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The paper presents a method for solving electromagnetic field problems by applying impedance boundary conditions for systems including conducting bodies of nonlinear magnetic properties in an excited harmonic field. Three types of impedance boundary conditions were derived. A procedure for computing surface impedance based on the transfer matrix is proposed. This procedure has been tested by comparing computational results to calculations where time function distortions were considered, and to the experimental data.

The article presents cost of equity estimation of capital groups from the fuel and energy sector, listed at the Warsaw Stock Exchange, based on the Capital Asset Pricing Model (CAPM). The objective of the article was to perform a valuation of equity with the application of CAPM, based on actual financial data and stock exchange data and to carry out a sensitivity analysis of such cost, depending on the financing structure of the entity. The objective of the article formulated in this manner has determined its’ structure. It focuses on presentation of substantive analyses related to the core of equity and methods of estimating its’ costs, with special attention given to the CAPM. In the practical section, estimation of cost was performed according to the CAPM methodology, based on the example of leading fuel and energy companies, such as Tauron GE and PGE. Simultaneously, sensitivity analysis of such cost was performed depending on the structure of financing the company’s operation.

An efficient method for simulating quantum transport in quantum cascade lasers is presented. The calculations are performed within a simple approximation inspired by Büttiker probes and based on a finite model for semiconductor superlattices. The formalism of non-equilibrium Green’s functions is applied to determine the selected transport parameters in a typical structure of a terahertz laser. Results were compared with those obtained for a infinite model as well as other methods described in literature.

Abstract Background Severe Clostridium difficile toxin-induced enteritis is characterized by exuberant intestinal tissue inflammation, epithelial disruption and diarrhea. Adenosine, through its action on the adenosine A2A receptor, prevents neutrophillic adhesion and oxidative burst and inhibits inflammatory cytokine production. Alanyl-glutamine enhances intestinal mucosal repair and decreases apoptosis of enterocytes. This study investigates the protection from enteritis by combination therapy with ATL 370, an adenosine A2A receptor agonist, and alanyl-glutamine in a rabbit and murine intestinal loop models of C. difficile toxin A-induced epithelial injury. Methods Toxin A with or without alanyl-glutamine was administered intraluminally to rabbit ileal or murine cecal loops. Animals were also given either PBS or ATL 370 parenterally. Ileal tissues were examined for secretion, histopathology, apoptosis, Cxcl1/KC and IL-10. Results ATL 370 decreased ileal secretion and histopathologic changes in loops treated with Toxin A. These effects were reversed by the A2A receptor antagonist, SCH 58261, in a dose-dependent manner. The combination of ATL 370 and alanyl-glutamine significantly further decreased ileal secretion, mucosal injury and apoptosis more than loops treated with either drug alone. ATL 370 and alanyl-glutamine also decreased intestinal tissue KC and IL-10. Conclusions Combination therapy with an adenosine A2A receptor agonist and alanyl-glutamine is effective in reversing C. difficile toxin A-induced epithelial injury, inflammation, secretion and apoptosis in animals and has therapeutic potential for the management of C. difficile infection.

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Dual antiplatelet therapy (DAPT) is mandatory after percutaneous coronary intervention (PCI) with drug-eluting stent (DES) implantation, but optimal DAPT duration remains a topic of intense discussion. The shorter regimen of DAPT might be especially beneficial for high-bleeding-risk (HBR) patients. Novel stent platforms have been designed with innovations that should facilitate vessel healing following stent implantation and enable short DAPT. This review aimed to summarize evidence of the neointimal coverage of short-term stents and their implications for DAPT duration. Results from histological and optical coherence tomography (OCT) studies confirm the significant role of uncovered struts after the implantation of a stent in patients presenting with late stent thrombosis. Several studies have shown favorable vessel healing at one month (with 83.2% of covered struts, on average) and three months following stent implantation (with 93.3% of covered struts, on average). Solely HBR patient trials have proven that one month of DAPT can be applicable and safe in this population. Three-month DAPT was tested in a more diverse population and remains effective and safe in comparison to a longer DAPT regimen. That evidence proves that short-term DAPT might be applicable, especially for HBR patients.

