Time domain modeling of self-excited aerodynamic forces for cable-supported bridges: A comparative study

Prediction of the wind-induced dynamic response of suspension bridges, emphasizing self-excited forces, is discussed in this paper. The self-excited forces have been modeled by two commonly applied unsteady models and an unsteady model introduced and explained in this article. A novel frequency-independent approximation of the self-excited forces, which for the suspension bridge considered provides results as accurate as those from the unsteady models, is also presented. An integration method that may reduce the number of time steps necessary to avoid amplitude and phase distortion of the self-excited forces has been introduced and applied successfully in a comprehensive case study.     

Along-wind response of suspension bridges with special reference to stiffening by horizontal cables

This paper outlines the application of the theory of stochastic dynamics to evaluate the forced response of suspension bridges subjected to gusty winds. The main emphasis is placed on the analysis of the along-wind response and complete formulae for the root-mean-square response are worked out. The concept of gust response factors is also discussed. The effects of lateral cables as a means to reduce the along-wind response is dealt with. Numerical results of four suspensions bridges with centre spans in the range 525–1250 m are presented, including a discussion of the general trend of the along-wind response.     

Optimization of activated carbon‐based decontamination of fish oil by response surface methodology

The effect of activated carbon (AC) adsorption on the reduction of persistent organic pollutants (POP) in fish oil was studied based on response surface methodology at a 5‐g/kg AC inclusion level. Pretreatment of the oil by alkali refining and bleaching increased the POP levels. The tested process variables (contact time and temperature) affected the AC adsorption rate and significant first‐ and second‐order response models could be established. Polychlorinated dibenzo‐p‐dioxins and dibenzofurans (PCDD/F) showed a very rapid adsorption behavior and the concentration and toxic equivalent (TEQ) level could be reduced by 99%. Adsorption of dioxin‐like polychlorinated biphenyls (DL‐PCB) was less effective and depended on ortho substitution, i.e. non‐ortho PCB were adsorbed more effectively than mono‐ortho PCB with a maximum of 87 and 21% reduction, respectively, corresponding to a DL‐PCB‐TEQ reduction of 73%. A common optimum for both PCDD/F and DL‐PCB adsorption could not be identified. AC treatment had no effect on the level of polybrominated diphenyl ether flame retardants. The differences in adsorption patterns may be explained based on molecular conformation. No change in oil quality could be observed based on oxidation parameters. Compliance with present PCDD/F and DL‐PCB legislation levels in fish oil can be achieved based on AC adsorption.     

On transient species and activation energies in heterogeneous catalysis

A discussion is presented on the relation between true and apparent activation energies found in heterogeneous catalysis. The possibility of a transient species defining the rate determining step is emphasized. In such a case, the difference between apparent and true activation energies can be quite small. Such a condition is of importance for the understanding of phenomena involving the activation energy, such as the isokinetic effect.     

Cardioprotective Properties of Mannitol—Involvement of Mitochondrial Potassium Channels

