Development of FSW Process Parameters for Lap Joints Made of Thin 7075 Aluminum Alloy Sheets

The article describes machine learning using artificial neural networks (ANNs) to develop the parameters of the friction stir welding (FSW) process for three types of aluminum joints (EN AW 7075). The ANNs were built using a total of 608 experimental data. Two types of networks were built. The first one was used to classify good/bad joints with MLP 7-19-2 topology (one input layer with 7 neurons, one hidden layer with 19 neurons, and one output layer with 2 neurons), and the second one was used to regress the tensile load-bearing capacity with MLP 7-19-1 topology (one input layer with 7 neurons, one hidden layer with 19 neurons, and one output layer with 1 neuron). FSW parameters, such as rotational speed, welding speed, and joint and tool geometry, were used as input data for ANN training. The quality of the FSW joint was assessed in terms of microstructure and mechanical properties based on a case study. The usefulness of both trained neural networks has been demonstrated. The quality of the validation set for the regression network was approximately 93.6%, while the errors for the confusion matrix of the test set never exceeded 6%. Only 184 epochs were needed to train the regression network. The quality of the validation set was approximately 87.1%. Predictive maps were developed and presented in the work, allowing for the selection of optimal parameters of the FSW process for three types of joints.

Analysis of the Influence of External Wall Material Type on the Thermal Bridge at the Window-to-Wall Interface

BACKGROUND

Although many works focus on increasing the energy efficiency of buildings, there are still a number of problems that need to be solved, such as reducing heat losses at the window-to-wall interface, especially since the requirements for saving energy used for heating/cooling rooms are constantly increasing. This paper analyses the impact of the material parameters of the external wall and the window installation in the insulation layer on the size of thermal bridges around the window.

PURPOSE

The aim of the work is to demonstrate the benefits resulting from the correct installation of the window, the appropriate location of the window in relation to the face of the external wall, as well as the correct selection of construction materials.

METHODOLOGY

In order to show the improvement in the energy efficiency of buildings, an analysis of the heating/cooling energy consumption was carried out for the selected buildings. The thermal and humidity analyses were carried out using TRISCO program, while the economic analysis was performed using the Audytor OZC program.

RESULTS

It was found that the proposed system of window installation in the thermal insulation layer reduced the annual heating demand by at least 10% on average.

CONCLUSIONS

It has been shown that the method of window installation and the type of the wall structural materials are interrelated and therefore should be considered simultaneously. Their proper selection allows for a reduction in the amount of energy needed for heating and cooling buildings, and thus a reduction of heating/cooling costs, as well as limiting greenhouse gas emissions.

Analysis of Durability of Watertight Concretes Modified with the Addition of Fly Ash

The growing demand for watertight concrete structures is conducive to the development of research in this area, but their results are rarely published. In order to partially fill this gap, the authors of the publication present the results of research into the effect of fly ash addition on the watertightness of concrete. Prior to the tests, a recipe for a concrete mix with the addition of a sealing admixture modified with fly ash was developed. The following properties were analyzed: consistency of the concrete mix, air content in the concrete mix, compressive strength of concrete, depth of penetration of water under pressure, and frost resistance of concrete for F150 level. The work meets the expectations of the construction industry with respect to the production of concrete structures resistant not only to the penetration of water into concrete but also resistant to aggressive substances dissolved in water that accelerate the destruction of concrete and corrosion of reinforcement bars. Based on the test results, it was found that the addition of fly ash to the concrete mix enhances the positive impact of the applied sealing admixture, increasing the tightness of the concrete. It reduces the depth of penetration of water under pressure and therefore increases the frost resistance of concrete.

