Consolidation and Forced Elasticity in Double-Network Hydrogels.

This paper discusses two observations that are unique with respect to the mechanics of double network (DN) hydrogels, forced elasticity driven by water diffusion and consolidation, which are analogous to the so-called Gough-Joule effects in rubbers. A series of DN hydrogels were synthesized from 2-acrylamido-2-methylpropane sulfuric acid (AMPS), 3-sulfopropyl acrylate potassium salt (SAPS) and acrylamide (AAm). Drying of AMPS/AAm DN hydrogels was monitored by extending the gel specimens to different stretch ratios and holding them until all the water evaporated. At high extension ratios, the gels underwent plastic deformation. Water diffusion measurements performed on AMPS/AAm DN hydrogels that were dried at different stretch ratios indicated that the diffusion mechanism deviated from Fickian behavior at extension ratios greater than two. Study of the mechanical behavior of AMPS/AAm and SAPS/AAm DN hydrogels during tensile and confined compression tests showed that despite their large water content, DN hydrogels can retain water during large-strain tensile or compression deformations.

Fabrication of Tough Double-Network Hydrogels from Highly Cross-Linked Brittle Neutral Networks Using Alkaline Hydrolysis.

This paper describes a simple method to synthesize tough hydrogels from a highly cross-linked neutral network. It was found that applying alkaline hydrolysis to a highly cross-linked hydrogel synthesized from acrylamide (AAm) can increase its swelling ratio dramatically. Double-network (DN) hydrogels synthesized from polymerization of loosely cross-linked AAm networks inside a highly cross-linked AAm gel were not tough. However, repeating the same recipes with a second polymerization step to synthesize a DN hydrogel from a hydrolyzed highly cross-linked AAm gel resulted in tough hydrogels. Those gels exhibited finite tensile behavior similar to that of conventional DN hydrogels. Moreover, craze-like patterns were observed during tensile loading of a DN hydrogel synthesized from a hydrolyzed highly cross-linked first network and a loosely cross-linked second network. The patterns remained in the gel even after strain hardening at high stretch ratios. The craze-like pattern formation was suppressed by increasing the concentration of cross-linking monomer in the second polymerization step. Crack propagation in DN hydrogels synthesized using hydrolysis was also studied by applying a tensile load on notched specimens.

Surgical treatment of achalasia: transabdominal versus transthoracic cardiomyotomy.

BACKGROUND: Achalasia is a primary esophageal motor disorder involving the body of the esophagus and lower esophageal sphincter. The mechanism is destruction of the myenteric plexus after a viral infection. Multiple methods of treatment with variable results induced in achalasia. MATERIALS AND METHODS: We analyzed 70 patients with achalasia that underwent surgical treatment with transabdominal or transthoracic cardiomyotomy from 1982 to 2008 in Mashhad (Ghaem and Omid) hospital and at least 2 years follow up for evaluated result of surgery. RESULTS: The mean age was 39.2 ± 9.42 years and the M/F = 0.89. The most common symptom was dysphagia (100%). The interval between beginnings of symptoms to a definitive diagnosis was 10.6 ± 8.3 month. The ratio between the two techniques was 35/35 = 1. In 67.1% of patients, a previous history of pneumatic dilation was reported. Long-term good results after surgery were seen in 77.2% of patients. Recurrence after surgical treatment was seen in 22.8%. A comparison of the two techniques (with or without antireflux surgery), showed a greater failure rate in transabdominal cardiomyotomy without the antireflux protocol (8/15 = 40%), but by the chi- square test, the difference was not statistically significant (P = 0.107). The most common complication after surgery was esophageal leakage (2.85%), and mortality was zero. In recurrence, most patients underwent pneumatic dilation (9/16 = 56.2%), and if surgery was needed, all patients underwent a transthoracic approach with antireflux treatment. CONCLUSION: Based on the good, long-term results with the surgical treatment of achalasia, surgery is recommended in most patients. A transthoracic or transabdominal approach had good, long-term results, but a transthoracic approach had better results and usually did not need antireflux surgery.

Tracheobronchopulmonary carcinoid tumors: analysis of 40 patients.

INTRODUCTION: Carcinoid tumors are a type of neuroendocrine tumors which usually involve the upper airways and the patients most often complain of cough and hemoptysis. MATERIALS AND METHODS: This study was performed from 1990 through 2007 on 40 patients with carcinoid tumor who had been followed up for at least 3 years. The statistical analysis were based on tumor epidemiology, treatment and the 3-year survival. The factors influencing the survival were analyzed using SPSS and exact Fisher test. RESULTS: M/F was 16/24 with mean age 34 years. Their most common symptoms were coughing (90%) . The left main bronchus was the most common site of involvement (25%). 95% of all the cases underwent surgery and 5% of the patients underwent chemoradiotherapy due to distant metastasis . The most common surgical procedure was lobectomy or biloectomy (57.8%). Bronchial sleeve resection was performed on 10.4% of the patients. The most common pathology was the typical form (90%) and 5% of the madiastinal lymph nodes were involvd all of the atypical type. Carcinoid syndrome was seen in one patient (2.5%) and post operative adjuvant treatment was done in 5% of the patients after surgery because of mediastinal lymph node involvement. Post operative recurrence occurred in one patient (2.6%) of the atypical form with mediastinal lymph nodes involvement. The most common complication of surgery was a long- term air leakage (10.4%) and the surgical death rate was 0%. 3-year survival was 92.5%. The factors influencing the survival included the pathological type, distant metastasis and mediastinal lymph node involvement. CONCLUSION: Carcinoid tumors have mostly been responsive to surgical intervention, resulting in a long term survival.

Surgical management of bronchiectasis: analysis of 277 patients.

BACKGROUND: Bronchiectasis is a permanent irreversible dilatation of the bronchial wall, often arising from inadequate treatment of a pulmonary infection. In recent years, the incidence of bronchiectasis has decreased mainly due to improved medical treatment of respiratory infections. However, the disease still constitutes a health problem in developing countries. METHOD: We reviewed 277 patients with bronchiectasis who underwent pulmonary resection in the Ghaem & Omid hospitals affiliated to Mashhad University of Medical Sciences in Iran from 1985 to 2008. The patients were evaluated for age, sex, clinical features, etiology, type of surgical procedure, morbidity, mortality and treatment outcomes. RESULTS: A total of 277 patients were enrolled in this study [200 males (72.2%) and 77 females (27.7%)]. Mean patient age was 34.7 years. The most common symptom was productive cough (79.4%). The most common etiology was pulmonary infection (77.6%). The disease was bilateral in 62 cases (22.3%) and the most common site of involvement was the left lower lobe (55%). The most common surgical technique for the unilateral form was lobectomy (42.2%) and one-sided lobectomy with segmentectomy of the other side in 25 patients with bilateral bronchiectasis. Mortality and morbidity rates were 0.7% and 15.8%, respectively. The most common complication was wound infection (5.7%). The mean follow-up was 4.5 years. 68.5% of patients were symptom-free at the last postoperative evaluation, 23.8% had an improvement in their symptoms, and 7.5% of patients showed no improvement. Statistically, complete resection had a better outcome. CONCLUSION: In conclusion, surgery is an acceptable treatment in bronchiectasis and has low mortality and morbidity rates. The best outcomes were observed after complete resection. In selected bilateral cases, resection was used with acceptable outcomes.