Enhanced Glucose-induced Intracellular Signaling Promotes Insulin Hypersecretion: Pancreatic Beta-cell Functional Adaptations In A Model Of Genetic Obesity And Prediabetes.

Obesity is associated with insulin resistance and is known to be a risk factor for type-2 diabetes. In obese individuals, pancreatic beta-cells try to compensate for the increased insulin demand in order to maintain euglycemia. Most studies have reported that this adaptation is due to morphological changes. However, the involvement of beta-cell functional adaptations in this process needs to be clarified. For this purpose, we evaluated different key steps in the glucose-stimulated insulin secretion (GSIS) in intact islets from female ob/ob obese mice and lean controls. Obese mice showed increased body weight, insulin resistance, hyperinsulinemia, glucose intolerance and fed hyperglycemia. Islets from ob/ob mice exhibited increased glucose-induced mitochondrial activity, reflected by enhanced NAD(P)H production and mitochondrial membrane potential hyperpolarization. Perforated patch-clamp examination of beta-cells within intact islets revealed several alterations in the electrical activity such as increased firing frequency and higher sensitivity to low glucose concentrations. A higher intracellular Ca(2+) mobilization in response to glucose was also found in ob/ob islets. Additionally, they displayed a change in the oscillatory pattern and Ca(2+) signals at low glucose levels. Capacitance experiments in intact islets revealed increased exocytosis in individual ob/ob beta-cells. All these up-regulated processes led to increased GSIS. In contrast, we found a lack of beta-cell Ca(2+) signal coupling, which could be a manifestation of early defects that lead to beta-cell malfunction in the progression to diabetes. These findings indicate that beta-cell functional adaptations are an important process in the compensatory response to obesity.

Epicardial And Pericardial Fat In Type 2 Diabetes: Favourable Effects Of Biliopancreatic Diversion.

Ectopic fat is often identified in obese subjects who are susceptible to the development of type 2 diabetes mellitus (T2DM). The ectopic fat favours the decrease in insulin sensitivity (IS) and adiponectin levels. We aimed to evaluate the effect of biliopancreatic diversion (BPD) on the accumulation of ectopic fat, adiponectin levels and IS in obese with T2DM. A nonrandomised controlled study was performed on sixty-eight women: 19 lean-control (23.0 ± 2.2 kg/m(2)) and 18 obese-control (35.0 ± 4.8 kg/m(2)) with normal glucose tolerance and 31 obese with T2DM (36.3 ± 3.7 kg/m(2)). Of the 31 diabetic women, 20 underwent BPD and were reassessed 1 month and 12 months after surgery. The subcutaneous adipose tissue, visceral adipose tissue, epicardial adipose tissue and pericardial adipose tissue were evaluated by ultrasonography. The IS was assessed by a hyperglycaemic clamp, applying the minimal model of glucose. One month after surgery, there was a reduction in visceral and subcutaneous adipose tissues, whereas epicardial and pericardial adipose tissues exhibited significant reduction at the 12-month assessment (p < 0.01). Adiponectin levels and IS were normalised 1 month after surgery, resembling lean-control values and elevated above the obese-control values (p < 0.01). After 12 months, the improvement in IS and adiponectin was maintained, and 17 of the 20 operated patients exhibited fasting glucose and glycated haemoglobin within the normal range. After BPD, positive physiological adaptations occurred in grade I and II obese patients with T2DM. These adaptations relate to the restoration of IS and decreased adiposopathy and explain the acute (1 month) and chronic (12 months) improvements in the glycaemic control.

