Application of Laplace transforms for the solution of transient mass- and heat-transfer problems in flow systems

A fast numerical technique for the solution of partial differential equations describing timedependent two- or three-dimensional transport phenomena is developed. It is based on transforming the original time-domain equations into the Laplace domain where numerical integration is performed and by subsequent numerical inverse transformation the final solution can be obtained. The computation time is thus reduced by more than one order of magnitude in comparison with the conventional finite-difference techniques. The effectiveness of the proposed technique is demonstrated by illustrative examples

Mathematical modelling of a flow-injection system with a membrane separation module

A mathematical model for a flow-injection system with a membrane separation module based on the axially dispersed plug flow model was developed. It takes into account the geometrical dimensions and dispersion properties of the main sections of the manifold, the mass transfer in the channels of the separation module and the characteristics of the membrane (thickness and diffusion coefficient within it). The model was solved analytically in the Laplace domain. The inverse transformation was found to give satisfactory results for reactor Peclet numbers less than 120. Otherwise a numerical solution based on the implicit alternating-direction finite difference method was preferred. The adequacy of the model was confirmed experimentally on a flow-injection manifold with a parallel-plate dialysis module. The unknown flow and membrane parameters were determined by curve fitting. The membrane parameters were determined also by steady-state measurements. Fairly good agreement between the dynamic and steady-state results and with results given in the literature was observed, which, together with other experimental results, supported the validity of the model and showed that it can be used successfully for the mathematical description and optimization of flow-injection systems with membrane separation modules. In this connection, the influence of the reactor parameters and the sample volume on the performance of such a system were investigated and conclusions for improving its sensitivity and sample throughput were drawn. Other possible applications of the model are in membrane technology for characterizing of various membranes and in process engineering for investigating the mass transfer in different dialysers

Investigation on the Effect of Application of Monopolar Electrocoagulation for Endoscopic Haemostasis in Bleeding Peptic Ulcers

The authors investigate the effect of application of monopolar electrocoagulation for endoscopic haemostasis in bleeding peptic ulcers. In group of 30 randomly selected patients with acute bleeding from gastroduodenal ulcers, classified after Forrest by Wirtz we apply endoscopic electrocoagulation. The authors reveal that the method of monopolar high-frequent diathermal coagulation in present days is not appropriate for the purposes of endoscopic haemostasis in acute bleeding from gastroduodenal ulcers

Lytic and mechanical stability of clots composed of fibrin and blood vessel wall components.

Background Proteases expressed in atherosclerotic plaque lesions generate collagen fragments, release glycosaminoglycans (chondroitin sulfate [CS] and dermatan sulfate [DS]) and expose extracellular matrix (ECM) proteins (e.g. decorin) at sites of fibrin formation. Objective Here we address the effect of these vessel wall components on the lysis of fibrin by the tissue plasminogen activator (tPA)/plasminogen system and on the mechanical stability of clots. Methods and results MMP-8-digested collagen fragments, isolated CS, DS, glycosylated decorin and its core protein were used to prepare mixed matrices with fibrin (additives present at a 50-fold lower mass concentration than fibrinogen). Scanning electron microscopy (SEM) showed that the presence of ECM components resulted in a coarse fibrin structure, most pronounced for glycosylated decorin causing an increase in the median fiber diameter from 85 to 187 nm. Rheological measurements indicated that these structural alterations were coupled to decreased shear resistance (1.8-fold lower shear stress needed for gel/fluid transition of the clots containing glycosylated decorin) and rigidity (reduction of the storage modulus from 54.3 to 33.2 Pa). The lytic susceptibility of the modified fibrin structures was increased. The time to 50% lysis by plasmin was reduced approximately 2-fold for all investigated ECM components (apart from the core protein of decorin which produced a moderate reduction of the lysis time by 25%), whereas fibrin-dependent plasminogen activation by tPA was inhibited by up to 30%. Conclusion ECM components compromise the chemical and mechanical stability of fibrin as a result of changes in its ultrastructure

Introduction to “The social theories of classical political economy and modern economic policy”

This is the first-ever English translation of an 1891 essay by Carl Menger published in the most important newspaper of the Habsburg Empire, the Neue Freie Presse. Menger writes the piece as a defense of classical political economy in general and of Adam Smith in particular, focusing on misinterpretations of Smith’s work by the Younger Historical School in Germany. The essay reveals that Menger saw himself as working in a liberal tradition going back to Smith and classical political economy, rather than as a marginalist revolutionary who broke with classical political economy. It is a rare instance where Menger, holding the chair of economic theory at the University of Vienna, publicly expresses recommendations on economic policy. The essay represents Smith and the other classical political economists as socially motivated scholars concerned with just reforms to benefit ordinary people. Menger argues that the classical political economists were inclined toward liberal reforms but were by no means rigid exponents of laissez-faire. The essay is preceded here by an introduction authored by the translators Erwin Dekker and Stefan Kolev

Treatment recommendations for multimodality management of rectal cancer with a foc us on radiotherapy indications

Colorectal cancer (CRC) is one of the most commonly diagnosed cancer in Europe and US A and one of the leading causes of cancer death worldwide with 30% of all CRCs diagnosed in the rectum. Numerous published trials prove that the treatment of rectal cancer requires multidisciplinary approach. In this article the treatment recommendations for rectal cancer with an emphasis on radiotherapy (RT) application are defined

The role of radiotherapy in the contemporary multimodality management of rectal cancer

During the last 20 years the results of a significant number of trials concerning the multimodality management of rectal cancer have been published. This led to improvement of rectal cancer treatment. Radiotherapy (RT) is part of the standard multimodality treatment of rectal cancer and results in 50% local control improvement. The findings of the trials have answered some questions like the modalities sequencing, the combination of RT and chemotherapy, the RT fractionation regimens and the required total dose in addition to surgery either local or radical, the application of contact RT in early rectal cancer and intraoperative radiotherapy (IOR T) in locally advanced and recurrent rectal cancer. Neoadjuvant chemoradiation (CRT) followed by total mesorectal excision (TME) is the current standard treatment of patients with locally advanced rectal cancer with improved local control over postoperative CRT. In spite of the improved locoregional control, controversies exists and other opportunities for improvement are being investigated. In the present paper, the evidence behind the current standard of RT and the controversies in the treatment of patients with rectal cancer are reviewed

Morphological Changes in the Tissues Under The Action of Nd: YAG Laser in Peptic Ulcer Bleeding

The autors carry out a morphological study of 60 endoscopic biopsies of stomach mucosa followed-up consequencently in time. The study describes the morphological changes in the tissues under the action of Nd:YAG laser beam in cases of acute bleeding from peptic ulcers. Study proves that Nd:YAG LFC has lasting haemostatic and epithelising effect, i. e. it exerts a long-lasting therapeutic effect