Analysis of the Effectiveness of Technological Lubricants with the Addition of Boric Acid in Sheet Metal Forming

One of the main problems during sheet metal forming is the reduction in coefficient of friction and separation of contact surfaces in order to eliminate buildups of the formed material on the forming tools. For this purpose, technological lubricants based on mineral or synthetic oils are usually used. Unfortunately, their removal from the drawn parts and their subsequent utilization pose many problems and are expensive. Environmentally benign lubricants based on vegetable oils with the addition of boric acid could be an effective alternative to lubricants based on mineral and synthetic oils; however, the solubility of boric acid in oils is limited. Therefore, the paper proposes new, effective, and environmentally friendly methods for applying boric acid to the metal sheet by spraying it on a thin rapeseed oil layer previously applied to the metal sheet or by spraying a 25% solution of boric acid in methyl alcohol onto the sheet. The effectiveness of such lubrication was assessed on the basis of the so-called strip drawing test, Erichsen cupping test, and formation of cylindrical drawn parts in industrial conditions. The tests showed that the addition of boric acid was most effective for forming the DC01 steel sheet, reducing the coefficient of friction by about 60% compared to base oil lubrication. Although its usefulness is lower in the case of other frictional pairs, it eliminates the phenomenon of the formed material sticking to the tool, thus extending the life of the forming tools. The use of the proposed solution reduces production costs and indirectly boosts environmental protection. Moreover, an explanation of the tribological mechanism contributing to the lubrication action of boric acid is given.

A New Method of Predicting the Parameters of the Rotational Friction Welding Process Based on the Determination of the Frictional Heat Transfer in Ti Grade 2/AA 5005 Joints

The article presents an original approach to determining the basic parameters of rotational friction welding (RFW) based on the analysis of friction heat transfer at the faying surfaces. Dissimilar Ti Grade 2/AA 5005 joints were used to demonstrate the method. The work established that for the analyzed joint, the optimum temperature at the faying surface that allow for a good quality weld to be obtained should be ~505 °C. On this basis, a map of optimal parameters was developed to achieve this temperature. This approach could potentially allow for more precise control of the welding process, leading to better joint quality and performance. The paper includes both a description of the technological process of friction welding and an attempt to explain the mechanism of the phenomena occurring in the welding area. The numerical calculations presented in the article were carried out using the ADINA System v. 9.8.2, which allows for the consideration of heat friction in the axial symmetric thermo-mechanical model. Frictional resistance was determined by the temperature-dependent friction coefficient. The assumed thermo-mechanical model required the determination of elastic-plastic properties versus temperature for the analyzed materials. The simulations of the friction welding were carried out for the different welding parameters and time. The different variants of friction welding were modelled.

Tribological Aspects of Sheet Titanium Forming

Friction, wear, and lubrication are inherent to all metal-forming processes. Unfortunately, they are particularly troublesome when forming titanium materials, which tend to form titanium buildup on the working surfaces of the forming tools. Lubrication is one of the most effective ways to separate contacting surfaces and eliminate galling, thus reducing tool wear. The paper presents the tribological aspects of titanium sheets forming using environmentally friendly lubricants with the addition of boric acid. The lubricant's effectiveness was assessed on the basis of technological tests, such as the strip drawing test, the Erichsen cupping test, and the formation of spherical drawn parts in industrial conditions. Moreover, the results of the numerical simulation of forming a titanium hat-shaped part are presented. Numerical calculations of forming processes were performed using the PamStamp 2G system based on the finite element method. Both experiments and numerical analyses showed the positive effect of lubricants with boric acid on sheet titanium forming.

Numerical and Experimental Analysis of Titanium Sheet Forming for Medical Instrument Parts

The paper analyses the forming of the surgical instrument handles made of Grade 2 titanium sheets. Sheet metal forming is a technology ensuring high strength and light weight of products. Replacing stainless steels with titanium further reduces instrument weight and additionally provides the required resistance to corrosive environments typical for surgeries. The low instrument weight is important to prevent fatigue of surgeons and allow them to maintain high operational accuracy during long term surgeries. The numerical analysis of the technological process was performed in order to adapt it to forming tool handles using titanium sheets instead of steel sheets. The numerical calculations were experimentally verified. It was found that, in the case of titanium handles, it is necessary to use a blank holder in the first forming operation to eliminate sheet wrinkling in the flange area. The shape and dimensional accuracy of the drawn part after trimming were high enough and the 4th forming operation became unnecessary. Moreover, the process modification included lubrication using rapeseed oil with the addition of boric acid, which effectively prevents the galling of titanium on the working surfaces of the steel tools and ensures a more uniform distribution of plastic strains in the drawn part.