Biópsia hepática por laparotomia paracostal em bovinos e búfalos

A técnica de biópsia hepática em ruminantes tem importante valor no diagnóstico clínico de doenças tóxicas e metabólicas, em especial nos desequilíbrios minerais. As técnicas mais comumente utilizadas restringem análises devido ao limitado volume de tecido obtido. No presente trabalho, avaliou-se o uso de uma técnica de biópsia hepática por laparotomia paracostal em bovinos e búfalos. Foram utilizados 10 bovinos e 10 búfalos hígidos. Os animais foram mantidos em estação, sedados com xilazina e infiltrados localmente com lidocaína e epinefrina. O acesso à cavidade abdominal foi realizado por meio de uma incisão dorso-ventral de 15cm no flanco direito, iniciada ventralmente (cerca de 4-5cm) ao processo transverso da 2a ou 3a vértebra lombar e situada caudalmente (cerca de 4cm) e paralelamente à 13a costela, obtendo-se visualização do fígado. Foi então realizado pinçamento do bordo caudal do órgão com pinça Doyen para remoção de fragmento hepático (2 a 4g). Procedeu-se o fechamento da cavidade abdominal como de rotina. Foram analisados os parâmetros bioquímicos e hematológicos antes do procedimento (tempo zero) e após 24 horas, 48 horas, 5 dias e 10 dias após a biópsia. Todas as variáveis bioquímicas estudadas retornaram aos valores basais 5 e 10 dias após o procedimento nos bovinos e búfalos, respectivamente. O tempo médio de cirurgia por animal foi de 25 minutos. A biópsia hepática por laparotomia paracostal demonstrou ser uma técnica eficaz e de baixo risco à saúde dos animais, permitindo a coleta de suficiente quantidade de tecido hepática para realização de múltiplas análises.

Sliding wear of weld layers with application to cane mill shaft rebuilding

Three welding procedures used to rebuild worn shafts in sugar cane mills were analysed: two submerged arc welding processes and one flux cored arc welding (FCAW) process. Sliding wear tests were in accordance with ASTM G 77 standard, using rings of welding material, blocks of bronze SAE 67, and oil as lubricant. The worn surfaces of rings and blocks were analysed by scanning electron microscopy to determine the wear mechanisms. High contact pressure, high operating temperature, and low relative speed were applied in sliding wear tests to match the conditions in sugar cane mills. Transferred material and evidence of adhesive junctions were detected. Additionally, hardened fragments produced abrasive grooves on the worn surfaces. The welding deposits that presented strong adhesion on the worn surface showed higher mass loss than the materials that presented more abrasive characteristics. Plastic mechanical properties were measured and related to the mass loss. The tested materials presented similar hardness but different yield stress and hardening coefficient. A relationship between wear, strain hardening coefficient, and yield stress was found. The welding deposit that presented the highest hardening coefficient showed the highest mass loss, with evidence of severe adhesion on the worn surface.

Intrahepatic Glissonian Approach for Pure Laparoscopic Left Hemihepatectomy

Background: Recent advances in laparoscopic devices and experience with advanced techniques have increased the indications for laparoscopic liver. Aim: The aim of this work was to present a video with technical aspects of a pure laparoscopic left hemi-hepatectomy (segments 2, 3, and 4) by using the intrahepatic Glissonian approach and control of venous outflow without hilar dissection or the Pringle maneuver. Patient and Method: A 63-year-old woman with a 5-cm solitary liver metastasis was referred for treatment. Four trocars were used. The left lobe was pulled upward and the lesser omentum was divided, exposing Arantius' ligament. This ligament is a useful landmark for the identification of the main left Glissonian pedicle. A small anterior incision was made in front of the hilum, and a large clamp was introduced behind the Arantius' ligament toward the anterior incision, allowing control of the left main sheath. Ischemic discoloration of the left liver was achieved and marked with cautery. The vascular clamp was replaced by a stapler. If ischemic delineation was coincident with a previously marked area, the stapler was fired. The left hepatic vein was dissected and encircled. Parenchymal transection and vascular control of the hepatic veins were accomplished with a Harmonic scalpel and an endoscopic stapling device, as appropriate. All these steps were performed without the Pringle maneuver and without hand assistance. Results: Operative time was 220 minutes with minimum blood loss. Hospital stay was 4 days. Pathology showed free surgical margins. The patient is alive with no signs of recurrence 18 months after the operation. Conclusion: Totally laparoscopic left hemihepatectomy is safe and feasible in selected patients and should be considered for patients with benign or malignant liver neoplasms. The described technique, with the use of the intrahepatic Glissonian approach and control of venous outflow, may facilitate laparoscopic left hemihepatectomy by reducing the technical difficulties in pedicle control and may decrease bleeding during liver transection.