One of the critical parameters of thin-film electrically conductive structures in wearable electronics systems is their conductivity. In the process of using such structures, especially during bending, defects and microcracks appear that affect their electrical parameters. Understanding these phenomena in the case of thin layers made on flexible substrates, including textile ones, which are incorporated in sensors that monitor vital functions, is a key aspect when applying such solutions. Cracks and defects in such structures appearing during their use may be critical for the correct operation of such systems. In this study, the influence of defects resulting from the repeated bending of the conductive layer on its conductivity is analyzed. The anisotropic and partly stochastic characteristics of the defects are also taken into account. The defects are modeled in the form of broken lines, whose segments are generated in successive iterative steps, thus simulating the gradual wear of the layer material. The lengths and inclinations of these sections are determined randomly, which makes it possible to consider the irregularity of real defects of this type. It was found that near the percolation threshold, defects with a more irregular shape have a dominant effect on the reduction of conductivity due to the greater probability of their connection. The simulation results were compared with the experimental data. It was found that the dependence of the conductivity of the conductive layer on the number of bends is logarithmic. This allowed for the derivation of a formula linking the iteration number of the simulation procedure with the number of bends. Improving the strength of such layers is a technological challenge for researchers.

Numerical research into the QCL tunability aspects in respect to being applied in chemical substance detection systems is covered in this paper. The QCL tuning opportunities by varying power supply conditions and geometric dimensions of the active area have been considered. Two models for superlattice finite (FSML) and infinite (RSM) size were assumed for simulations. The results obtained have been correlated with the absorption map for selected chemical substances in order to identify the potential detection possibilities.

Modelling of quantum cascade laser (QCL) structures, despite a regular progress in the field, still remains a complex task in both analytical and numerical aspects. Computer simulations of such nanodevices require large operating memories and effective algorithms to be applied. Promisingly, by applying semi-analytical polynomial approximation method to computing potential, wave functions and electron charge distribution, accurate results and quick convergence of the self-consistent solution for the Schrödinger and Poisson equations are reachable. Additionally, such an approach makes the respective numerical models competitively effective. For contemporary QCL structures, with quantum wells quite typically forming complex systems, a special approach to determining self energies and coefficients of approximating polynomials is required. Under this paper we have analysed whether the polynomial approximation method can be successfully applied to solving the Schrödinger equation in QCL. A new algorithm for determining self energies has been proposed and a new method has been optimised for the researched structures. The developed solutions have been implemented as a new module for the finite model of the superlattice (FMSL) and tested on the QCL emitting light in the mid-infrared range.

We present the clinical case of a 63-year-old patient who underwent in the Department of Cardiac Surgery implantation of an aorto-bifemoral graft prosthesis and coronary artery bypass revascularization with application of less invasive off-pump technique. Graft selection (arterial grafts, venous grafts) is very important during qualification for coronary artery bypass revascularization. Minimally invasive saphenous vein harvesting was performed during the presented case. The endoscopic technique of vein harvesting is a relatively rarely applied technique during myocardial revascularization surgery. The concept of minimally invasive videoscopic technique is presented. There is a discussion on why the team decided to prolong duration of the case consisting of two major operations performed simultaneously. Minimally invasive videoscopic technique may have a significant positive impact on postoperative outcome in a selected group of patients.

Aim of Study: We analyzed the case of a patient treated in Vascular Surgery Department with the use of the hybrid procedure with a good results., Materials and Methods: Acute cases of dissected aortic aneurysm are commonly known as an immediate danger of human live and determinate a big challenge for physicians. The collaboration of classic and endovascular methods (hybrid procedures) gives much more chances to improve patient's survival and resumption to normal life activity. Endovascular procedures are limiting the operation shock, improving recovery time. That means rising the chances of survival so advanced surgical procedure., Conclusion: Hybrid procedures are a modern technic that gives good results.