Stage I Melanoma of the Limbs. Immediate versus Delayed Node Dissection

553 patients with stage I malignant melanoma of the limbs entered a prospective randomized clinical trial carried out by the W.H.O. Collaborating Centres for Evaluation of Methods of Diagnosis and Treatment of Melanoma from September 1967 to January 1974. 286 patients were submitted to wide excision of primary and node dissection at the time as appearance of regional lymph node metastases and 267 to wide excision and immediate node dissection. Survival was identical in the 2 groups. Different subsets of patients were evaluated to assess whether some groups of patients may benefit from immediate node dissection. As regards sex, females and a significantly higher survival rate than males (p < 0.05), but results were not improved by immediate node dissection. Maximum diameter and elevation of primary melanoma were significantly related to survival but also in these cases immediate node dissection did not achieve better results. 63 patients had an excisional biopsy of their melanoma within 4 weeks before final treatment. This procedure did not worsen survival and also in this case immediate node dissection did not improve survival. 273 cases were classified according to histologic type: survival of superficial spreading and nodular melanoma was not different at a statistically significant level after the 2 treatment modalities. 325 cases were considered classifiable according to Clark's levels, out of these 165 were submitted to immediate node dissection. Neither level III nor level IV cases showed higher survival rate after immediate node dissection. Maximum tumor thickness according to Breslow was evaluated in 338 cases: 188 were submitted to wide excision and immediate node dissection. In no clusters of thickness did the enlarged surgical procedure achieve better results. The authors conclude that there is good evidence that in stage I melanoma of the extremities delayed dissection is as effective as the immediate one in the control of the disease if the patient can be kept under strict clinical control. Immediate node dissection is advisable if the quarterly follow-up is not guaranteed, at least for melanomas thicker than 2 mm.

1-Methylnicotinamide (MNA), a primary metabolite of nicotinamide, exerts anti-thrombotic activity mediated by a cyclooxygenase-2/prostacyclin pathway

BACKGROUND AND PURPOSE

1-methylnicotinamide (MNA) has been considered to be an inactive metabolite of nicotinamide. Here we assessed the anti-thrombotic activity of MNA in vivo.

EXPERIMENTAL APPROACH

Antithrombotic action of MNA was studied in normotensive rats with extracorporeal thrombus formation (thrombolysis), in renovascular hypertensive rats with intraarterial thrombus formation (arterial thrombosis) and in a venous thrombosis model in rats (venous thrombosis).

KEY RESULTS

MNA (3-100 mg kg(-1)) induced a dose-dependent and sustained thrombolytic response, associated with a rise in 6-keto-PGF(1alpha) in blood. Various compounds structurally related to MNA were either inactive or weaker thrombolytics. Rofecoxib (0.01-1 mg kg(-1)), dose-dependently inhibited the thrombolytic response of MNA, indomethacin (5 mg kg(-1)) abolished it, while L-NAME (5 mg kg(-1)) were without effect. MNA (3-30 mg kg(-1)) also reduced arterial thrombosis and this effect was abrogated by indomethacin (2.5 mg kg(-1)) as well as by rofecoxib (1 mg kg(-1)). MNA, however, did not affect venous thrombosis. In vitro MNA did not modify platelet aggregation nor induce vasodilation.

CONCLUSIONS AND IMPLICATIONS

MNA displayed a profile of anti-thrombotic activity in vivo that surpasses that of closely related compounds. MNA inhibited platelet-dependent thrombosis by a mechanism involving cyclooxygenase-2 and prostacyclin. Our findings suggest that endogenous MNA, produced in the liver by nicotinamide N-methyltransferase, could be an endogenous activator of prostacyclin production and thus may regulate thrombotic as well as inflammatory processes in the cardiovascular system.

