Modeling Ionic Polymer-Metal Composites with Space-Time Adaptive Multimesh hp-FEM

We are concerned with a model of ionic polymer-metal composite (IPMC) materials that consists of a coupled system of the Poisson and Nernst-Planck equations, discretized by means of the finite element method (FEM). We show that due to the transient character of the problem it is efficient to use adaptive algorithms that are capable of changing the mesh dynamically in time. We also show that due to large qualitative and quantitative differences between the two solution components, it is efficient to approximate them on different meshes using a novel adaptive multimesh hp-FEM. The study is accompanied with numerous computations and comparisons of the adaptive multimesh hp-FEM with several other adaptive FEM algorithms.     

Enhanced insulin sensitivity in extrarenal potassium handling in uremic rats.

Translocation of potassium to the intracellular compartment is impaired in advanced chronic renal failure. The purpose of this study was to evaluate the role of endogenous insulin in the disposal of an oral potassium load in uremia. Experiments were done on male Sprague-Dawley rats. Chronic renal failure (CRF) was induced by 3/4 nephrectomy. The results show that the addition of oral glucose to a potassium load was more effective in the translocation of potassium to the intracellular compartment in uremic animals. Further, suppression of endogenous insulin secretion with somatostatin caused a much higher increase in plasma potassium (K) of uremic rats (1.09 +/- 0.15 mEq/liter in CRF vs. 0.28 +/- 0.03 mEq/liter in control). Experiments to assess the activity of the Na pump were done in soleus muscles derived from these animals. Although a 50% reduction of the basal Na pump activity was found in the uremic muscles, the addition of insulin 100 mU/ml caused a relatively greater stimulation of ouabain-sensitive 86Rb uptake in the uremic muscle as compared to the control tissue (203% vs. 77% increment). These data suggest a greater sensitivity to insulin action on extrarenal potassium disposal in uremia.     

Original and modified technique of tie-over dressing: Method and application in burn patients

In burn patients, meshed split thickness skin grafts are commonly used on large and non-flat areas whom immobilization is difficult to achieve. The frequent mobilizations of burn patients can make the graft slip and prevent the revascularization and therefore the taking of the skin graft. In order to prevent this pitfall, we modified and adapted the tie-over dressing procedure. The giant running tie-over dressing enables large skin grafts to be applied to their wound bed and therefore helps revascularization. Some cautions are necessary in order to avoid any infection. This original and easy-to-perform procedure answers to the difficulties of large split-thickness skin grafts in burn patients.     

Use of Non-Echo-Planar Diffusion-Weighted MR Imaging for the Detection of Cholesteatomas in High-Risk Tympanic Retraction Pockets

BACKGROUND AND PURPOSE:Non-echo-planar DWI MR imaging (including the HASTE sequence) has been shown to be highly sensitive and specific for large cholesteatomas. The purpose of this study was to determine the diagnostic accuracy of HASTE DWI for the detection of incipient cholesteatoma in high-risk retraction pockets.MATERIALS AND METHODS:This was a prospective study of 16 patients who underwent MR imaging with HASTE DWI before surgery. Surgeons were not informed of the results, and intraoperative findings were compared against the radiologic diagnosis. Sensitivity, specificity, and positive and negative predictive values were calculated.RESULTS:Among the 16 retraction pockets, 10 cholesteatomas were diagnosed intraoperatively (62.5%). HASTE showed 90% sensitivity, 100% specificity, 100% positive predictive value, and 85.7% negative predictive value in this group of patients. We found only 1 false-negative finding in an infected cholesteatoma.CONCLUSIONS:We demonstrate a high correlation between HASTE and surgical findings, suggesting that this technique could be useful for the early detection of primary acquired cholesteatomas arising from retraction pockets and could help to avoid unnecessary surgery.