The chronic lower limbs ischaemia is caused mainly by arteriosclerosis. After insufficient conservative treatment only the surgical intervention can salvage the limb. The revascularisation surgery can be performed by open surgery with implantation of the prosthetic bypass or by endovascular angioplasty with stent. This second method seems to be the best alternative for the patients with several concomitant systemic diseases. Nevertheless it is limited by presence of the long-distance arteriosclerotic lesions. The resolve of that problem is use of new generation of long endovascular covered stents. They can be succesfuly used in aorto-femoral and femoro-popliteal segment. Their efficiacy is simmilar to traditional prosthetic grafts.

The Purpose: Every foreign body injected into an organism causes an inflammatory condition. Among other things leukocytes take part in it. The healing of a vascular prosthesis means gradual subsiding of an inflammatory condition. The process can be monitored with the series of scintigraphy following decrease of an area of concentrating of Technetium-labeled leukocytes. The purpose of work was an appraisal of the healing of both types of prostheses in cases of patients operated because of aneurism of abdominal aorta., Material and Methods: In three years 64 patients have been examined. They were divided into two equal groups: I-patients after (stent-graft) being implanted because of abdominal aneurysm, II-patients after aortobifemoral prosthesis being implanted of the same reason. The scintigraphy was done in 3-4 day, in 3-, 6- and 12 after a surgery. A surface of concentrating of leucocytes was counted in a computer programme which allows manual marking of a contour. The results were put through a statistical processing., Results: During a period after surgery an intensified inflammatory condition has been stated in a group of patients operated in classic way. In both groups a decreasing of an inflammatory condition has been observed. After 12 months an area of concentrating of leucocytes took up to 10 percent of initial values., Conclusions: The decreasing of an area of concentrating of leucocytes was observed independently of a type of vascular prosthesis. The higher reaction was where the classic prostheses were used. The scintigraphy shows only a cellular part of an inflammatory answer and it cannot be an independent way of a monitoring of the healing of the prostheses.

There is a methods of surgical treatment of secondary enteroaortal fistula after infection of vascular prostheses with the use silver prosthesis and great omentum. Secondary enteroaortal fistula is the most serious complication followed infection of vascular prosthesis, with high risk of death rate regardless of different operative methods. Patients is operated and the dracon prosthesis was exchanged to arterial homograft, which is more resistant to infections or subclavio-femoral bypasses. Removing of intestinal fistula included resection of duodenum and gastroenterotomy or duodenorrhaphy. The modification of duodenal fistula provision relies on duodenorraphy and protection of that area and prosthesis with pediculated flap of gastrocolic omentum conducted retrocolicaly in retroperitoneum space. The retrocolical and retroperitoneal omentoplasty seems to be a practical modification of aorto-duodenal fistula treatment with useful protection of duodenal plastic.

Critical lower limb ischemia is a term used to define those patients with chronic ischemic pain at rest, ulcerations or limb necrosis caused by confirmed atherosclerotic lesions of the arteries. In this paper to evaluate of the clinical usefulness of silver coated prostheses in critical lower limb ischemia was presented. The use of the vascular artificial prostheses (dacron, dacron with velour, dacron albumin coated, polytetrafluoroethylene, dacron gentamicin/ryfampicin coated) in the critical ischemia limbs threatened is her contagion. In cases of potentially threatened a contagion is indicated the use of vascular prostheses about enlarged resistance on the contagion, e.g. the silver/collagen coated prosthesis. A foundation of the use of such prostheses are antibacterial proprieties of polyester fibers salts of the silver. An aim of many works is estimation of healing of the silver prostheses of grafted in lower limb at ill with the critical ischemia where infecting of the synthetic material is extremely probable. The healing of the silver prosthesis rated is most often at the use of the scintigraphy with Technetium 99. One attends that such research will make possible the estimation of the usefulness of the vascular silver prostheses in reconstructive operations in the vascular surgery, particularly in cases threatened with the infection of used synthetic material.