Microstructure and mechanical properties of laser-welded joints of TWIP and TRIP steels

With the aim of investigating a laser-welded dissimilar joint of TWIP and TRIP steel sheets, the microstructure was characterized by means of OM, SEM, and EBSD to differentiate the fusion zone, heat-affected zone, and the base material. OIM was used to differentiate between ferritic, bainitic, and martensitic structures. Compositions were measured by means of optical emission spectrometry and EDX to evaluate the effect of manganese segregation. Microhardness measurements and tensile tests were performed to evaluate the mechanical properties of the joint. Residual stresses and XRD phase quantification were used to characterize the weld. Grain coarsening and martensitic areas were found in the fusion zone, and they had significant effects on the mechanical properties of the weld. The heat-affected zone of the TRIP steel and the corresponding base material showed considerable differences in the microstructure and properties. (C) 2009 Elsevier B.V. All rights reserved.

Sigma phase morphologies in cast and aged super duplex stainless steel

Solution annealed and water quenched duplex and super duplex stainless steels are thermodynamically metastable systems at room temperature. These systems do not migrate spontaneously to a thermodynamically stable condition because an energy barrier separates the metastable and stable states. However, any heat input they receive, for example through isothermal treatment or through prolonged exposure to a voltaic arc in the welding process, cause them to reach a condition of stable equilibrium which, for super duplex stainless steels, means precipitation of intermetallic and carbide phases. These phases include the sigma phase, which is easily identified from its morphology, and its influence on the material`s impact strength. The purpose of this work was to ascertain how 2-hour isothermal heat treatments at 920 degrees C and 980 degrees C affect the microstructure of ASTM A890/A890M GR 6A super duplex stainless steel. The sigma phase morphologies were found to be influenced by these two aging temperatures, with the material showing a predominantly lacy microstructure when heat treated at 920 degrees C and block-shaped when heat treated at 980 degrees C. (C) 2009 Elsevier Inc. All rights reserved.

Fatigue behaviour of friction stir welded AA2024-T3 alloy: longitudinal and transverse crack growth

The fatigue crack growth properties of friction stir welded joints of 2024-T3 aluminium alloy have been studied under constant load amplitude (increasing-Delta K), with special emphasis on the residual stress (inverse weight function) effects on longitudinal and transverse crack growth rate predictions (Glinka`s method). In general, welded joints were more resistant to longitudinally growing fatigue cracks than the parent material at threshold Delta K values, when beneficial thermal residual stresses decelerated crack growth rate, while the opposite behaviour was observed next to K-C instability, basically due to monotonic fracture modes intercepting fatigue crack growth in weld microstructures. As a result, fatigue crack growth rate (FCGR) predictions were conservative at lower propagation rates and non-conservative for faster cracks. Regarding transverse cracks, intense compressive residual stresses rendered welded plates more fatigue resistant than neat parent plate. However, once the crack tip entered the more brittle weld region substantial acceleration of FCGR occurred due to operative monotonic tensile modes of fracture, leading to non-conservative crack growth rate predictions next to K-C instability. At threshold Delta K values non-conservative predictions values resulted from residual stress relaxation. Improvements on predicted FCGR values were strongly dependent on how the progressive plastic relaxation of the residual stress field was considered.

Ultrasound, eddy current and magnetic Barkhausen noise as tools for sigma phase detection on a UNS S31803 duplex stainless steel

Sigma phase is a deleterious one which can be formed in duplex stainless steels during heat treatment or welding. Aiming to accompany this transformation, ferrite and sigma percentage and hardness were measured on samples of a UNS S31803 duplex stainless steel submitted to heat treatment. These results were compared to measurements obtained from ultrasound and eddy current techniques, i.e., velocity and impedance, respectively. Additionally, backscattered signals produced by wave propagation were acquired during ultrasonic inspection as well as magnetic Barkhausen noise during magnetic inspection. Both signal types were processed via a combination of detrended-fluctuation analysis (DFA) and principal component analysis (PCA). The techniques used were proven to be sensitive to changes in samples related to sigma phase formation due to heat treatment. Furthermore, there is an advantage using these methods since they are nondestructive. (C) 2010 Elsevier B.V. All rights reserved.