In search for new antipsoriatic agents: NAD topical composition

The aim of the study was to examine the effectiveness of the oxidized form of nicotinamide adenine dinucleotide (NAD(+)), adenosine precursor, in 37 patients suffering from psoriasis. As NAD(+) is known to be relatively unstable, the second goal was to establish the proper conditions for the satisfactory stability of topical NAD(+) composition. In each patient, two matching plaques were selected for the study. Topical treatment with 1 or 0.3% NAD(+) in Vaseline ointment administered twice daily was compared with overnight therapy with 0.1% anthralin applied for 12 h and placebo. The enzymatic method was applied to determine the stability of NAD(+) in Vaseline ointment. After a 4-week application, the reduction in erythema, infiltration and desquamation caused by 1 or 0.3% topical NAD(+) composition was similar to the reduction caused by 0.1% anthralin. It was demonstrated that NAD(+) underwent a considerable decomposition at room temperature, while it was sufficiently stable at 5 degrees C; thus, for a longer use the agent should be stored at fridge temperature. NAD(+) therapy combines good efficacy, cosmetic acceptability and convenient twice-daily application.

Topical application of NADH for the treatment of rosacea and contact dermatitis

Among many important physiological functions played by NADH (the reduced form of beta-nicotinamide adenine dinucleotide) its antioxidative properties are remarkable. Acting directly as an antioxidant, NADH can effectively protect the cell and its membrane from destruction by free radicals. NADH can be stabilized as a suspension in hydrophobic ointments prepared in a way that prevents contact with atmosphere containing oxygen and water. We present the first report of NADH as a treatment for some inflammatory dermatoses. It was found that topical application of 1% NADH diluted in Vaseline ointment can be very effective in the treatment of rosacea and contact dermatitis. Since no adverse effects were observed, therapy with NADH can be viewed as a potential alternative to other established treatments.

Passive-fixation J-shaped versus straight leads in atrial position: comparison of efficacy and safety

To compare the efficacy and safety of straight and J-shaped passive-fixation atrial leads we retrospectively analyzed the results of 100 consecutive implantations of atrial leads at one institution. There were seven cases of upgrades of VVIR to DDDR systems and in one case an active-fixation lead was chosen as a primary approach. These eight patients were excluded from the analysis. The final study group consisted of 92 cases (69 DDDR, 23 AAIR), 69 were J and 23 straight leads. The stimulation threshold, slew rate, impedance, P wave amplitude, and procedural time did not differ significantly between the two types of leads used. During the long-term follow-up of 6-53 months (30 +/- 11.9 months), replacements using active-fixation leads were required in two patients with straight leads and three patients with J leads (P = NS). In addition, one J lead showed signs of damage (impedance > 3,000 Ohm). Long-term follow-up values of the stimulation thresholds and P wave amplitudes did not differ between the groups (P = NS). Transesophageal echocardiography performed in 13 patients revealed a trend toward more distal placement of straight leads within the right atrial appendage. In conclusion, J-shaped leads do not seem to be superior to the straight leads for atrial implantations.

The terminal portion of the T wave: a new electrocardiographic marker of risk of ventricular arrhythmias

Experimental studies have shown that transmural dispersion of repolarization (DoR), defined as the difference in action potential duration between mid-myocardial M-cells, epicardial, and endocardial cells is reflected in the duration of the terminal portion of the T wave (TpTe) on the surface ECG. Since DoR is an important factor associated with the propensity for reentrant arrhythmias, this study examined if TpTe may serve as a marker of risk of ventricular arrhythmias. Data from 18 patients with coronary artery disease and inducible sustained ventricular tachycardia (VT group) were compared with those of 16 survivors of myocardial infarction without inducible VT (control group). TpTe was automatically measured in each beat of 24-hour ECG recordings, and programmed ventricular stimulation was performed in the antiarrhythmic drug-free state. TpTe was expressed as the absolute interval in milliseconds, and relative to the duration of QTe (TpTe/QTe x 100%). TpTe duration was 74 +/- 14 ms in the VT group versus 63 +/- 16 ms in the control group (P < 0.004). The TpTe interval expressed as a percent of the QT interval was 21 +/- 4% in the VT group versus 17 +/- 3% in the control group (P = 0.02). In patients with coronary artery disease. TpTe was longer in patients with, versus without, inducible VT. The results of this study support the hypothesis that TpTe reflects transmural dispersion of repolarization.