The authors present etiology, diagnosis and operative treatment of thoracoabdominal aneurysms based on their own experiences, especially in performing proximal anastomosis between vascular graft and aorta. The protheses are made of polytertafluoroethylene or dacron. They are impregnated with colagen or soaked with argentum or antibiotics. Spinal cord and visceral organ protection is described. The authors present also endovascular treatment of aorta. Internal chasis of vascular protheses (stentgrafts) is made of biologically neutral metal (like stainless stell, nitinol, other alloys). Its diameter is simmilar to abdominal or thoracic aorta dimension. The chasis is covered by material used also to produce classic vascular protheses (polytetrafluoroethylene, dacron). Thoracoabdominal aneurysms occur rarely, but they are the most difficult problem in vascular surgery. According to literature occurrence of aneurysms in this section value from 4% to 10%. Atherosclerotic process is a exciting cause of this type of aneurysms. According to modified Crawfords classification there are five basic types of thoracoabdominal aneurysms. For pioneer of thoracoabdominal aneurysms surgical treatment one should to recognize S. Etheredge, who in 1954 as a first performed human, aortal homograft implantation with using temporary by-pass. In 1973 E. S. Crawford proposed a new way of management depended on in situ anastomosis between arterial trunks with prosthesis, without use of temporary bypass. In Anglo-Saxon literature this technique gained descriptive qualification "clamp and sew". Using this method, thoracoabdominal aneurysms surgery stood himself decidedly shorter and safer for patients.

The abdominal aortic aneurysm is a dilatation of infrarenal part of aorta. Its ethiology is still unknown. An infection and congenital disorders of conjunctive tissue are regarded as the main risc factors. Other factors could be a perimural thrombus and elastin and colagen degradation. It's not proved that atheromatosis is a risc factor. The disease concerns mainly the old males. Not treated aneurysm grows until rupture. The aneurysms are usually asympthomatic. Majority of them are found incidentally. Ultrasonography and computed tomography are used to extended diagnosis. The open surgery or endovascular surgery are only possible ways of treatment. The aneurysm with diameter over 55 milimeters, sympthomatic or rupted is an indication for surgery. The aim of the open surgery is implantation of the vascular prosthesis into retroperitoneal space. Endovascular method consist in placement of stent-graft in the lumen of aneurysm through small incision in a peripherial vessel. Stent-graft consists of metal chassis covered by classic vascular prosthesis. This method still requires the long-term assessment.

The purpose of this study is to evaluate of the use of and silver-coated medical prosthesis in cases of the massive vascular graft infection. In this paper the use of silver-coated medical prosthesis (29 patients) of massive dacron graft infection in Departament of Vascular, General and Transplantation Surgery In Wroclaw University of Medicine In the years 1999-2004 is presented. For lack of tissue material and because of the exclusion of extraanatomic bypass application, in situ replacement was attempted using silver-coated dacron vascular prosthesis more resistant to infection. Before and after the surgery in all patients imaging studies were performed. Duplex-Doppler Ultrasound demonstrated perigraft fluid collections and the scintigraphy with use of Technetium-labeled leukocytes revealed vast migration to the infected prosthesis. The remission of the symptoms of infection was obtained. In the postoperative follow up no perigraft fluid collections were observed. In the most cases positive clinical effect was obtained, the scintigraphy of implanted graft revealed its infection. Because the scintigraphy disclosed Technetium-labeled leukocytes vast migration to the implanted graft, the application of silver coated medical prosthesis should be very cautious and limited to the critical states.

