Quantitation of cell-associated doxorubicin by high-performance liquid chromatography after enzymatic desequestration

In a double blind study of 58 episodes of fever and profound neutropenia, children with cancer received either recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) or placebo, combined with identical antimicrobial therapy, i.e. imipenem, on admission. The criteria for discontinuation of therapy were identical. A difference was demonstrated both in the number of hospital days, totaling 252 days in the rhGM-CSF group and 354 in the placebo group, days receiving antibiotics (220 vs. 322), and in the resolution of neutropenia (4.5 days vs. 6.0 days; P < 0.05). The number of episodes requiring antimicrobial therapy for longer than 10 days was 5 of 28 (12%) in the rhGM-CSF group as opposed to 15 of 30 (50%) in the placebo group (P = 0.01). rhGM-CSF was well-tolerated. We conclude that rhGM-CSF was efficacious in accelerating myeloid recovery and reducing the length of hospitalization in febrile neutropenia.     

Buckling and postbuckling of circular plates containing concentric penny-shaped delaminations

Buckling and postbuckling analyses of circular laminated composite plates with delaminations are presented. An axisymmetric finite element model based on a layer-wise laminated composite plate theory is developed to formulate the problem. Geometric nonlinearity in the sense of von Kármán and imperfections in the form of initial global deflection and initial delamination openings are included. A simple contact algorithm which precludes the physically inadmissible overlapping between delaminated surfaces is proposed and incorporated into the analysis.

Numerical results are obtained addressing the effects of the initial imperfections, the number of delaminations and their sizes on the critical buckling load and buckling mode shapes as well as postbuckling responses.     

Optimization of nonlinear trusses using a displacement-based approach

A displacement-based optimization strategy is extended to the design of truss structures with geometric and material nonlinear responses. Unlike the traditional optimization approach that uses iterative finite element analyses to determine the structural response as the sizing variables are varied by the optimizer, the proposed method searches for an optimal solution by using the displacement degrees of freedom as design variables. Hence, the method is composed of two levels: an outer level problem where the optimal displacement field is searched using general nonlinear programming algorithms, and an inner problem where a set of optimal cross-sectional dimensions are computed for a given displacement field. For truss structures, the inner problem is a linear programming problem in terms of the sizing variables regardless of the nature of the governing equilibrium equations, which can be linear or nonlinear in displacements. The method has been applied to three test examples, which include material and geometric nonlinearities, for which it appears to be efficient and robust. Received December 4, 2000     

Fiber path definitions for elastically tailored conical shells

Elastic stiffness tailoring of laminated composite panels by allowing the fibers to curve within the plane of the laminae has proven to be beneficial and practical for flat rectangular plate designs. In this paper the field of application of this variable-stiffness concept is extended to three-dimensional conical shells with arbitrary dimensions that can be fabricated using advanced fiber placement machines. This paper presents the detailed derivation of four theoretical fiber path definitions for generalized conical shell surfaces. The different path definitions and resulting laminate geometries are discussed. Implementation of fabrication details and constraints in terms of the steering radius of curvature based on advanced tow-placement technology are demonstrated.     

Design of variable-stiffness composite panels for maximum buckling load

A generalized reciprocal approximation is presented for design of variable-stiffness laminated composite panels for maximum buckling load. The buckling load is expanded in terms of the inverse of the stiffness tensor. For discretized panels such an approximation has the important property of being separable, which allows the maximization to be carried out at each discrete node separate from the others. This makes the algorithm particularly suited to parallel computations. The sensitivity analysis is performed exactly using an adjoint method, requiring only one back substitution using the already factored inplane stiffness matrix with different right hand sides to compute the sensitivities for all design variables. A conforming CLPT finite element is used for the buckling analysis of rectangular plates and the proposed reciprocal approximation is used to update fiber orientation angles at each finite element node. Numerical results obtained for rectangular plates show that significant improvements can be gained in the buckling load by allowing the stiffness properties to vary spatially. The case of repeated eigenvalues is handled using a dual formulation.     

Low-velocity impact damage on dispersed stacking sequence laminates. Part I: Experiments

The stacking sequence design of composite laminates is often limited to combinations of 0°, 90°, and ±45° fibre angle plies. Furthermore, in order to comply to certain stiffness requirements, clustering of plies becomes unavoidable. Although such laminates might have the desired stiffness properties, they may show poor impact and/or compression-after-impact behaviour.A method to redesign the traditional stacking sequences such that the alternative laminates have improved damage resistance whilst keeping similar in-plane and bending stiffness properties as their original traditional stacking sequences is proposed. This method makes use of optimisation tools based on genetic algorithms. In the alternative laminates, the difference between fibre angles of two consecutive plies is maximised and allowed to vary in the 0–90° fibre angle range at intervals of 5°. Manufacturing of such laminates is practical nowadays as the industry is changing its production techniques into accurate automated fibre-placement and tape-laying technologies. A two-step approach is proposed for the design of laminates. In the first step, the optimal laminate is designed in the traditional fashion to cope with the expected quasi-static loads on the structure. The second step consists of redesigning this laminate to better withstand impact loads by dispersing its stacking sequence while keeping similar stiffness properties as in the first step.A traditional laminate and two dispersed stacking sequence alternative layups were tested under low-velocity impact and compression-after-impact loads in order to compare their impact resistance and damage tolerance characteristics. The evaluation of these laminates will also be carried out by the innovative numerical tools proposed in the follow-up of the present paper.     

A Koiter‐Newton approach for nonlinear structural analysis

A new approach termed the Koiter‐Newton is presented for the numerical solution of a class of elastic nonlinear structural response problems. It is a combination of a reduction method inspired by Koiter's post‐buckling analysis and Newton arc‐length method so that it is accurate over the entire equilibrium path and also computationally efficient in the presence of buckling. Finite element implementation based on element independent co‐rotational formulation is used. Various numerical examples of buckling sensitive structures are presented to evaluate the performance of the method. The examples demonstrate that the method is robust and completely automatic and that it outperforms traditional path‐following techniques. This improved efficiency will open the door for the direct use of detailed nonlinear finite element models in the design optimization of next generation flight and launch vehicles. Copyright © 2013 John Wiley & Sons, Ltd.     

Gas adsorption capacity of Carboniferous coals in the Zonguldak basin (NW Turkey) and its controlling factors

The aim of this study is the determination of the gas adsorption capacity of Carboniferous coals in the Zonguldak basin, NW Turkey and its controlling factors. Investigated coals are typical humic coals rich in vitrinite and are high to medium volatile bituminous in rank. In order to determine gas adsorption capacity of coals, carbon dioxide gas adsorption isotherms are obtained by gas flow controlled and volumetric adsorption methods. BET, Langmuir and D–R equations were used to interpret the adsorption isotherms. Respective values of the BET, Langmuir and Dubinin–Radushkevich (D–R) adsorbed carbon dioxide volume vary between 2–13, 5–36 and 10–48 cm³/g at STP. Langmuir monolayer gas volume is considered as the gas adsorption capacity of the coals. The variations in this capacity have been examined by correlation with different coal properties determined with the help of geochemical, organic geochemical, and organic petrographical methods. Additionally, micropore volume which is determined using the D–R equation is correlated with coal rank and maceral type, and ash content.