[Fibrinogen serum levels in patients with stable coronary artery disease and acute coronary syndrome]

Increased plasma fibrinogen level is an important prognostic factor of recurrent unstable angina and myocardial infarction in patients with acute coronary syndrome (ACS). The aim of our study was to assess the plasma fibrinogen level at baseline condition in patients admitted to hospital due to coronary artery disease (CAD). Plasma fibrinogen was measured in 51 consecutive patients presenting with ACS within the last 24 hours and in 50 patients with angiographically proven CAD that was stable for the past 30 days. For statistical analysis Mann-Whitney U test, Student t-test, chi-square test and Pearson correlation was used, p < 0.05 being considered statistically significant. There was significant correlation between fibrinogen level and diagnosis of ACS or CAD (r = 0.29, p = 0.002). In our population plasma fibrinogen levels (g/L +/- SD) were significantly different in patients with ACS when compared to CAD subjects (3.87 +/- 1.2 vs. 3.26 +/- 0.65, p = 0.002). There was difference between ACS and CAD subjects in male:female ratio (40/11 vs. 47/4, p < 0.001) and age (63.4 +/- 10.1 vs. 58.4 +/- 10.0, p = 0.014). Our results confirm the role of fibrinogen in pathogenesis of CAD. In our opinion plasma fibrinogen level may be an important diagnostic tool in assessment of patients with chest pain.

The radical cation of syn-tricyclooctadiene and its rearrangement products

The syn dimer of cyclobutadiene (tricyclo[4.2.0.0(2.5)]octa-3,7-diene, TOD) is subjected to ionization under different conditions and the resulting species are probed by optical and ESR spectroscopy. By means of quantum chemical modelling of the potential energy surfaces and the optical spectra, it is possible to assign the different products that arise spontaneously after ionization or after subsequent warming or illumination of the samples. Based on these findings, we propose a mechanistic scheme which involves a partitioning of the incipient radical cation of TOD between two electronic states. These two states engage in (near) activation-less decay to the more stable valence isomers, cyclooctatetraene (COT*+) and a bis-cyclobutenylium radical cation BCB*+. The latter product undergoes further rearrangement, first to tetracyclo[4.2.0.0(2,4).0(3,5]oct-7-ene (TCO*+) and eventually to bicyclo[4.2.0]octa-2,4,7-triene (BOT*+) which can also be generated photochemically from BCB*+ or TCO*+. The surprising departure of syn-TOD*+ from the least-motion reaction path leading to BOT*+ can be traced to strong vibronic interactions (second-order Jahn-Teller effects) which prevail in both possible ground states of syn-TOD*+. Such effects seem to be more important in determining the intramolecular reactivity of radical cations than orbital or state symmetry rules.

[Permanent heart pacing in treatment of cardioinhibitory vasovagal syncope (case report)]

Vasovagal syncope is a complex syndrome in which specific methods of treatment rarely are related to clinical success. Since it turned out that some patients with neurocardiogenic syncope were resistant to offered pharmacotherapy, cardiac pacing has been used as the alternative way of long-term therapy. Successive studies, which have estimated clinical efficacy of permanent cardiac pacing, indicate that such method of treatment may reduce symptoms revealed by vasovagal reflex. Nevertheless the optimal pacing mode has not been established yet. It is known that single chamber VVI pacing is not a good and effective method whereas dual chamber DDI pacing with rate hysteresis seems to be very promising in treatment of people suffering from malignant cardioinhibitory vasovagal syncope. DDD pacing with rate drop response, search and scan functions recently has been available to these patients. The results of the North American Vasovagal Pacemaker Study, as well as some casuistic observations referring to patients with vasovagal syndrome, show very high clinical efficacy of dual chamber pacing with mentioned new functions. We present a case of patient with cardioinhibitory vasovagal syncope who was successfully treated by permanent DDD pacing with search and scan hysteresis.

Perindopril for elderly people with chronic heart failure: the PEP-CHF study. The PEP investigators

BACKGROUND

The prevalence of chronic heart failure (CHF) rises with increasing age, from < 1% in those below 65 years of age to > 5% in those over 65 years of age and is a major cause of morbidity and mortality in older people. Recent European guidelines point to a major deficiency in our knowledge of how to treat diastolic chronic heart failure, and a lack of information on treatment for heart failure in the elderly in general.

AIMS

The aims of this trial are to assess the potential benefits of the ACE inhibitor perindopril to treat chronic heart failure in elderly people, in the absence of any major left ventricular systolic dysfunction.

