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In this study, the local Nusselt number and the convective heat transfer coefficient of water and two water-based nanofluids are determined in the thermal entrance region in a laminar pipe flow. The pressure drop and the friction factor are also measured. Three mass concentrations, up to 5%, of Al 2 O 3 -water and TiO 2 -water nanofluids were prepared from commercial stock solutions. The results show that the non-dimensional relationships that relate the friction factor to the Reynolds number and the local Nusselt number to the Graetz number are still valid for these nanofluids. Both the local heat transfer coefficient and the pressure drop increase with mass concentration at a constant Reynolds number due to the enhancement of the thermal conductivity and the rise of the viscosity. However, at a constant pumping power, we demonstrate that the addition of these particles degrades heat transfer during the whole process of thermal development. This can be explained by the fact that the boundary layer grows faster for nanofluids than for water at a constant pumping power. A conservative criterion has been developed to assess the thermal performance of nanofluids in the thermal entrance region of a pipe. It suggests that it may not be possible to increase the thermal performance of water in this region by adding common solid particles. [ABSTRACT FROM AUTHOR]

This work focuses on the nonlinear electrochemical (EC) activity of fluids and its impact on the accuracy of their thermophysical property measurements using the transient or periodically modulated hot wire method (THW or 3ωHW). This underestimated source of errors becomes crucial for nanofluids, where the thermal conductivity enhancement coefficient (k/k0 − 1) is small, requiring high-resolution measurements (below 1%). Theoretical predictions combining thermal and EC nonlinearities are confronted to experimental results obtained with two variants of 3ω cells. Water-based nanofluids (TiO2 and Al2O3) and water solutions of acetic acid, sodium hydroxide and sodium chloride were tested. The two classes of samples show different 3ω amplitude and phase behaviors, which is attributed to additional electrokinetic effects in nanofluids. For all studied samples an anti-correlation between the magnitude of the harmonics and the dc electrical resistivity of the samples was observed. A simple estimation method of 3ωHW errors is proposed consisting in measuring the 2nd harmonic in addition to the 3rd one. The combination of 2nd and 3rd harmonics allowed determining the nonlinearity coefficient which quantitatively characterizes the EC activity of samples. Eventually, the radical solution to avoid the discussed sources of errors is to use an electrically insulated hot wire sensor. [ABSTRACT FROM AUTHOR]

The effective thermophysical and optical properties of high density polyethylene (HDPE) filled with 50 μm and 5 μm particle sizes of expanded graphite (EG50, EG5) are characterized. The methods used were front- and back-detection modulated photothermal radiometry (FD-, BD-PTR) and BD-flash IR thermography. Results were interpreted according to one-dimensional heat diffusion models. The absolute thermal diffusivity was determined at low frequency from FD- and BD-PTR spectra, while the volumetric heat capacity, the thermal effusivity, and the optical absorption coefficient were determined from broad-band FD-PTR spectra. The directly obtained diffusivity values compare well with those calculated from the heat capacity and thermal effusivity, and with BD-flash results. The errors caused by the finite absorption coefficient of diluted samples are also evaluated and corrected for. A particle-size effect with the opposite influence on thermal and optical properties has been observed. Heat transport parameters of HDPE/EG composites are significantly enhanced (factor of 3 to 4 in thermal diffusivity) at low particle charge before reaching saturation above a 0.10 particle volume fraction. These features are explained in the framework of effective medium models by strongly non-spherical EG particles. [ABSTRACT FROM AUTHOR]

The purpose of this study was to compare the diagnostic interest of Hector Battifora mesothelial antigen-1 (HBME-1), thyroid peroxidase (TPO), and dipeptidyl aminopeptidase IV (DPP4) in thyroid fine-needle aspirates obtained from 200 resected thyroid lesions (55 colloid nodules, 54 follicular adenomas, 59 papillary cancers, and 32 follicular carcinomas). Hector Battifora mesothelial antigen-1 or TPO expression (% positive cells) and DPP4 staining score (12-point scale) were evaluated. Receiver operating characteristic (ROC) curves were plotted and optimal cutoff values for diagnosing malignancy were determined. The TPO ROC curve was consistently higher than the HBME-1 ROC curve. The TPO curve was also higher than the DPP4 curve with regard to sensitivity, but dipped below the DPP4 curve with regard to specificity. Using a cutoff value of <80% positive cells for TPO, >10% positive cells for HBME-1, and staining score > or =1 for DPP4, sensitivity to specificity ratios were 98-83% for TPO, 90-60% for HBME-1, and 88-80% for DPP4. Two particularly interesting findings of this study were the low negative likelihood ratio of TPO (0.02) allowing highly reliable exclusion of malignancy and the 100% specificity of DPP4 staining scores=12. Due to poor performance on follicular lesions, HBME-1 showed no advantage over TPO or DPP4. [ABSTRACT FROM AUTHOR]

