Sol-gel hybrid films based on organosilane and montmorillonite for corrosion inhibition of AA2024.

The present work reports the production of films on AA2024-T3 composed of vinyltrimethoxysilane (VTMS)/tetraethylorthosilicate (TEOS) with incorporation of montmorillonite (sodium montmorillonite and montmorillonite modified with quaternary ammonium salt, abbreviated Na and 30B, respectively), generated by the sol-gel process. According to FT-IR analyses the incorporation of montmorillonite does not affect silica network. Electrochemical characterization was performed by electrochemical impedance spectroscopy measurement in 0.05 mol L(-1) NaCl solution. Results indicate that montmorillonite incorporation improves the corrosion protection compared to the non-modified system. Scanning electron microscopy micrographs reveal that high concentrations of montmorillonite provide agglomerations on the metallic surface, which is in detriment of the anticorrosive performance. The VTMS/TEOS/30B films with the lowest concentration (22 mg L(-1)) of embedded clay provide the highest corrosion protection.

Sensitive thermal transitions of nanoscale polymer samples using the bimetallic effect: application to ultra-thin polythiophene.

A sensitive nanocalorimetric technology based on microcantilever sensors is presented. The technology, which combines very short response times with very small sample consumption, uses the bimetallic effect to detect thermal transitions. Specifically, abrupt variations in the Young's modulus and the thermal expansion coefficient produced by temperature changes have been employed to detect thermodynamic transitions. The technology has been used to determine the glass transition of poly(3-thiophene methyl acetate), a soluble semiconducting polymer with different nanotechnological applications. The glass transition temperature determined using microcantilevers coated with ultra-thin films of mass = 10(-13) g is 5.2 °C higher than that obtained using a conventional differential scanning calorimeter for bulk powder samples of mass = 5 × 10(-3) g. Atomistic molecular dynamics simulations on models that represent the bulk powder and the ultra-thin films have been carried out to provide understanding and rationalization of this feature. Simulations indicate that the film-air interface plays a crucial role in films with very small thickness, affecting both the organization of the molecular chains and the response of the molecules against the temperature.

Structural versatility of oxalamide-based compounds: a computational study on the isomerization of the oxalamide group and the structural preferences of the polyoxalamides.

The conformational properties of the oxalamide group and crystal structure of several polyoxalamides have been investigated by computational methods. First, a detailed quantum mechanical study of the conformational preferences of N,N'-dimethyloxalamide is reported. Results, which were obtained at the MP2/6-31G(d) level, provide not only the minimum energy conformations but also a description of the energetics and structural changes associated to the isomerization process of the oxalamide group. These quantum mechanical results together with those obtained from additional calculations have been used to develop a set of force-field parameters for the oxalamide group. Molecular mechanics calculations have been performed to test the parameters and to provide new information in terms of energy contributions about the isomerization of the oxalamide group. On the other hand, the new set of parameters has been used to investigate the structural preferences of polyoxalamides (-[NH-CO-CO-NH-(CH(2))(n)]-) by PCSP calculations. Results indicated that polyoxalamides with an even number of methylene groups adopt a structure with one hydrogen bonding direction, whereas polymers with an odd number of methylene groups prefer a structure with two hydrogen bonding directions. The latter crystal structure is completely different from that observed in conventional polyamides and has been investigated in detail through Monte Carlo simulations.

Dimethyl N,N'-oxalamidodiethanoate.

The title compound, dimethyl 2,2'-(oxalyldiimino)diethanoate, C(8)H(12)N(2)O(6), exhibits a network of hydrogen bonds between amide and ester groups. Molecules lie on inversion centres and show a planar conformation for both the oxalamide and ester groups. The glycine residues adopt a conformation close to the polyglycine II structure.

[Anatomic reconstruction of native coronary arteries and vein graft with less shortening wallstent]. / Reconstrução anatômica das artérias coronárias nativas e das pontes de safena utilizando less shortening wallstent.

PURPOSE: To evaluate the advantage of the wallstent in the treatment of long or multiple lesions. METHODS: Thirty eight patients with mean age 66 years underwent wallstent implantation. Fourteen had lesions in the left anterior descending, 12 in the right coronary, nine in the circumflex and four in a vein graft. The technique for implantation requires an accurate quantification of the vessel diameter, because the chosen stent should be 1.5 mm larger than the target vessel. A new technique using additional inflations with high pressure balloons was applied. RESULTS: Successful implantation occurred in 95%. We did not have success in two patients. One of them due to damage in the stent and the other to unsuccessful liberation. Both patients were submitted to conventional angioplasty without complications. CONCLUSION: The wallstent implantation can be successfully performed with high success rate, but late angiographic results still demand further studies.

