Early and late results of surgical treatment in patients with primary mediastinal germ cell tumors]

A group of 37 patients--20 (54%) men and 17 (46%) women--aged 2-65, mean 31.6 years, was treated between 1978 and 1995 for different kinds of primary mediastinal germ cell tumours. In 14 (37.8%) of them a mature solid teratoma was diagnosed, in 13 (35.1%)--dermoid cyst, in 5 (13.5%)--malignant teratoma, in 1 (2.7%)--immature teratoma, in 4 (10.8%)--seminoma. Mediastinal tumour was removed completely in 30 (81.1%) patients, partially in 7 (18.9%). Out of 37 patients, 3 (8.1%) died during postoperative time. Out of 26 patients discharged after surgical removal of mature teratomas, all are alive and have been followed-up for 10 years (17 patients) or 5 years (6 patients). Out of 8 discharged after surgical removal of malignant neoplasm, 3 are alive and all of them had primary mediastinal seminoma. One of them has survived 17 years after complete resection, and two patients--7.5 years and 2 years after partial resection and radiotherapy. Mean survival time is 4 years and 2 months for all patients with malignant neoplasm.     

A Geometric Approach to Solving Problems of Control Constraints: Theory and a DAE Framework

The paper deals with controlled mechanical systems in which the number of control inputs is equal to the number of desired system outputs, and is smaller than the number of degrees of freedom of the system. The determination of control input strategy that force the underactuated system to complete the partly specified motion is a challenging problem. In the present formulation, the outputs (performance goals), expressed in terms of system states, are treated as constraints on the system—called control or program constraints as distinct from contact constraints in the classical sense, and a mathematical resemblance of the inverse control problem to the constrained system dynamics is exploited. However, while the reactions of contact constraints act in the directions orthogonal to the respective constraint manifold, the available control reactions may have arbitrary directions with respect to the program constraint manifold, and in the extreme may be tangent. A specific methodology must then be developed to find the solution of such singular problems, related to a class of control tracking problems such as position control of elastic joint robots, control of cranes, and aircraft control in prescribed trajectory flight. The governing equations of the problem arise as a set of differential-algebraic equations (DAEs), and an effective method for solving the DAEs, based on backward Euler method, is proposed. The open-loop control formulation obtained this way is then extended by a closed-loop control law to provide stable tracking of the required reference trajectories in the presence of perturbations. Some examples of applications of the theory and results of numerical simulations are reported.     

Optimization of evaporative fluid coolersOptimisation des refroidisseurs de liquide évaporatifs

In the paper the optimization of geometrical and operating parameters for evaporative fluid coolers has been presented. The algorithm of optimizational calculations contains:

• the mathematical model of heat and mass transfer in evaporative fluid coolers;

• model of operating costs based, among others, on the Zalewski–Gryglaszewski relations developed by the authors for evaluation of air pressure drops in the heat exchanger;

• model of evaporative heat exchangers production costs.

Optimization problem formulated for non-linear objective functions with inequality and equality constraints has been solved using Schittkowski's method based on quadratic programming. Two optimization problems have been considered. A solution to the first problem consists in the design of a heat exchanger with such geometrical parameters which ensure its maximum heat capacity at minimal total costs. A result to the second optimization problem are such thermal and flow parameters which will ensure minimum operating costs.The results of optimization calculations presented in the paper are accompanied by their experimental verification.     

The use of Path Tracking Method for determining the tortuosity field in a porous bed

The article is related to a computational method of obtaining the geometric tortuosity in granular beds, i.e. polydisperse beds consisting of spherical or quasi-spherical particles, freely distributed in the 3D space. The main aim is to show a new way of calculating two-dimensional tortuosity distribution in the plane perpendicular to the chosen direction in the space (interpreted as the main flow direction) by the use of own computational algorithm, the so-called Path Tracking Method (PTM). This way links the ability of the PTM to analyze relatively large granular beds due to low demand for computing power and the possibility of obtaining the tortuosity distribution in the space. Although this distribution is only 2D (there is only one value for every discrete point in the plane perpendicular to the main flow direction), it may be useful for estimation of the local pressure drops in fluid flows through granular bed. To reach the aim, the PTM has been improved and its application here is shown in a new context.     

