 groups according to time lapsing between sampling and drug intake: group I, 0.5 to 1 h; group II, 1 to 2 h; group III, 2 to 4 h; group IV, 4 to 6 h; and group V, 6 to 8 h. Samples were added to cultures of U937 monocytes stimulated by 10 ng/mL of lipopolysaccharide (LPS) and 1 × 105 colony-forming unit (CFU) of 1 heat-killed penicillin-resistant isolate of Streptococcus pneumoniae. Concentrations of cytokines were estimated in supernatants. Concentrations of interleukin (IL)-1β, IL-10, and IL-12 released after stimulation by LPS were significantly decreased by CSF of groups I, IV, and V. After stimulation by the heat-killed isolate, concentrations of tumor necrosis factor α (TNF-α), IL-1β, IL-6, and IL-10 were increased in the presence of CSF of group III; those of IL-12p70 were decreased by CSF of groups I and II. Concentrations of IL-1β, IL-6, and IL-8 drawn after stimulation by LPS were significantly decreased upon addition of serum from all groups. After stimulation by the heat-killed isolate, concentrations of TNF-α were decreased by serum drawn from all patients; IL-1β was increased after addition of serum of groups I, II, and V. It is concluded that CSF and serum of patients administered moxifloxacin may effectively modulate the production of pro- and anti-inflammatory cytokines by human monocytes. These results render new perspectives for the therapy for meningitis. © 2008 Elsevier Inc. All rights reserved