MODELLING AND CONTROL OF ERSW PROCESSES BY NEURONAL NETWORK

A study on the use of artificial intelligence (AI) techniques for the modelling and subsequent control of an electric resistance spot welding process (ERSW) is presented. The ERSW process is characterized by the coupling of thermal, electrical, mechanical, and metallurgical phenomena. For this reason, early attempts to model it using computational methods established as the methods of finite differences, finite element, and finite volumes, ask for simplifications that lead the model obtained far from reality or very costly in terms of computational costs, to be used in a real-time control system. In this sense, the authors have developed an ERSW controller that uses fuzzy logic to adjust the energy transferred to the weld nugget. The proposed control strategies differ in the speed with which it reaches convergence. Moreover, their application for a quality control of spot weld through artificial neural networks (ANN) is discussed.

Comparison between DC(+) and Square Wave AC SAW Current Outputs to Weld AISI 304 for Low-Temperature Applications

Welded equipment for cryogenic applications is utilized in chemical, petrochemical, and metallurgical industries. One material suitable for cryogenic application is austenitic stainless steel, which usually doesn`t present ductile/brittle transition temperature, except in the weld metal, where the presence of ferrite and micro inclusions can promote a brittle failure, either by ferrite cleavage or dimple nucleation and growth, respectively. A 25-mm- (1-in.-) thick AISI 304 stainless steel base metal was welded with the SAW process using a 308L solid wire and two kinds of fluxes and constant voltage power sources with two types of electrical outputs: direct current electrode positive and balanced square wave alternating current. The welded joints were analyzed by chemical composition, microstructure characterization, room temperature mechanical properties, and CVN impact test at -100 degrees C (-73 degrees F). Results showed that an increase of chromium and nickel content was observed in all weld beads compared to base metal. The chromium and nickel equivalents ratio for the weld beads were always higher for welding with square wave AC for the two types of fluxes than for direct current. The modification in the Cr(eq)/Ni(eq) ratio changes the delta ferrite morphology and, consequently, modifies the weld bead toughness at lower temperatures. The oxygen content can also affect the toughness in the weld bead. The highest absorbed energy in a CVN impact test was obtained for the welding condition with square wave AC electrical output and neutral flux, followed by DC(+) electrical output and neutral flux, and square wave AC electrical output and alloyed flux.

ASTM A923-Practice A application to identify intermetallic phases in a UNS S32750 superduplex welded joint

Duplex and superduplex stainless steels present superior mechanical and corrosion properties when compared to usual stainless steels. This superiority is based on chemical composition when in a balanced microstructure (approximately 50% of ferrite). During welding, changes may occur in both, the chemical composition and volume fraction of phases in the material, which may generate the presence of intermetallic phases and, as a consequence, modify the mechanical and corrosion properties of this group of stainless steels. The objective of this work is to apply ASTM A923- Practice A to verify the presence of intermetallic phases in welded joints of UNS 32750 su-perduplex stainless steel. Tubes of UNS 32750, with external diameters of 18 and 44 mm and a thickness of 1.5 mm, were welded using orbital GTAW, with filler metal 25Cr-10Ni-4Mo and a diameter of 0.8 mm. The metal-based and welded joints were characterized by optical and scanning electron microscopy. The results showed that there was no precipitation of the intermetallic phase, such as sigma phase, detected by ASTM A923, but the HAZ of the two tubes studied presented small regions with chromium nitrides, which can also change the properties of welded joins.

Fretting fatigue in overhead conductors: Rig design and failure analysis of a Grosbeak aluminium cable steel reinforced conductor