SUBJECTS

One thousand people over the age of 70 years will be recruited into this study. Evidence of chronic heart failure will be confirmed by clinical criteria and echocardiography.

METHODS

Once a diagnosis of chronic heart failure has been confirmed, the patient will receive either perindopril or placebo in addition to their usual treatment. Death, and unplanned heart failure related hospitalisations, are the primary outcomes. Quality of life, as measured by the Guyatt questionnaire will be assessed at the beginning of the study and at 1 year. Sub-studies of this trial include a 6-min walking test and more detailed evaluation of ventricular function (as assessed by echocardiography). Both parameters will be measured at 8 weeks and 1 year, and analysed against baseline data. Cognitive function in this group of patients will also be evaluated at baseline and 1 year. This trial is due to report in the year 2001.

Antiviral activity of 1,7-disulphoanthraquinone

The antiviral activity of 1,7-disulphoanthraquinone (DSA) against hepatitis B viruses was investigated by measuring the titer of HBV surface antigen in the treated serum obtained from the blood of patients with acute infection. The presence of HBsAg was tested by the Vitek Immuno Diagnostic Assay System (VIDAS). The concentration of DSA in the samples was equal to 0.01, 0.1 and 1%, respectively. The results presented clearly showed an extensive disintegration of the virus envelope at elevated temperatures, which resulted in a substantial decrease in the concentration of HBsAg in the serum containing DSA. The concentration of HBsAg decreased also upon UV irradiation of the serum containing DSA in a photochemical reactor for 5 to 15 min, but the effect of degradation was not complete.

Effects of amiodarone on the P-wave triggered signal-averaged electrocardiogram in patients with paroxysmal atrial fibrillation and coronary artery disease

The effects of a 6-week treatment with amiodarone on the P-wave triggered signal-averaged electrocardiogram in patients with paroxysmal atrial fibrillation and coronary artery disease have been studied. Amiodarone favorably influences P-wave triggered signal-averaged electrocardiographic parameters, predominantly in patients in whom amiodarone is effective in preventing paroxysmal atrial fibrillation.

[The improvement of echocardiographic assessment of the left ventricle by the use of perflenapent and harmonic imaging]

Contrast echocardiography and harmonic imaging (HI) are promising new modalities applied in order to obtain improved visualisation of the left ventricle. Perflenapent (EchoGen, Abbott) is a new generation echocardiographic contrast agent that crosses the pulmonary capillary bed and produces long-term ventricle opacification. Our aim was to assess the left ventricle endocardial visualisation after perflenapent infusion and HI technique. We studied a pilot group of 10 patients (mean age 52.5 +/- 7.6, mean weight 76.9 +/- 10.1 kg, one female) with previously obtained sub-optimal non-contrast echocardiograms. Perflenapent was injected intravenously at dosis 0.05 ml/kg. Echocardiography was performed before perflenapent injection and during the time between injection and LV image disappearance. Images were assessed using four-point scale, 0 standing for the poorest and 3 for excellent visualisation. Perflenapent produced full chamber opacification in all pts. Contrast effect was observed for 550-15824 sec and myocardial enhancement was seen for 176-2116 sec after i.v. administration. After perflenapent administration, endocardial border was significantly better visible than before (1.9 +/- 0.57 vs. 2.9 +/- 0.31, p < 0.001). No hemodynamic effects were noted, as assessed by oxygen saturation, blood pleasure and heart rate. A mild, transient somnolence was seen in one pt. Perflenapent improved left ventricular function diagnostic capabilities, and provided enhanced visualisation of the myocardium.

Three-dimensional echocardiographic evaluation of left ventricular volume: comparison of Doppler myocardial imaging and standard gray-scale imaging with cineventriculography--an in vitro and in vivo study

BACKGROUND

Standard gray-scale imaging (GSI), three-dimensional (3D) echocardiography has been shown to be superior to two-dimensional echocardiography in measuring left ventricular volume. However, the often relatively poor quality of transthoracic gray-scale data can limit the potential application of this technique. Doppler myocardial imaging (DMI) is a new ultrasound technique that potentially offers higher-quality 3D images with a transthoracic approach than the 3D GSI technique. This study was designed to compare the accuracy of standard GSI and DMI 3D left ventricular volume measurements in vitro and in vivo.