Middle ear cholesteatomas are benign but locally aggressive nonneoplastic lesions composed of a keratinizing stratified squamous epithelial matrix, an inflammatory perimatrix, and desquamated keratin content.¹ Pathophysiologically, cholesteatomas are divided into congenital (epithelium trapped within the middle ear during fetal development) and acquired. Acquired cholesteatomas are further divided into primary (arising from a tympanic membrane retraction) and secondary (epithelium reaching the middle ear through a tympanic perforation, fracture, or iatrogenic procedure).^2,3 Cholesteatomas progressively erode the bony structures surrounding the middle ear (ossicles, facial nerve canal, bony labyrinth, and skull base), predisposing to a wide range of complications, including potentially severe infections such as meningitis and intracranial abscesses.⁴ Surgery is the only known curative treatment and should be performed early because less destruction allows more conservative and hearing-preserving procedures with a reduced risk of complications.Tympanic retraction pockets are invaginations of the tympanic membrane into the middle ear cleft caused by Eustachian tube dysfunction, which interferes with proper middle ear ventilation.⁵ The diagnosis of a “dangerous” or high-risk retraction pocket is proposed when the bottom of the pocket becomes hidden to the otomicroscope and/or starts retaining skin, because this may lead to primary acquired cholesteatoma.¹ Given that there is a continuum from tympanic retraction pockets to small cholesteatomas, the distinction between retraction pockets that have already developed a cholesteatoma and those that have not remains a problem in otologic surgery because conventional clinical and radiologic methods are often insufficient. In addition, dangerous retraction pockets and small cholesteatomas share similar clinical signs and symptoms, and it is often impossible to differentiate them via otomicroscopy. A substantial number of such patients undergo surgical procedures such as mastoidectomies or atticotomies, but only a subset actually have cholesteatomas.CT is the most widely used imaging technique for the detection of a middle ear mass and assessing tympanomastoid anatomy and the extent of bone erosion.⁶ However, it is nonspecific for cholesteatoma and relies on indirect signs for its diagnosis.^7,8 More recently, MR imaging techniques have been used to differentiate cholesteatoma from other middle ear masses, especially T1-weighted delayed postcontrast imaging and DWI.^9,10DWI techniques are based on the restriction of movement of water molecules, such as that caused by keratin-filled cholesteatomas, producing a hyperintense signal.¹¹ Conventional EPI has been displaced by non-EPI techniques when the temporal bone is the focus, because these sequences have fewer artifacts and thinner sections, allowing the detection of cholesteatomas as small as 2 mm.¹² Several studies of non-echo-planar (EP) DWI have provided excellent sensitivity and specificity for the detection of cholesteatomas. Currently, MR imaging is suggested when the diagnosis of cholesteatoma cannot be established by other means, often in the setting of congenital and residual/recurrent disease.¹⁰The purpose of this study was to evaluate the sensitivity and specificity of non-EP DWI for the detection of cholesteatomas in skin-retaining and/or otomicroscopically inaccessible tympanic retraction pockets.     

Effect of a simultaneous potassium and carbohydrate load on extrarenal K homeostasis in end-stage renal failure

Patients with chronic renal failure (CRF) are continuously exposed to hyperkalemia. In these patients the extrarenal disposal of a potassium load may be very important to determine the plasma potassium levels. We studied the effect of a combined oral load of potassium (0.5 mEq/kg body weight) and carbohydrate (0.5 g/kg body weight) to mimic normal ingestion of potassium. Eight CRF patients and 5 control subjects were studied. The maximal increase in plasma potassium levels achieved was significantly higher in the patients (1.07 +/- 0.1 mEq/l) than in controls (0.39 +/- 0.05 mEq/l). Basal insulin levels were higher in the CRF patients and increased with the oral potassium and carbohydrate load in both controls and patients. In the CRF patients only 58.9 +/- 3% of the potassium load was translocated to the intracellular space compared to 81 +/- 6% in the controls. No correlation was found between the acid base status and maximal potassium increase. We conclude that patients with CRF exhibit an impaired extrarenal handling of potassium and that this abnormality does not appear to be related to insulin secretion or acid base status.     