The performance optimisation of overhead conductors depends on the systematic investigation of the fretting fatigue mechanisms in the conductor/clamping system. As a consequence, a fretting fatigue rig was designed and a limited range of fatigue tests was carried out at the middle high cycle fatigue regime in order to access an exploratory S-N curve for a Grosbeak conductor, which was mounted on a mono-articulated aluminium clamping system. Subsequent to these preliminary fatigue tests, the components of the conductor/clamping system, such as ACSR conductor, upper and lower clamps, bolt and nuts, were subjected to a failure analysis procedure in order to investigate the metallurgical free variables interfering on the fatigue test results, aiming at the optimisation of the testing reproducibility. The results indicated that the rupture of the planar fracture surfaces observed in the external At strands of the conductor tested under lower bending amplitude (0.9 mm) occurred by fatigue cracking (I mm deep), followed by shear overload. The V-type fracture surfaces observed in some At strands of the conductor tested under higher bending amplitude (1.3 mm) were also produced by fatigue cracking (approximately 400 mu m deep), followed by shear overload. Shear overload fracture (45 degrees fracture surface) was also observed on the remaining At wires of the conductor tested under higher bending amplitude (1.3 mm). Additionally, the upper and lower Al-cast clamps presented microstructure-sensitive cracking, which was folowed by particle detachment and formation of abrasive debris on the clamp/conductor tribo-interface, promoting even further the fretting mechanism. The detrimental formation of abrasive debris might be inhibited by the selection of a more suitable class of as-cast At alloy for the production of clamps. Finally, the bolt/nut system showed intense degradation of the carbon steel nut (fabricated in ferritic-pearlitic carbon steel, featuring machined threads with 190 HV), with intense plastic deformation and loss of material. Proper selection of both the bolt and nut materials and the finishing processing might prevent the loss in the clamping pressure during the fretting testing. It is important to control the specification of these components (clamps, bolt and nuts) prior to the start of large scale fretting fatigue testing of the overhead conductors in order to increase the reproducibility of this assessment. (c) 2008 Elsevier Ltd. All rights reserved.

Cracking of 2.25Cr-1.0Mo steel tube/stationary tube-sheet weldment of a heat-exchanger

The premature failure of a horizontal heat-exchanger, which occurred after service exposure at 580 degrees C for 50,000 h, revealed the occurrence of extensive through-thickness cracking in approximately 40% of the tube/stationary tube-sheet welds. Additionally, the internal surface of the welded joint featured intensive secondary intergranular cracking (up to 250 mu m deep), preferential formation of a 150 mu m thick layer of (Fe, Cr)(3)O-4 and internal intergranular oxidation (40 mu m deep). The welded region also showed intense carbon pick-up and, as consequence, severe precipitation of intergranular M7C3 and M23C6 carbides. The fracture surface was composed of two distinct regions: a ""planar"" region of 250 mu m, formed due to the stable crack growth along by the intergranular oxidation; and a slant region with radial marks, formed by the fast crack growth along the network of intergranular carbides. The association of intergranular oxidation pre-cracks with microstructural embrittlement promoted the premature failure, which took place by an overload mechanism, probably due to the jamming of the floating tube-sheet during the maintenance halt (cooling operation). (C) 2007 Elsevier Ltd. All rights reserved.

Purification and characterization of Ts15, the first member of a new alpha-KTX subfamily from the venom of the Brazilian scorpion Tityus serrulatus

Voltage-gated potassium channel toxins (KTxs) are basic short chain peptides comprising 23-43 amino acid residues that can be cross-linked by 3 or 4 disulfide bridges. KTxs are classified into four large families: alpha-, beta-, gamma- and kappa-KTx. These peptides display varying selectivity and affinity for K(v) channel subtypes. In this work, a novel toxin from the Tityus serrulatus venom was isolated, characterized and submitted to a wide electrophysiological screening on 5 different subtypes of Nay channels (Na(V)1.4; Na(V)1.5; Na(V)1.6; Na(V)1.8 and DmNa(V)1) and 12 different subtypes of Kv channels (K(V)1.1 - K(V)1.6; K(V)2.1; K(V)3.1; K(V)4.2; K(V)4.3; Shaker IR and ERG). This novel peptide, named Ts15, has 36 amino acids, is crosslinked by 3 disulfide bridges, has a molecular mass of 3956 Da and pI around 9. Electrophysiological experiments using patch clamp and the two-electrode voltage clamp techniques show that Ts15 preferentially blocks K(V)1.2 and K(V)1.3 channels with an IC(50) value of 196 +/- 25 and 508 +/- 67 nM, respectively. No effect on Na(V) channels was observed, at all tested concentrations. Since Ts15 shows low amino acid identity with other known KTxs, it was considered a bona fide novel type of scorpion toxin. Ts15 is the unique member of the new alpha-Ktx21 subfamily and therefore was classified as alpha-Ktx21.1. (C) 2011 Elsevier Ltd. All rights reserved.