Background: Minimal access approaches are increasingly used in endocrine surgery. Several minimal access approaches to the thyroid gland have been described, including a small-incision lateral approach and a video-assisted central approach, but to date no technique has been universally accepted.Methods: Benefiting from the experience of more than 500 endoscopic parathyroidectomies via a lateral neck approach, the authors developed an endoscopic thyroidectomy based on the same approach and principles. Patients with solitary nodules smaller than 3 cm in diameter and no history of neck surgery or irradiation were offered this operation. A detailed description of the surgical technique is provided.Results: Of the 742 thyroidectomies performed in 2004, 38 (5.1%) were endoscopic thyroidectomies. The mean nodule size was 22-mm (range, 7-47-mm), and the mean operating time was 99 min (range, 64-150-min). In all cases, the recurrent laryngeal nerve was preserved intact, and the superior and inferior parathyroids were identified, respectively, in 36 and 33 of the 38 patients. Two patients required conversion to an open cervicotomy. All patients were discharged the day after surgery.Conclusions: The described endoscopic lateral approach combines the coherence of the minimal access lateral approach and the benefits of fiberoptic magnification. It is a safe and effective technique in the hands of an appropriately trained surgeon. [ABSTRACT FROM AUTHOR]

The efficiency of conventional fossil power plants is a strong function of the steam temperature and pressure. Research to increase both has been pursued worldwide, since the energy crisis in the 1970s. The need to reduce CO2 emissions has recently provided an additional incentive to increase efficiency. More recently, interest has also been evinced in advanced combustion technologies utilizing oxygen instead of air for combustion. The main enabling technology in achieving the above goals is the development of stronger high temperature materials. Extensive research-and-development programs have resulted in numerous high-strength alloys for heavy section piping and for tubing needed to build boilers. The study reported on here is aimed at identifying, evaluating, and qualifying the materials needed for the construction of the critical components of coal-fired boilers that are capable of operating with steam at temperatures of 760 °C (1400 °F) and pressures of 35 MPa (5000 psi). The economic viability of such a plant has been explored. Candidate alloys applicable to various ranges of temperatures have been identified. Stress rupture tests have been completed on the base metal and on welds to a number of alloys. Steamside oxidation tests in an autoclave at 650 °C (1200 °F) and 800 °C (1475 °F) have been completed. Fireside corrosion tests have been conducted under conditions simulating those of waterwalls and superheater/ reheater tubes. The weldability and fabricability of the alloys have been investigated. The capabilities of various overlay coatings and diffusion coatings have been examined. This article provides a status report on the progress achieved to date on this project. [ABSTRACT FROM AUTHOR]

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Methods: A videoscopic parathyroidectomy was performed in 22 patients presenting with primary hyperparathyroidism (PHPT). No patient had undergone previous neck surgery, presented with goiter or had a history of familial PHPT. Ultrasonography and Sestamibi scanning were performed preoperatively. Rapid intact parathormone assay was used during surgery. Through a 15-mm transversal skin incision on the anterior border of the sternocleidomastoid muscle (SCM), the fascia connecting the lateral portion of the strap muscles and the thyroid lobe with the carotid sheath was gently divided, far enough to visualize the prevertebral fascia. Once enough space was created, three trocars were inserted: a 12-mm trocar through the incision and two 2.5-mm trocars on the line of the anterior border of the SCM, above and below the first trocar. Carbon dioxide was insufflated to 8 mmHg. Unilateral video-assisted parathyroid exploration was then carried out using a 10-mm O° endoscope. Once the adenoma had been identified, the trocars were removed. Then, directly through the skin incision, the thyroid lobe was retracted medially and the adenoma was extracted after clipping its pedicle. Results: Among the 23 enlarged glands, 20 (80%) were correctly identified by endoscopic exploration: mean weight 843 mg (100 mg to 5 g). The exploration was unilateral in 17 patients but bilateral in 5. Mean time of unilateral endoscopic exploration was 84 min (40–130 min). Morbidity was represented by two superficial hematomas. All 22 patients were biochemically cured, follow-up ranging from 3 months to 14 months. Conclusions: This preliminary study demonstrates that minimally invasive videoscopic parathyroidectomy by lateral approach is a feasible surgical procedure. [ABSTRACT FROM AUTHOR]

