EVALUATION OF CONDUCTIVE HEAT TRANSFER MECHANISMS BETWEEN AN IMMERSED SURFACE AND THE ADJACENT LAYER OF PARTICLES IN BUBBLING FLUIDIZED BEDS

The evaluation of the heat transfer coefficient h_wp between a heat exchanging surface immersed in a gas fluidized bed and the adjacent layer of dense phase particles is analyzed in this contribution. Gas convective and radiant effects are not included in the present analysis.

The inclusion of h_wp, or an equivalent formation, in mechanistic models describing heat transfer has been necessary because the sudden voidage variation close to the immersed wall restrains significantly the heat transfer rate. However, there is not at present a widely accepted expression to evaluate h_wp.

A precise formulation for h_wp accounting for transient conduction inside spherical particles, the Smoluchowski effect, the concentration of particles in the adjacent layer (N_p) and an effective separation gap (l₀) is developed here.

Although N_p can be estimated, in principle, from experimental evidence in packed beds, and it is reasonably expected that l₀ = 0, the analysis of experimental heat transfer rates in moving beds, packed beds, and bubbling fluidized beds indicate that values of h_wp are, in general, smaller than expected from these assumptions. Appropriate values of l₀ and N_p are then stimated by fitting the experimental data.

The probable effect of surface asperities is also discussed by analyzing a simplified geometrical model. It is concluded that the parameter l₀ can be also effective to account for particle roughness, independently of thermal properties.     

Hepatitis C. Issues for women and their partners

OBJECTIVE: To evaluate the diagnostic accuracy of transvaginal ultrasonography in detecting and measuring free pelvic fluid. STUDY DESIGN: Eighty-two patients undergoing diagnostic or therapeutic laparoscopy at a tertiary care center were prospectively assessed before surgery by transvaginal ultrasound. Free pelvic fluid was measured in two ultrasonographic planes. These measurements were compared to the volume of fluid aspirated during laparoscopy. RESULTS: The mean volumes reported for transvaginal ultrasound were significantly lower than those observed at laparoscopy (mean milliliters +/- SEM, 2.54 +/- 0.5 versus 9.42 +/- 1.3, P < .001). The smallest volume of free pelvic fluid that was consistently detected by ultrasound was 8 mL. Whenever no fluid or < 1 mL was detected by transvaginal ultrasound, a small volume of fluid was found at laparoscopy (mean milliliters +/- SEM, 1.6 +/- 0.47). The sensitivity of transvaginal ultrasound was 83% and specificity was 69%. CONCLUSION: Transvaginal ultrasound is a sensitive method of detecting the presence of > 8 mL of free pelvic fluid and therefore is an important diagnostic tool in the assessment of pelvic pathology associated with increased peritoneal fluid.     

The inv dup(15) syndrome: a clinically recognizable syndrome with altered behavior, mental retardation, and epilepsy

The most common of the heterogeneous group of the extra structurally abnormal chromosomes (ESACs) is the inv dup(15), whose presence results in tetrasomy 15p and partial tetrasomy 15q. Inv dup(15), containing the Prader-Willi/Angelman syndrome (PWS/AS) region, are constantly associated with phenotypic abnormalities and mental retardation. We report on four additional patients with inv dup(15), whose behavioral pattern, and neurologic and physical findings further delineate the phenotype of this neurogenetic syndrome. We also provide FISH analyses on chromosomes of the observed ESACs and discuss the role of a number of genes located within the tetrasomic region.     

Optimisation of antioxidant activity of grape cane extracts using response surface methodology

Solid–liquid extraction and response surface methodology were used to optimise conditions for the antioxidant activity of grape cane extracts. The independent processing variables were ethanol concentration, temperature and solvent to solid ratio. Ethanol concentration and temperature significantly affected antioxidant activity measured by the Trolox equivalent antioxidant capacity (TEAC) assay and the oxygen radical absorbance capacity using fluorescein (ORAC_FL) method (p  0.01), whereas the solvent to solid ratio did not significantly affect the activity (p > 0.05). Antioxidant activity of the extracts, determined by the TEAC assay, varied from 85.6 to 238.6 μmol Trolox equivalents/g of dry sample. ORAC_FL values ranged from 308.4 to 1302.7 μmol Trolox equivalents/g of dry sample. Ethanol concentrations of 40.4% and 55.4% were optimal for the highest antioxidant activities measured by the TEAC assay and the ORAC_FL method, respectively. The optimal temperature was 83.6 °C. Antioxidant activity correlates with total phenolic content of extracts.     