METHODS AND RESULTS

In vitro, the minimum and maximum volume of the contracting single-chamber, tissue-mimicking phantom was calculated by using both techniques. In vivo, GSI and DMI 3D left ventricular volume measurements were performed in 16 patients. End-diastolic and end-systolic left ventricular volumes were computed for both techniques and compared with those calculated by cineventriculography. In vitro, both methods tended to underestimate the true phantom volume, but the systematic error was smaller for DMI than for GSI (-1.2% +/- 1.5% vs. -4.3% +/- 3%; p < 0.01) and was more constant in the case of DMI over the range of different sizes of true volume. In vivo, for GSI the end-diastolic volume mean difference was -12.6 ml and the limits of agreement were +/-18 ml, and for DMI the corresponding values were -4.2 and +/- 10.6 ml, respectively. The difference for end-systole was -6.5 +/- 10.6 ml and -1.5 +/- 10 ml for GSI and DMI, respectively. The magnitude of the difference in volume measurement between 3D echocardiography and cineventriculography was significantly smaller when using the Doppler technique.

CONCLUSIONS

The results of this in vitro and in vivo study indicate that DMI is superior to GSI as a transthoracic acquisition technique for 3 D volume computation.

[The significance of scintigraphic, echocardiographic and electrocardiographic left atrial transesophageal pacing in diagnosis of ischemic heart disease]

The aim of the study was to compare the perfusion scintigraphy (using SPECT method with Tc-99-MIBI) during left atrial transoesophageal pacing test (LAPT) with pacing electrocardiography (ECG), echocardiography (ECHO) and electrocardiography exercise test (ExT) in ischaemic heart disease (IHD) diagnostics. The effect of LATP on heart haemodynamic parameters and the correlation between scintigraphic, echocardiographic and electrocardiographic parameters during LAPT test have been also assessed. Investigations were carried out in 55 subjects (Group I: 36 patients with effort angina pectoris; group II: controls: 19 clinically healthy subjects). Coronarography was performed in 24 patients 6 weeks before or after examinations. LATP test was analyzed with ECG, ECHO and SPECT. Echocardiography did not increase significantly the LATP test diagnostic value. Perfusion scintigraphy enhanced sensitivity and predictive excluding value LATP test. These values were 93.3% v 62.9% and 90% v 59.3% respectively. LATP test assessed with ECG, ECHO and perfusion scintigraphy expressed significantly higher sensitivity and predicting excluding value in comparison to ExT. LATP test analyzed in such way was characterized by 100% sensitivity and 100% predicting excluding value.

CONCLUSION

Combination of LATP with electrocardiography, echocardiography and SPECT is a non-invasive high quality method for ischaemic heart disease diagnostics.

QT dispersion magnitude is related to the respiratory phase in healthy subjects

Twelve-lead electrocardiograms in 20 healthy volunteers during quiet respiration, maximum inspiration, and maximum expiration were recorded. QT dispersion was statistically significantly shorter both at maximum inspiration and maximum expiration than during quiet breathing.

Assessment of wall velocity gradient imaging using a test phantom

A new phantom has been designed to gain a better understanding of tissue Doppler imaging (TDI). Specifically, the phantom can easily be used to determine myocardial velocity gradients. The phantom mimics the left ventricle and is made of fine-grade sponge material whose ultrasound image closely resembles the gray scale image obtained from heart walls. Theoretical analysis of phantom wall movements offers a plausible explanation for the velocity gradients developing across the heart walls. The results of computer analysis were found to be in very good agreement with TDI M-mode recordings of phantom wall displacement.

Fibres in Lower Silesia hard coal mines respirable dusts

The paper describes the presence of fibres in respirable coal dust in high rank coal mines in Lower Silesia. The amount of fibres in dust particles is about 1.5% (by count). Testing by the incineration test, the lack of atomic number contrast in electron back-scattering imaging in SEM and X-ray microanalysis allow the fibres to be identified as coal. The authors suggest the possible role of coal fibres in the increased fibrogenic activity of the dusts in coal mines in Lower Silesia.