Introduction: Laparoscopic adrenalectomy (LA) is safe and effective for small, benign, functioning tumors. Whether it should be performed for other adrenal tumors is questionable. The aim of this study was to evaluate and compare the complications and results of 150 consecutive LAs performed either for small benign tumors or for large and/or potentially malignant tumors. Methods: Between June 1994 and August 1998, we performed 150 LAs in 142 patients. We used a transperitoneal flank approach in the lateral decubitus position. Initially, our indications for LA were limited to small (<4 cm) benign tumors (group I, n=102): 56 aldosteronomas, 33 Cushing’s syndrome, 11 pheochromocytomas and 2 nonfunctional tumors. Progressively, based on increasing experience, LA was also proposed for tumors larger than 4 cm or potentially malignant (group II, n=48): 5 Cushing’s syndrome, 1 androgen-producing tumor, 14 pheochromocytomas and 28 nonfunctional tumors. Preoperative demonstration of invasive extra-adrenal carcinoma remained an absolute contraindication for LA. Results: Mean tumor size was 21.1 mm in group I and 51.6 mm in group II. All tumors in group I were benign. Six of the 48 tumors in group II were malignant (12.5%). The rate of complication was, respectively, 7.8% and 8.3% in groups I and II. The rate of conversion was, respectively, 4.9% and 6.2% in groups I and II. Mean operative time was 131 min in group I and 129 min in group II. The endocrinopathy was cured in all patients. To date, no recurrences have been observed. Conclusions: LA can be proposed for large (<12 cm) or potentially malignant adrenal tumors provided preoperative investigations have not demonstrated invasive carcinoma. An open procedure should be performed instead if local invasion is observed at the start of the operation. [ABSTRACT FROM AUTHOR]

Human platelets have been shown to possess high-affinity binding sites for H-imipramine. These binding sites have a similar affinity and drug specificity to those already described in rat brain. The platelets from healthy volunteers show no difference in H-imipramine binding between the sexes but there is a decrease in maximal H-imipramine binding with increasing age of the donor. [ABSTRACT FROM AUTHOR]

The benefits of prophylactic central neck dissection (PCND) in patients with papillary thyroid carcinoma (PTC) have not been clearly demonstrated so far and should be weighed against the potential risks of the procedure. The aim of the study was to assess the recurrent laryngeal nerve and parathyroid risks of PCND after total thyroidectomy in patients with PTC and to compare the results with those obtained in patients who underwent total thyroidectomy only. Methods: We selected 100 patients who underwent a total thyroidectomy: 50 for nontoxic benign multinodular goiter (Group 1) and 50 for PTC (Group 2). Patients with PTC had no evidence of macroscopic lymph node invasion during surgery and underwent, in addition to the total thyroidectomy, a PCND. All of the 100 patients were operated on by two experienced endocrine surgeons. All patients had pre- and postoperative investigations of vocal cord movements. Calcemia and phosphoremia were systematically evaluated preoperatively and on day 1 and day 2 after surgery. All patients presenting a postoperative calcemia below 1.90 mmol/l were considered to present an early postoperative hypoparathyroidism and received calcium-vitamin D therapy. The hypoparathyroidism was considered permanent when calcium-vitamin D therapy was still necessary 1 year after surgery. Results: None of the patients presented permanent nerve palsy. There were three cases of transient nerve palsy (6%) in Group 1 and two (4%) in Group 2. In Group 1 there was no permanent hypoparathyroidism and four cases of transient hypoparathyroidism (8%). In Group 2, seven patients presented transient hypoparathyroidism (14%) and two patients (4%) remained with definitive hypoparathyroidism. Conclusion: After total thyroidectomy for PTC, PCND does not increase recurrent laryngeal nerve morbidity but it is responsible for a high rate of hypoparathyroidism, especially in the early postoperative course. Even taking into account the possible benefits, the results make it difficult to advocate PCND as a routine procedure in all patients presenting a PTC. [ABSTRACT FROM AUTHOR]