A particulate model of solid waste incineration in a fluidized bed combining combustion and heavy metal vaporization

This study aims to develop a particulate model combining solid waste particle combustion and heavy metal vaporization from burning particles during MSW incineration in a fluidized bed. The original approach for this model combines an asymptotic combustion model for the carbonaceous solid combustion and a shrinking core model to describe the heavy metal vaporization. A parametric study is presented. The global metal vaporization process is strongly influenced by temperature. Internal mass transfer controls the metal vaporization rate at low temperatures. At high temperatures, the chemical reactions associated with particle combustion control the metal vaporization rate. A comparison between the simulation results and experimental data obtained with a laboratory-scale fluid bed incinerator and Cd-spiked particles shows that the heavy metal vaporization is correctly predicted by the model. The predictions are better at higher temperatures because of the temperature gradient inside the particle. Future development of the model will take this into account.     

Natural selection of academic papers

Academic papers, like genes, code for ideas or technological innovations that structure and transform the scientific organism and consequently the society at large. Genes are subject to the process of natural selection which ensures that only the fittest survive and contribute to the phenotype of the organism. The process of selection of academic papers, however, is far from natural. Commercial for-profit publishing houses have taken control over the evaluation and access to scientific information with serious consequences for the dissemination and advancement of knowledge. Academic authors and librarians are reacting by developing an alternative publishing system based on free-access journals and self-archiving in institutional repositories and global disciplinary libraries. Despite the emergence of such trends, the journal monopoly, rather than the scientific community, is still in control of selecting papers and setting academic standards. Here we propose a dynamical and transparent peer review process, which we believe will accelerate the transition to a fully open and free-for-all science that will allow the natural selection of the fittest ideas.     

Metabolic changes during recovery in normothermic versus hypothermic patients undergoing surgery and receiving general anesthesia and epidural local anesthetic agents

BACKGROUND: Mild hypothermia is accompanied by metabolic changes. Epidural local anesthetic agents attenuate the surgical stress response, but it is not known whether they modulate thermal stress. METHODS: Thirty patients undergoing colorectal surgery, performed by one surgical team, received epidural 0.5% bupivacaine to achieve T3-S5 sensory block. They were then assigned randomly to two groups of 15 patients each. The control or unwarmed group was left to cool during surgery, whereas active warming was used in the warmed group. General anesthesia was induced by thiopentone, vecuronium, fentanyl, nitrous oxide in oxygen, and enflurane. At the end of surgery, both groups received epidural 0.25% bupivacaine to maintain a T5-L3 sensory block. Aural canal (core) and skin surface (15 sites) temperatures; oxygen consumption; pain visual analogue score; and concentrations of epinephrine, norepinephrine, glucose, cortisol, lactate, and free fatty acids in plasma were measured before epidural blockade, 30 min after epidural blockade, at the end of surgery, and for 4 h after surgery. Patients and those measuring the outcomes were unaware of group allocation. RESULTS: Core and mean skin temperatures decreased significantly in the control group (P < 0.001) but not in the warmed group. Catecholamine concentrations in plasma decreased significantly after epidural block, and although concentration of epinephrine in plasma increased from baseline sharply in the control group at the end of surgery (P = 0.004), it decreased in the warmed group (P = 0.007). During recovery, there was no difference between the two groups for norepinephrine concentrations in plasma, body weight-adjusted oxygen consumption, pain visual analogue score, and metabolites. CONCLUSIONS: The postoperative metabolic changes obtained with epidural block were similar except for an attenuated concentration of epinephrine in normothermic patients compared with those who were mildly hypothermic.     

CMOS pixels for subretinal implantable prothesis

This work reports on the design, fabrication, and characterization of CMOS pixels for subretinal implants, which seems to be an effective way to recover visual capabilities in some types of blindness. Two possible approaches are presented for CMOS pixel implementation: 1) an approach based on a light-controlled oscillator (LICOS) using a ring oscillator with an odd number of inverters and 2) an approach based on distributing a square signal at each pixel that filters out a number of pulses depending of the light intensity wave across the chip (WATCH). Both types of pixels fabricated in 0.35-/spl mu/m CMOS demonstrate good mimic of the electrical behavior of human retina, with low-power consumption (typically 1 mW for a 14/spl times/14 matrix of pixels) and having small dimensions (75/spl times/78.5 /spl mu/m/sup 2/ for LICOS and 70/spl times/50 /spl mu/m/sup 2/ for WATCH), which make them suitable for practical implants. Experimental validation is reported on physiological solutions. Because of its characteristic, the proposed matrix of pixels could be considered as one of the first stand-alone highly integrated solutions for subretinal implant chips.