On The Buckling of Fiber-Bundle Type Beams

Euler was the first who studied for engineering applications important problem of buckling arising in a simple, monolithic beam loaded axially by a concentrated load. As it has been shown from two solutions of the problem due to Timosenko theory, the elastic foundation increases the critical buckling load of the beam. Starting from the previous classical results, a mechanism to enhance the buckling strength of a cantilevered beam is investigated. In the place of a single, one-element, monolithic cross-section, the use of a bundle of more than one, similar or not, single cross-sections, placed with parallel axes, and staying in free (unilateral) contact along their adjacent boundaries, is proposed

Evolution of antimicrobial prophylaxis in cardiovascular surgery

Objective: To examine the optimal duration of antibiotic prophylaxis in major cardiovascular surgery. Methods: In the past 15 years, four prospective randomized, controlled studies, conducted by the same group of authors, compared seven prophylactic antimicrobial regimens in 2970 patients undergoing major cardiovascular surgery. In 1980/81, a 4-day cefazolin (CFZ) prophylaxis was compared with a 2-day cefuroxime (CFX) administration (n=566). In 1982/83, a 2-day CFX prophylaxis was compared with a two shot ceftriaxone (CRO) prophylaxis (n=512). In 1984/87, a 1-day CFZ prophylaxis was compared with a single shot prophylaxis of CRO (n=883). In 1994/1995, a 4 day combination of amoxicillin (AM) and netilmicin (NET) prophylaxis was compared with a single shot prophylaxis of CFX (n=1009). Results: Total infection rate varied between 4.5 and 5.7%, despite different antimicrobial regimen used and their varying duration. Wound infection rate was 1.1% (range 0.4-2.5%), sepsis rate was 0.8% (range 0.4-1.6%), pneumonia rate 2% (0.7-2.9%), urinary tract infection rate 0.4% (range 0-1.4%), and central venous catheter-related infection rate was 0.4% (0-1%). The 30-day mortality rate was 1.3% (range 0.4-2%). All these differences were not statistically significant. Conclusions: A low infection rate (range 4.5-5.7%) occurred despite changes in duration of various prophylactic antibiotic regimen with cephalosporins of first, second or third generation. As a single shot prophylaxis could nowadays successfully be used in cardiovascular surgery, no postoperative antibiotics should be used, unless an intraoperative or a postoperative infection is documented or in presence of major perioperative complication

Passive Control of Bridges

In the design of bridges with large spans, the significant values of the moments at the main deck-structure require very heavy members, either in the case of a beam or a truss deck-structure. In order to minimize the influence of bending moments, several applications of passive control of displacements using cable nets are herein proposed. The base for all the proposed systems is the cables supported beam nets with additional prestressing control on support cables to optimize the structural behavior of the system. The passive control design problem leads to an optimal control problem for structures governed by variational inequalities. In this presentation several bridge systems are proposed and studied as applications of this method

Worldwide research productivity in critical care medicine

INTRODUCTION: The number of publications and the impact factor of journals are accepted estimates of the quantity and quality of research productivity. The objective of the present study was to assess the worldwide scientific contribution in the field of critical care medicine. METHOD: All research studies published between 1995 and 2003 in medical journals that were listed in the 2003 Science Citation Index (SCI(®)) of Journal Citation Reports under the subheading 'critical care' and also indexed in the PubMed database were reviewed in order to identify their geographical origin. RESULTS: Of 22,976 critical care publications in 14 medical journals, 17,630 originated from Western Europe and the USA (76.7%). A significant increase in the number of publications originated from Western European countries during the last 5 years of the study period was noticed. Scientific publications in critical care medicine increased significantly (25%) from 1995 to 2003, which was accompanied by an increase in the impact factor of the corresponding journals (47.4%). Canada and Japan had the better performance, based on the impact factor of journals. CONCLUSION: Significant scientific progress in critical care research took place during the period of study (1995–2003). Leaders of research productivity (in terms of absolute numbers) were Western Europe and the USA. Publications originating from Western European countries increased significantly in quantity and quality over the study period. Articles originating from Canada, Japan, and the USA had the highest mean impact factor.. Canada was the leader in productivity when adjustments for gross domestic product and population were made

Impact of Definitive Therapy with Beta-Lactam Monotherapy or Combination with an Aminoglycoside or a Quinolone for Pseudomonas aeruginosa Bacteremia

BACKGROUND: Bacteremia by Pseudomonas aeruginosa represents one severe infection. It is not clear whether beta-lactam monotherapy leads to similar rates of treatment success compared to combinations of beta-lactams with aminoglycosides or quinolones. METHODS: Retrospective cohort study from 3 tertiary hospitals (2 in Greece and 1 in Italy). Pseudomonas aeruginosa isolates were susceptible to a beta-lactam and an aminoglycoside or a quinolone. Patients received appropriate therapy for at least 48 hours. Primary outcome of interest was treatment success in patients with definitive beta-lactam combination therapy compared to monotherapy. Secondary outcomes were treatment success keeping the same empirical and definitive regimen, mortality, and toxicity. RESULTS: Out of 92 bacteremias there were 54 evaluable episodes for the primary outcome (20 received monotherapy). Treatment success was higher with combination therapy (85%) compared to beta-lactam monotherapy (65%), however not statistically significantly [Odds ratio (OR) 3.1; 95% Confidence Interval (CI) 0.69-14.7, p = 0.1]. Very long (>2 months) hospitalisation before bacteremia was the only factor independently associated with treatment success (OR 0.73; 95% CI 0.01-0.95, p = 0.046), however this result entailed few episodes. All-cause mortality did not differ significantly between combination therapy [6/31 (19%)] and monotherapy [8/19 (42%)], p = 0.11. Only Charlson comorbidity index was associated with excess mortality (p = 0.03). CONCLUSION: Our study, in accordance with previous ones, indicates that the choice between monotherapy and combination therapy may not affect treatment success significantly. However, our study does not have statistical power to identify small or moderate differences. A large randomized controlled trial evaluating this issue is justified