Cardiac preconditioning (PC) and postconditioning (PoC) are powerful measures against the consequences of myocardial ischemia and reperfusion (I/R) injury. Mannitol—a hyperosmolar solution—is clinically used for treatment of intracranial and intraocular pressure or promotion of diuresis in renal failure. Next to these clinical indications, different organ-protective properties—e.g., perioperative neuroprotection—are described. However, whether Mannitol also confers cardioprotection via a pre- and/or postconditioning stimulus, possibly reducing consequences of I/R injury, remains to be seen. Therefore, in the present study we investigated whether (1) Mannitol-induced pre- and/or postconditioning induces myocardial infarct size reduction and (2) activation of mitochondrial ATP-sensitive potassium (mK_ATP) channels is involved in cardioprotection by Mannitol. Experiments were performed on isolated hearts of male Wistar rats via a pressure controlled Langendorff system, randomized into 7 groups. Each heart underwent 33 min of global ischemia and 60 min of reperfusion. Control hearts (Con) received Krebs–Henseleit buffer as vehicle only. Pre- and postconditioning was achieved by administration of 11 mmol/L Mannitol for 10 min before ischemia (Man-PC) or immediately at the onset of reperfusion (Man-PoC), respectively. In further groups, the mK_ATP channel blocker 5HD, was applied with and without Mannitol, to determine the potential underlying cardioprotective mechanisms. Primary endpoint was infarct size, determined by triphenyltetrazolium chloride staining. Mannitol significantly reduced infarct size both as a pre- (Man-PC) and postconditioning (Man-PoC) stimulus compared to control hearts (Man-PC: 31 ± 4%; Man-PoC: 35 ± 6%, each p < 0.05 vs. Con: 57 ± 9%). The mK_ATP channel inhibitor completely abrogated the cardioprotective effect of Mannitol-induced pre- (5HD-PC-Man-PC: 59 ± 8%, p < 0.05 vs. Man-PC) and postconditioning (5HD-PoC-Man-PoC: 59 ± 10% vs. p < 0.05 Man-PoC). Infarct size was not influenced by 5HD itself (5HD-PC: 60 ± 14%; 5HD-PoC: 54 ± 14%, each ns vs. Con). This study demonstrates that Mannitol (1) induces myocardial pre- and postconditioning and (2) confers cardioprotection via activation of mK_ATP channels.     

A discrete de Rham complex with enhanced smoothness

Abstract Discrete de Rham complexes are fundamental tools in the construction of stable elements for some finite element methods. The purpose of this paper is to discuss a new discrete de Rham complex in three space dimensions, where the finite element spaces have extra smoothness compared to the standard requirements. The motivation for this construction is to produce discretizations which have uniform stability properties for certain families of singular perturbation problem. In particular, we show how the spaces constructed here lead to discretizations of Stokes type systems which have uniform convergence properties as the Stokes flow approaches a Darcy flow. Keywords: Discrete exact sequences, nonconforming finite elements, Darcy–Stokes flow, uniform error estimates. Mathematics Subject Classification (1991): Primary 65N12, 65N15, 65N30     

High-dose chemotherapy with carboplatin, etoposide and ifosfamide followed by autologous stem cell rescue in patients with relapsed or refractory malignant lymphomas: a phase I/II study

Patients with relapsed or refractory non-Hodgkin's lymphomas (NHL) and Hodgkin's disease (HD) with recurrences after an anthracyclin-containing regimen only have a chance of cure of below 10% with conventional chemotherapy. In order to improve their prognosis, we started a phase I/II trial using high-dose therapy comprising carboplatin, together with etoposide and ifosfamide (CEI), followed by autologous stem cell rescue (ASCR) as consolidation after salvage treatment. Since September 1990, 40 patients with intensively pretreated advanced NHL (n = 24) or HD (n = 16) received one cycle of high-dose therapy (HDT) consisting of carboplatin 1500 mg/m2, ifosfamide 10 g/m2 and etoposide in escalating doses from 1200 mg/m2 to 2400 mg/m2 followed by ASCR. Thirty-nine patients were assessable for toxicity and response. The following doses appeared to be safe: carboplatin 1500 mg/m2, etoposide 2400 mg/m2 and ifosfamide 10 g/m2. All patients developed grade 3 nausea and grade 3 or 4 mucositis. Granulocytopenic fever occurred in 100% with grade 4 infections in 15%. Mild transient kidney toxicity was noted in 36% and liver toxicity in 20% of patients. One toxic death occurred (2.5%). Objective responses were obtained in 36 of 39 patients (92%) with complete remissions (CR) in 24 patients (61.5%) and partial remissions (PR) in 12 (30.7%). Median observation time for surviving patients was 23.3 months (range 3.4-52.3). The probabilities of overall, event-free and relapse-free survival at 2 years are 62, 39 and 55%, respectively. Patients with primary refractory disease or resistant relapse had a poor prognosis. High-dose carboplatin, etoposide and ifosfamide plus autologous stem cell rescue represents an effective, potentially curative salvage treatment with acceptable toxicities.