Reconstrução anatômica das artérias coronárias nativas e das pontes de safena utilizando Less Shortening Wallstent / Anatomic reconstruction of native coronary arteries and vein graft with the Less Shortening SelfÄExpandable Wallstent

OBJETIVO Ä Avaliar a utilizaçäo de apenas um stent, owallstent (WS), no tratamento de lesöes longas (LL) ou múltiplas (LM). MÉTODOS Ä Trinta e oito pacientes com idades variando de 42Ä82 (m=66) anos, sendo por cento do sexo masculino. Os vasos tratados foram: descendente anterior (14 pacientes); coronária direita (12); circunflexa (9) e pontes de safena (4). Cinco pacientes necessitaram de 2 stents: 4 PalmazÄSchatz no segmento proximal do vaso e um que recebeu dois WS com diâmetro maior ou igual a 1,5mm do diâmetro nominal do vaso.Todos os pacientes necessitaram de hiperinsuflação após o implante do WS. RESULTADOS - O sucesso do implante foi de 95 por cento. Os dois casos de insucesso foram: um devido à fratura do sistema e outro à soltura incompleta. Ambos, submetidos à angioplastia convencional com sucesso. Não houve complicaçöes nesta série. CONCLUSÄO - O WS foi efetivo no tratamento de LL e LM com alto índice de sucesso imediato e sem complicaçöes.

[Palmaz-Schatz coronary stent implantation in the protected left main coronary artery. Restenosis and repeat angioplasty using intravascular ultrasound as optimal deployment's factor]. / Implante de stent Palmaz-Schatz em tronco de coronária esquerda protegido. Reestenose e redilatação utilizando o ultra-som intracoronário como fator de otimização.

White woman 46 years old was admitted with oppressive rest angina. Two months prior, she had been submitted to a coronary artery bypass surgery: saphenous vein graft to the left anterior descending coronary; left internal mammary artery to the 1st diagonal branch and a radial artery as a free artery graft, to the biggest branch of the left circumflex artery. On coronary angiography, both the saphenous vein and the radial artery were occluded, with patency of the left internal mammary artery. The patient underwent coronary angioplasty with a Palmaz-Schatz stent 3.0/15 mm implantation in the left main coronary artery and was submitted to a high-pressure balloon inflation. She was discharged free of angina from the hospital and one month later retrosternal chest pain recurred. On coronary angiography a restenosis in the left main coronary was seen. Repeat coronary angioplasty with high-pressure balloon inflation technique and with intravascular ultrasound guidance was done. Larger balloons and progressive higher-pressure balloon inflations were used until reaching a stent internal lumen greater than the reference distal diameter. The patient was asymptomatic at four months of follow-up.

[Heterotopic heart transplantation. Initial clinical experience]. / Transplante cardíaco heterotópico. Experiência clínica inicial.

PURPOSE: To report our initial clinical experience with heterotopic heart transplantation, stressing its indications and a new modification in surgical technique. METHODS: We studied three patients underwent heterotopic heart transplantation, using an original technique in one of them. This new technique allows to connect both pulmonary arteries without any prosthetic tube. RESULTS: One early death and two late survivors, with 17 and 20 months of follow-up. One of them is clinically well and practices sports, regularly. CONCLUSION: Heterotopic heart transplantation could be considered as a good therapeutic option for end-stage patients with cardiomyopathy and right pulmonary vascular resistance, specially those with right ventricle. It can improve general results of heart transplantation because it reduces the early risks related to hemodynamic problems in a selected group of patients.

[Excimer laser in the treatment of obstructive coronary disease. Initial experience]. / Excimer laser no tratamento da doença coronária obstrutiva. Experiência inicial.

The aim of this study is to evaluate a group of four male patients aged between 47 and 77 years (mean 52 +/- 4.5) with coronary artery disease who underwent excimer laser with classical indication for this method. The vessels considered were the left anterior descending artery in three patients and the right coronary artery in one. Conventional percutaneous transluminal coronary angioplasty (PTCA) was applied in all patients after the laser procedure. Reduction to 50% or less of the internal diameter was considered a satisfactory result. Early success (laser plus PTCA) was obtained in 100%. There were a decreasing in number of obstruction from 75-100% (mean of 80 +/- 8.5%) to 0-50% (mean of 20 +/- 6%) after the procedure (laser plus PTCA). During hospitalization no complication have been found. In conclusion, we certified that excimer laser has been applied in special situation (complex lesions) with high rate of success than conventional angioplasty but these results will require further studies.