Nanoporous Carbide-Derived Carbon Material-Based Linear Actuators

Devices using electroactive polymer-supported carbon material can be exploited as alternatives to conventional electromechanical actuators in applications where electromechanical actuators have some serious deficiencies. One of the numerous examples is precise microactuators. In this paper, we show for first time the dilatometric effect in nanocomposite material actuators containing carbide-derived carbon (CDC) and polytetrafluoroetylene polymer (PTFE). Transducers based on high surface area carbide-derived carbon electrode materials are suitable for short range displacement applications, because of the proportional actuation response to the charge inserted, and high Coulombic efficiency due to the EDL capacitance. The material is capable of developing stresses in the range of tens of N cm^-2. The area of an actuator can be dozens of cm², which means that forces above 100 N are achievable. The actuation mechanism is based on the interactions between the high-surface carbon and the ions of the electrolyte. Electrochemical evaluations of the four different actuators with linear (longitudinal) action response are described. The actuator electrodes were made from two types of nanoporous TiC-derived carbons with surface area (S_A) of 1150 m² g^-1 and 1470 m² g^-1, respectively. Two kinds of electrolytes were used in actuators: 1.0 M tetraethylammonium tetrafluoroborate (TEABF₄) solution in propylene carbonate and pure ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMITf). It was found that CDC based actuators exhibit a linear movement of about 1% in the voltage range of 0.8 V to 3.0 V at DC. The actuators with EMITf electrolyte had about 70% larger movement compared to the specimen with TEABF₄ electrolyte.     

Mammaplasty for Mild and/or Ptotic Breast Through Short Incision at the Inframammary Sulcus: A Personal Approach

Small to moderate pexy and breast reduction have been treated through a 5-cm length access view incision placed at the inframammary sulcus. Resection of up to 450 g in each breast are obtained. Overlapping and plication of two glandular flaps dissected from the lower breast quadrants complete the suspension and fixation of the breast in its ideal position. The areola remain untouched.     

Sexual dimorphism of canine teeth of small dogs.

Sex-associated morphological characteristics were shown in the permanent canine teeth of dogs. Crowns and roots were respectively about 23 per cent and 40 per cent longer, and about 26 per cent and 50 per cent wider in males. The smaller crown: root ratio in males together with the greater root width indicate a dimorphism in the tooth anchorage mechanism. Ratios of widths of various regions of the teeth showed that the canine teeth of male dogs were not only larger but, because of their expanded midroot width, were of different contour to those of females. The differences in tooth size and contour far exceeded the general statural difference of about 6 per cent expected between the sexes. Evidence from other sources suggests that these differences may be due to a direct effect of circulating sex hormones on tooth development.     

Effect of chronic renal failure on Na,K-ATPase alpha 1 and alpha 2 mRNA transcription in rat skeletal muscle.

Previous studies have suggested that an alteration in the expression of the Na,K-ATPase of muscle may be an important determinant of enhanced insulin sensitivity in chronic renal failure. Therefore, in the present studies we have examined the effect of uremia on the Na,K-ATPase alpha isoforms in skeletal muscle, at the level of mRNA expression and enzymatic activity. The activity of the sodium pump, as measured ouabain-sensitive 86Rb/K uptake in soleus muscle, revealed a reduction in the activity in uremia, related to the increment in plasma creatinine values. The decrement in 86Rb uptake by the rat soleus muscle of experimental animals was associated with changes on Na,K-ATPase gene product. Northern analysis of mRNA revealed isoform-specific regulation of Na,K-ATPase by uremia in skeletal muscle: a decrease of approximately 50% in alpha 1 subunit Na,K-ATPase mRNA, as compared to controls. The decrement in alpha 1 mRNA correlates with the decreased activity of the Na,K-ATPase in uremia, under basal conditions and with the almost complete inhibition of the Na,K-ATPase, of uremic tissue by a concentration of 10(-5) M ouabain. Although the activity of the alpha 2 isoform pump was not modified by uremia, the 3.4-kb message for this enzyme was increased 2.2-fold; this discrepancy is discussed. Altogether these findings demonstrate that the defective extrarenal potassium handling in uremia is at least dependent in the expression of alpha 1 subunit of the Na,K-ATPase.