Thin stage I primary cutaneous malignant melanoma. Comparison of excision with margins of 1 or 3 cm

Although wide surgical excision is the accepted treatment for thin malignant melanomas, there is reason to believe that narrower margins may be adequate. We conducted a randomized prospective study to assess the efficacy of narrow excision (excision with 1-cm margins) for primary melanomas no thicker than 2 mm. Narrow excision was performed in 305 patients, and wide excision (margins of 3 cm or more) was performed in 307 patients. The major prognostic criteria were well balanced in the two groups. The mean thickness of melanomas was 0.99 mm in the narrow-excision group and 1.02 mm in the wide-excision group. The subsequent development of metastatic disease involving regional nodes and distant organs was not different in the two groups (4.6 and 2.3 percent, respectively, in the narrow-excision group, as compared with 6.5 and 2.6 percent in the wide-excision group). Disease-free survival rates and overall survival rates (mean follow-up period, 55 months) were also similar in the two groups. Only three patients had a local recurrence as a first relapse. All had undergone narrow excision, and each had a primary melanoma with a thickness of 1 mm or more. The absence of local recurrence in the group of patients with a primary melanoma thinner than 1 mm and the very low rate of local recurrences indicate that narrow excision is a safe and effective procedure for such patients.

Relations between visceral and behavioral function in men at bedrest

Multiple physiological measurements as well as a self-assessment of arousal was made in eight men on the first, third, and fifth days of bedrest. On the third day, additional measurements of performance on memory and dexterity tasks were made. Univariate analysis did not reveal any physiological variable to either predict subsequent performance well or to co-vary acutely with it; however, self-rating scores did prove to be useful predictors of subsequent performance. Principal components analysis suggested an "alertness" factor comprised of physiological measures as well as self-ratings which helped in predicting better performance. Although the individual patterns of correlations between variable on each of the three test days was variable, even more variability between subjects was found on the performance testing day. We believe this effect of behavioral activation may be due to the injection of common, slow temporal trends into many of the different data sets.

A randomized trial of adjuvant chemotherapy and immunotherapy in cutaneous melanoma

In a randomized trial of adjuvant chemotherapy, immunotherapy, or immunochemotherapy, 761 evaluable patients with pathological Stage II cutaneous melanoma anywhere on the body or with pathological Stage I melanoma of the trunk (Clark's level 3 to 5) were studied by the World Health Organization International Melanoma Group. Wide local excision and excisional regional lymphadenectomy alone were performed in 185 patients and the results were compared with those of surgery plus chemotherapy with dacarbazine (in 192 patients), surgery plus immunotherapy with bacille Calmette-Guérin vaccine (in 203), and surgery plus chemotherapy combined with immunotherapy (in 181). The rates of disease-free survival and overall survival at 36 months were 30.4 +/- 8.3 per cent (mean +/- S.E.) and 41.6 +/- 10.0 per cent, respectively, after surgical treatment alone; 37.2 +/- 7.9 per cent and 46.5 +/- 8.3 per cent after surgery plus chemotherapy; 34.8 +/- 7.9 per cent and 48.7 +/- 8.7 per cent after surgery plus immunotherapy; and 33.6 +/- 7.9 per cent and 50.0 +/- 8.8 per cent after surgery plus a combination of chemotherapy and immunotherapy. None of the differences between groups was significant, and thus no effect of adjuvant therapy could be demonstrated in this study.

Delayed regional lymph node dissection in stage I melanoma of the skin of the lower extremities

Results of a prospective randomized clinical trial conducted by the WHO Collaborating Centers for the Evaluation of Methods of Diagnosis and Treatment of Melanoma are reported. Five-hundred-fifty-three Stage I patients whose limbs were affected entered the study; 267 were submitted to wide excision and immediate node dissection and 286 had wide excision and node dissection at the time clinically positive nodes were detected. Survival curves of the two treatment groups could be superimposed. No subsets of patients benefitted from immediate node dissection. The authors conclude that delayed node dissection is as effective as the immediate dissection in Stage I melanoma of the extremities if the patient can be checked every three months. If the quarterly follow-up is not guaranteed, immediate node dissection is advisable, at least for melanomas thicker than 2 mm.