[The dilatation of the residual stenosis due to a Blalock-Taussig anastomosis by percutaneous transluminal angioplasty]. / Dilatação de estenose residual da anastomose Blalock-Taussig modificada pela angioplastia transluminal percutânea.

A ten-months-old white infant had undergone surgical modified Blalock-Taussig anastomosis at 2 months of age. An interposition of bovine mammary artery was anastomosed with the right subclavian artery. A satisfactory clinical follow-up after surgery was achieved, until the last three months when cyanotic spells were observed. A new angiographic study showed tricuspid and pulmonary atresia and severe stenosis (+/- 80%) at the anastomosis between the subclavian artery and the bovine mammary tissue. Percutaneous transluminal angioplasty was successfully performed. An immediate improvement of cyanosis and oxygen saturation were observed.

[Coronary angioplasty in octogenarians]. / Angioplastia coronária em octogenários.

PURPOSE: To evaluate the indications, results and follow-up of patients with 80 years old and over, who had undergone percutaneous transluminal coronary angioplasty (PTCA). METHODS: From July 1987 through July 1990, 36 patients, 80 years of age and over, had PTCA as an alternative method to treat coronary artery disease. Their age ranged from 80 to 85 (mean = 83) years. Twenty five were male. Significative obstruction was considered when 70% or more of the internal diameter was stenosed. Satisfactory results were achieved when reduction of 50% or more of the coronary artery obstruction was obtained. RESULTS: In 34 of 36 patients (94.4%), PTCA was successfully performed. Forty four of 46 coronary arteries were successfully dilated. One patient had acute coronary occlusion with acute myocardial infarction treated clinically. There were no emergency surgeries or early deaths. Clinical follow-up was obtained in 15 of the 34 patients. Four had repeated coronary arteriography (at 1, 3, 6 and 12 months after primary PTCA) due to angina. Two of them had restenosis and were successfully redilated (the patients restudied at 3 and 6 months, respectively). Within a mean clinical follow-up period of 9.6 (ranging from 1 from 21) months the following features were observed: two of 15 patients (13.3%) had acute myocardial infarction and were clinically followed; late death occurred in 3 patients (20%) with only one related to cardiac events. Survival has been observed in 12 of these 15 patients (80%). CONCLUSION: PTCA represents an alternative, safe and effective invasive procedure to treat octogenarians with coronary artery disease.

[Directional coronary atherectomy. The initial experience]. / Aterectomia coronária direcional. Experiência inicial.

Four male patients, 38 to 59 years old (mean 49 +/- 2.5), with angina and the angiographic features has been the classical indications for the method, underwent directional coronary atherectomy. Vessels treated were, respectively, left anterior descending artery (LAD), right coronary artery (RCA), saphenous vein graft (SVG) to LAD and SVG to left marginal branch. Reductions to 50% or less of the internal diameter was considered a satisfactory result. Early success was obtained in all four patients. Obstructions of 75 to 95% (mean of 83 +/- 7.5%) were reduced to 0-25% (mean 12 +/- 5%) after atherectomy. Only one patient died suddenly five days after de procedure. So, directional coronary atherectomy may represent a reliable and safe method for special situations.

[Anatomical limitations for the performance of angioplasty in coronary multivessel disease]. / Limites anatômicos para a realização de angioplastia na doença coronária multiarterial.

PURPOSE: To study anatomical limitation of coronary angioplasty, as alternative therapy in patients with multivessel disease and submitted to bypass surgery. METHODS: In 380 patients with multivessel disease and submitted to previous coronary bypass surgery, age ranged from 41 to 72 (average = 51) years, being 68% males. The following parameters were analyzed in the coronary arteriographies: anatomic aspects of the coronary arteries and distribution of the atherosclerotic stenosis. The patients were arranged in accordance to the criteria: complete revascularization, incomplete and no indication for coronary angioplasty. RESULTS: The patients were arranged in 3 different groups: I-80 (21%) patients included those in whom complete revascularization would be possible; II--55 (14.5%) patients in whom only incomplete revascularization but satisfactory would be possible and III--245 (65.5%) those patients in whom coronary angioplasty would no have indication. The data referind the patients of groups I and II were analyzed together--135 (35.5%) and arranged according to the number of arteries involved. It was observed: two vessel disease--71.8%, three vessel--18.6% and 4 or more vessel--9.6%. In group III it was observed 51.0% of the patients with 3 or more vessel disease. The major factors to contra indicate coronary angioplasty in group III included: chronic coronary obstruction 99 (40.4%); diffuse disease 11 (4.5%); technical difficulties 10 (4.1%); left main coronary artery obstruction 5 (2%) or when two or more causes were combined 120 (49%). CONCLUSIONS: Patients with multivessel disease and classic indication for coronary bypass surgery, have a basic limitation for angioplasty due to several anatomic factors. However, coronary angioplasty could be beneficial for a selected group of patients (35.5%) whenever a complete or incomplete revascularization could be obtained.

