Charge carriers and small-polaron migration as the origin of intrinsic dielectric anomalies in multiferroic TbMnO3 polycrystals

Temperature-dependent and frequency-dependent dielectric investigations have been performed in TbMnO3 polycrystals sintered in either oxidative or reductive atmospheres. The results revealed the occurrence of two dielectric anomalies above 100 K, which are caused by the thermal activation of charge carriers and their motion in grain cores and grain boundaries. The temperature dependence of the bulk dc conductivity was also analysed and indicates that charge carriers move between inequivalent sites according to a variable-range-hopping mechanism. Also, a strong correlation between dielectric properties and crystalline structure was observed. Furthermore, a low-temperature dielectric relaxation, commonly reported in rare-earth manganite crystals, was observed in both samples. This relaxation follows the empirical Cole-Cole model and was attributed to small-polaron tunnelling. Polaron motion was observed to be affected by the magnetic transitions, structural properties and intrinsic anisotropies in TbMnO3. It is also worth mentioning that the dielectric anomaly due to motion of charge carriers in grain boundaries is the only one of extrinsic origin, while the anomalies related to carrier motion in grain cores and small-polaron tunnelling are intrinsic to TbMnO3.

Study on the observation of Eu2+ and Eu3+ valence states in low silica calcium aluminosilicate glasses

The optical, magnetic and structural properties of Eu doped low silica calcium aluminosilicate glasses were investigated. The optical absorption coefficient presented two bands at 39,246 and 29,416 cm(-1), which were assigned respectively to the [Formula in text], and [Formula in text] transitions of Eu(2+). The fluorescence measured at 300 K on a sample doped with 0.5 wt% of Eu(2)O(3) exhibited a broad band centered at 17,350 cm(-1), which is attributed to the [Formula in text] transition of Eu(2+), whereas the additional peaks are due to the [Formula in text] transitions of Eu(3+). From magnetization and XANES data it was possible to evaluate the fractions of Eu(2+) and Eu(3+) for the sample doped with 0.5 and 5.0 wt% of Eu(2)O(3), the values of which were approximately 30 and 70%, respectively.

The role of liver transplantation in patients with Caroli's disease

Caroli's disease, characterized by segmental or diffuse dilation of the intrahepatic biliary ducts, is a rare disease which is difficult to treat. The course of the disorder is characterized by recurrent episodes of cholangitis and hospital stays, with a consequent loss of quality-of-life and productive capacity, often ending in death due to uncontrolled infection. Endoscopic drainage of the bile duct, percutaneously or surgically, is palliative, and presents bad results in the follow-up of these patients. Orthotopic liver transplantation appears to be an effective curative option for the treatment of patients with Caroli's disease associated to complications. The authors present the course of two cases of this disease, associated with congenital fibrosis of the liver worsened by repeated episodes of cholangitis, submitted to orthotopic liver transplantation.

A comparison between topical and infiltrative bupivacaine and intravenous meperidine for postoperative analgesia after inguinal herniorrhaphy

The purpose of the present study is to compare postoperative analgesia offered by the simple instillation of local anesthetic on the surgical wound, its infiltration with the same local anesthetic, and the use of an intravenous opioid. Sixty patients were divided into the three analgesia groups to be studied: instillation of local anesthetic (Group I), injection of local anesthetic (Group II), and intravenous opioid (Group III). The pain was quantified using the visual analogue scale. It was observed that there was better analgesia in Groups I and II during the first 6 hours postoperatively as compared with Group III (P < 0.0001). At the end of the 12 hours the three modes of analgesia proved comparable. However, after 24 hours there was better analgesic development in Group I, whereas Group II had greater postoperative morbidity. We conclude that the instillation of local anesthesia provides analgesia during the immediate postoperative period comparable to local infiltration using the same anesthetic. Both regional analgesia methods are more effective analgesics during the first 6 hours than are intravenous opioids. Furthermore the simple instillation of local anesthetic allows better analgesic evolution of the surgical wound after the first 24 hours considering the lower rate of resulting complications.