Unlabelled: There is growing experimental evidence that Chlamydia pneumoniae is a risk factor and contribute to the development of atherosclerosis of carotid artery. This process might cause stenosis of carotid artery and TIA or stroke., Aim: Aim of this study was to evaluate the frequency of Ch. pneumoniae infection in carotid artery stenosis patients and in control group-healthy artery from multiorgan donors., Material and Methods: From each of 84 patients undergoing carotid endarterectomy the samples were analyzed by nested PCR for Ch. pneumoniae DNA. Furthermore we determined DNA Ch. pneumoniae in carotid artery from 20 multiorgan donors., Results: In control group-healthy artery the PCR for Ch. pneumoniae was negative in all samples. Ch. pneumoniae was detected in 57 patients (67.85%) with symptomatic carotid artery stenosis, however in 27 patients (32.15%) the PCR test was negative., Conclusions: We did not observe infection of Ch. pneumoniae in healthy carotid artery-control group. We noted great frequency of infection in patients with stenosis of carotid artery. Patients with stenosis of carotid artery can be candidates to antibiotic therapy, which can slow down the progression of artery stenosis.

In order to study pathogenesis of vascular prosthesis healing process the following experiment was designed. 16 dogs underwent implantation of unilateral straight aorto-femoral teflon (PTFE, polytetrafluoroethylene) by-pass. After 6 months all dogs were killed, dissected and vascular prostheses with margin of adjacent aorta and femoral artery were collected for further study. Areas of proximal and distal anastomosis were examined immunohistochemically. Presence of coagulation factor VII, and C3 complement factor were studied. The obtained results were analyzed statistically by means of t-Student test. Factor VII as well C3 were found in areas of both proximal and distal anastomosis. Concentration of all two substances in proximal and distal anastomosis was compared. No statistically valid differences in factor VII concentration in proximal and distal anastomosis were found, whereas amounts of C3 factor as well as degree of extracellular matrix infiltration were markedly higher in distal anastomosis.

We present in this paper application of haemostatic device TachoComb onto bleeding after vascular anastomosis of dacron vascular prosthesis (branch of aortobifemoral or bypass aortofemoral) with common femoral artery in the groin. Hemorrhagic complications have influence onto clinical status of operated patients. Haemostatic TachoComb dressing was applied at 30 cases and results were compared to control group consist of 25 cases, in which gas compresses were applied. Mean loss blood in group I with the usage of TachoComb was statistical characteristic (p < 0.003) smallest than in group II. Also mean time of hemostasis was shortest than in group II (p < 0.01). We proved that use of TachoComb limits bleeding from suture line connecting artery with vascular prosthesis.

In this paper the methods with synthetic vascular prosthesis used in surgical treatment of the secondary aorto-intestinal fistula are presented. 10 cases of 22 patients treated in the years 1993-2003 for secondary aorto-intestinal fistulas as a complication of vascular prosthesis infection are analysed. In all patients the abdominal CT, scintigraphy with technetium 99m labeled leucocytes and endoscopy were performed. The patients underwent the operation of infected dacron prosthesis' replacement with silver/collagen coated prosthesis or extraanatomic bypass (subclavian to femoral). To close the intestinal fistula the duodenectomy with gastroenterostomy was performed or the duodenum was sutured and protected with the use of pedicled omentum. In 4 patients extraanatomic subclavian-femoral of polytetrafluoroethylene (PTFE) bypass was used. In these cases the intestinal surgery was composed of the partial duodenectomy with fistula excision and duodenal stumps formation followed by antecolic gastrojejunostomy with the Braun's enteroanastomosis and pyloroplasty. In this group 2 patients (50%) died in the follow up period. There were two extraanatomic bypass thromboses in the 30 days follow up and one amputation (25%). The infected vascular prosthesis was replaced with silver/collagen coated prosthesis in the 6 patients. In these cases duodenal fistula was closed with two layers of stitches and additionally protected with pedicled fragment of the greater omentum, which was sewn on the duodenum. In this group 1 patients (16.7%) died in the follow up period. In one case (16.7%) in 9 months after operation reinfection od silver prosthesis was observed. There were no significative differences (p = 0.45) in terms of early mortality between both group of patients. The treatment of the fistula is a difficult and hazardous surgical procedure, results of which are unpredictable.