[Coronary angioplasty in young patients]. / Angioplastia coronária em pacientes jovens.

PURPOSE: To evaluate the results of coronary angioplasty in patients at the age of 40 years old or under. METHODS: From July 1987 to July 1990, 878 coronary angioplasty procedures were performed. Sixty six patients (7.5%) were 40 years old or under. The coronary obstruction was considered significant when 70% or more of the arterial diameter was involved and the post angioplasty results were considered satisfactory when residual obstruction was less than the 50%. RESULTS: Fifty four patients (81.8%) were male with an average age of 37 years (ranging from 29 to 40). Forty four patients (67%) had stable angina, 18 (27%) unstable angina, 3 (4%) acute myocardial infarction (AMI) and one (1.5%) AMI after streptokinase treatment. Eight of these patients had previous report of AMI and 3 (4.5%) had undergone coronary bypass grafting surgery. Fifty five patients (83%) had single vessel disease and 11 (17%) had multivessel disease. Eighty coronary arteries had balloon dilatation. In 32 patients (58%) with single vessel artery, 12 (22%) in the RCA, 10 (18%) in the left circumflex and one (2%) into a saphenous vein bypass grafting. In 12 patients (48%) with multivessel disease it was performed in the LAD coronary artery, 8 (32%) in the RCA and 5 (20%) in the left circumflex. Angioplasty was successfully performed in 53 (96%) patients with single vessel disease and in 10 (01%) with multivessel disease. One of the patients died immediately after the procedure. A follow up of 11.6 months (ranged from 1 to 27 months) was possible in 63 patients. Re-stenosis was depicted in 10 (19%) of the 55 patients with single vessel disease and in 3 of the 11 patients (30%) with multivessel disease. Nine patients had a successful redilatation in the first group and 2 in the second one. The two remaining patients had undergone coronary bypass surgery. The clinical evaluation among patients who had been dilated as the first procedure and those who had redilatation (61 patients) showed: 92% were asymptomatic and 8% had mild angina. CONCLUSION: Coronary angioplasty performed in young patients is an effective procedure with very low rate of early complications and favorable clinical follow-up.

[Coronary atherectomy using the transluminal endarterectomy extraction catheter. Initial experience]. / Aterectomia coronária com o uso do cateter de endarterectomia por extração transluminal. Experiência inicial.

PURPOSE: To describe a new alternative technique for treating coronary artery disease: the coronary atherectomy with the transluminal endarterectomy-extraction catheter. METHODS: Four patients, 1 female and 3 males age 46 to 65 years (mean 53 +/- 8.5 years), were submitted to coronary atherectomy with the transluminal endarterectomy-extraction catheter. One patient presenting stable angina, one presenting recent angina, one with residual stenosis after acute myocardial infarction treated with intravenous streptokinase and one with two episodes of syncope and ECG alterations. The treated arteries were: left anterior descending in 3 patients and left circumflex in one. Two lesion were concentric and two were segmentary and eccentric. RESULTS: The coronary artery stenosis ranged from 80 to 95% (mean of 90 +/- 7.1%) before the atherectomy and from 20-50% (mean of 32.5 +/- 12.6%) after the atherectomy. Except the first patient, the other 3 were discharged in less than 48 hours after the atherectomy. None presented chest pain during the procedure and in three of them were no recordings of dissection or coronary artery perforation. In one patient the treated artery presented total occlusion (thrombus) 15 minutes after the procedure, but was immediate and successfully reopened with balloon angioplasty. CONCLUSION: Coronary atherectomy with the "transluminal endarterectomy-extraction catheter" has shown to be a safe and feasible procedure and to bring satisfactory immediate results.

Thermographic study of laser on arteries.

We analyzed the different effects of CO2, Nd-YAG, and argon lasers on aorta by using a Thermovision infrared system that registered the laser interaction with mongrel dog aorta. The images (thermograms) obtained were processed by a computer, which associated each area of the same temperature with a determined color. These thermograms were compared to histological analysis of the respective samples and the following results were obtained: (1) After the application of each laser there is very little propagation of heat in tissue. (2) The CO2 laser makes tissue reach 100 degrees C in less than 0.05 seconds. (3) The heat dissipation time was higher with the Nd-YAG laser due to higher scattering on tissue. Based on this research we conclude that the CO2 laser was best absorbed, the Nd-YAG laser penetrated human tissue with the best results, and the argon laser had the most significant backscattering.