Positive real control of two-dimensional systems: Roesser models and linear repetitive processes

This paper considers the problem of positive real control for two-dimensional (2-D) discrete systems described by the Roesser model and also discrete linear repetitive processes, which are another distinct sub-class of 2-D linear systems of both systems theoretic and applications interest. The purpose of this paper is to design a dynamic output feedback controller such that the resulting closed-loop system is asymptotically stable and the closed-loop system transfer function from the disturbance to the controlled output is extended strictly positive real. We first establish a version of positive realness for 2-D discrete systems described by the Roesser state space model, then a sufficient condition for the existence of the desired output feedback controllers is obtained in terms of four LMIs. When these LMIs are feasible, an explicit parameterization of the desired output feedback controllers is given. We then apply a similar approach to discrete linear repetitive processes represented in their equivalent 1-D state-space form. Finally, we provide numerical examples to demonstrate the applicability of the approach.     

Studies on some properties of poly(phenylene sulphide)

Poly(phenylene sulphide) was synthesized by a direct method. Benzene and elemental sulphur were used as substrates, and aluminium chloride as a catalyst. The obtained final product was characterized by IR, VIS-UV, wide angle X-ray and mass spectroscopy, thermal, and elemental analyses. On the base of the analytical methods the molecular structure of the obtained polymer was discussed.     

Hydrophilic polycarbonate chips for generation of oil-in-water (O/W) and water-in-oil-in-water (W/O/W) emulsions

Modification of the surfaces of polycarbonate (PC) with the use of a solution of tin (II) chloride renders them hydrophilic. The surface draping is stable against exposure to water and to alcohols. Exposure to alkanes reduces but does not diminish the effect. The method is compatible—in using the same solvent and temperature—with the hydrophobic modification of PC (Jankowski et al. in Lab Chip 11:1151–1156, 2011). The combination of these methods makes it possible to generate single and multiple monodisperse emulsions with the use of flow-focusing junctions in systems made in PC—a material that is suitable for fabrication of multilayer, high-throughput microfluidic devices.     

Integrated instrumental analysis of soft brown coals

A method for the simultaneous determination of calorific value Q^r, ash yieldA^r and total water content W^r_t of soft brown coals is described. The method involves instrumental analysis of brown coal samples using neutron thermalization and gamma back-scattering techniques. Over 80 coal samples (1.1 kg) were analysed, having Q^rvalues up to 15.5 MJ kg^?1,A^r ranging from 3.6 to 76.1 wt% and W^r_t ranging from 11.4 to 61.7 wt%. A comparison of the results from the instrumental method with those of standard laboratory analyses is given, followed by a discussion of the accuracy of the method and of possible ways for improving it.     

Synthesis and self-association in aqueous media of poly(ethylene oxide)/poly(ethyl glycidyl carbamate) amphiphilic block copolymers

New temperature sensitive AB, ABA, and BAB amphiphilic block copolymers consisting of hydrophilic poly(ethylene oxide) and hydrophobic poly(ethyl glycidyl carbamate) blocks were synthesized by anionic polymerization followed by chemical modification reactions. The self-association of the block copolymers in aqueous media was studied by UV-vis spectroscopy and dynamic and static light scattering. The obtained block copolymers spontaneously form micelles in aqueous media. The critical micellization concentration varied from 0.5 to 4 g/L depending on the copolymer architecture and composition. The influence of the temperature upon the self-association of the block copolymers was investigated. The increase of temperature did not affect the value of the critical micellization concentration, but led to the formation of better defined micelles with narrow size distribution.     

Double-Headed Cationic Lipopeptides: An Emerging Class of Antimicrobials

Antimicrobial peptides (AMPs) constitute a promising tool in the development of novel therapeutic agents useful in a wide range of bacterial and fungal infections. Among the modifications improving pharmacokinetic and pharmacodynamic characteristics of natural AMPs, an important role is played by lipidation. This study focuses on the newly designed and synthesized lipopeptides containing multiple Lys residues or their shorter homologues with palmitic acid (C₁₆) attached to the side chain of a residue located in the center of the peptide sequence. The approach resulted in the development of lipopeptides representing a model of surfactants with two polar headgroups. The aim of this study is to explain how variations in the length of the peptide chain or the hydrocarbon side chain of an amino acid residue modified with C₁₆, affect biological functions of lipopeptides, their self-assembling propensity, and their mode of action.