Comparative post-operative study of prostheses, with and without an anti-reflux valve system, in the palliative treatment of esophageal carcinoma

BACKGROUND/AIMS

Palliative treatment of advanced esophageal carcinoma by esophageal tunnelization with a prosthesis allows immediate relief of dysphagia. However, the procedure is subject to a high rate of morbidity, including gastroesophageal reflux (GER) present in all patients with a prosthesis positioned through the gastroesophageal junction, resulting in complications (pyrosis, aspiration pneumonias, sleep disorders) and reduced quality of life in these patients who already have a lower rate of survival. In an attempt to reduce GER and its complications, the authors created a surgical prosthesis coupled to an anti-reflux valve system, comparing it to the use of an esophageal prosthesis without an anti-reflux valve mechanism.

METHODOLOGY

Twenty-two patients were allocated to 2 tunnelization groups: esophageal prosthesis without an anti-reflux valve mechanism (group 1) and surgical prosthesis coupled to an anti-reflux valve system (group 2). The GER was quantified measuring esophageal-gastric pH, and using fluoroscopy, contrast radiographs and esophageal emptying scintigraphy. Initially, the pH of secretions in S1 (esophagus) and S2 (stomach) was determined using reagent strips after aspirating their contents with different syringes. First with the patient seated at rest in bed, later performing a Valsalva maneuver, deep breathing and forced coughing. The same procedure was performed with the patient in left lateral decubitus, right lateral decubitus, and dorsal decubitus with the head of the bed lowered to 20 degrees. After finishing these maneuvers, 15 ml of 1 molar acetic acid were infused through the catheter positioned in the antrum, and, after 5 min, S1 and S2 material sampling was repeated in the same positions as mentioned above.

RESULTS

The pH values between the various positions and maneuvers performed in each group separately were not significantly different, but, if we compare the 2 groups, and the secretions obtained in S1 and S2, there was a significant difference in pH measures in all positions. In the patients in group 1, S1 presented a mean pH ranging from 2.87-3.62 in the initial measures, and between 2.17 and 3.5 after the infusion of 15 ml of 1 molar acetic acid. On the other hand, in group 2, the mean pH of S1 remained between 6.34 and 8.32 in the initial measures and between 4.99 and 7.33 in the presence of acid infusion. At the level of S2, the pH remained unchanged between 2 and 2.7, in both groups.

CONCLUSIONS

The authors conclude that the association of an esophageal prosthesis with a valve system significantly reduces GER, as compared with its use alone. Furthermore, it allows marked reduction of the symptoms and resulting complications, and does not interfere clinically with esophageal emptying. It thus significantly improves the quality of life of these patients.

Pancreatic fistula after pancreaticoduodenectomy: a comparison between patients with periampullary tumors and chronic pancreatitis

BACKGROUND/AIMS

Whether the frequency of anastomotic leak after pancreaticoduodenectomy for benign diseases is greater than for malignant conditions and whether fistula development is associated with surgical mortality remains controversial. The purpose of this study is to compare the incidence of anastomotic leak in patients operated on for chronic pancreatitis and periampullary tumors.

METHODOLOGY

The authors retrospectively reviewed the charts of 67 patients (46 males, 21 females, mean age 47 years) submitted to pancreaticoduodenectomy for chronic pancreatitis and periampullary tumors between 1990 and 1996.

RESULTS

In 44 patients with periampullary cancers, pancreatic fistula developed in 13 (29%) cases, and in 6 (26%) of the 23 patients with chronic pancreatitis (p>0.05). Of the 19 patients who developed this complication, 5 (26.3%) died, and in the remaining 48 cases, there was only one (2.1%) death (p<0.05).

CONCLUSION

The frequency of pancreatic fistula after pancreaticoduodenectomy in patients with periampullary tumors and chronic pancreatitis is not different, but the presence of a fistula is strongly involved in postoperative mortality.