bluuebunny/crossref_metadata_2025 huggingface dataset:
Cholera Toxin Inhibitors Studied with High‐Performance Liquid Affinity Chromatography: A Robust Method to Evaluate Receptor–Ligand Interactions
Authors: Bergström Maria , Liu Shuang , Kiick Kristi L. , Ohlson Sten
Published: December 2008

Anti‐adhesion drugs may be an alternative to antibiotics to control infection of micro‐organisms. The well‐characterized interaction between cholera toxin and the cellular glycolipid GM1 makes it an attractive model for inhibition studies in general. In this report, we demonstrate a high‐performance liquid affinity chromatography approach called weak affinity chromatography to evaluate cholera toxin inhibitors. The cholera toxin B‐subunit was covalently coupled to porous silica and a (weak) affinity column was produced. The KD values of galactose and meta‐nitrophenyl α‐d‐galactoside were determined with weak affinity chromatography to be 52 and 1 mm, respectively, which agree well with IC50 values previously reported. To increase inhibition potency multivalent inhibitors have been developed and the interaction with multivalent glycopolypeptides was also evaluated. The affinity of these compounds was found to correlate with the galactoside content but KD values were not obtained because of the inhomogeneous response and slow off‐rate from multivalent interactions. Despite the limitations in obtaining direct KD values of the multivalent galactopolypeptides, weak affinity chromatography represents an additional and valuable tool in the evaluation of monovalent as well as multivalent cholera toxin inhibitors. It offers multiple advantages, such as a low sample consumption, high reproducibility and short analysis time, which are often not observed in other methods of analysis.
Cationic Amphiphilic Polyproline Helices: Side‐Chain Variations and Cell‐Specific Internalization
Authors: Geisler Iris , Chmielewski Jean
Published: December 2008

Cell‐penetrating peptides present an attractive and efficient tool for the delivery of a variety of cell impermeable cargoes across the cellular membrane. Cell‐penetrating peptides usually consist of short basic peptide sequences that are internalized by a variety of cell lines. Most cell‐penetrating peptides lack cell specificity, however, which greatly limits their use as efficient therapeutic agents. Herein, we present two cell‐penetrating peptides displaying a type II polyproline helical backbone that are functionalized to contain six cationic moieties and two distinctive hydrophobic functionalities, namely isobutyl or benzyl groups. The uptake efficiency of these cationic amphiphilic polyproline helices was studied in seven different cell lines, six cancerous (MCF‐7, HOS, HT1080, HeLa, KB‐FD, KB3‐1) and one non‐cancerous (WI 38). The cationic amphiphilic polyproline helix P11LRR at 50 μm showed high specificity toward MCF‐7 breast cancer cells. Co‐culture experiments with P11LRR demonstrated almost exclusive internalization by MCF‐7 cells and not WI38. The replacement of the isobutyl hydrophobic group with a benzyl moiety resulted in a shift in uptake efficiency and specificity across some cell lines. These results demonstrate that the type of hydrophobic residues utilized in the creation of cell‐penetrating peptides can strongly influence the extent and specificity of cellular internalization.
Possible common central pathway for resistin and insulin in regulating food intake
Authors: Cifani C. , Durocher Y. , Pathak A. , Penicaud L. , Smih F. , Massi M. , Rouet P. , Polidori C.
Published: December 2008

Aim:  Adipose tissue has been the object of intense research in the field of obesity and diabetes diseases in the last decade. Examination of adipocyte‐secreted peptides led to the identification of a unique polypeptide, resistin (RSTN), which has been suggested as a link between obesity and diabetes. RSTN plays a clearly documented role in blocking insulin (INS)‐induced hypoglycaemia. As brain injection of INS affects feeding behaviour, we studied the possible interaction between INS and RSTN in food‐deprived rats, measuring effects on food intake. In addition, we examined how RSTN might affect neuropeptide Y (NPY)‐induced feeding, as studies have shown that rat RSTN can interfere with the NPY system.

Methods:  Overnight food‐deprived rats were injected into the third brain ventricle (3V) with either INS (10 or 20 mUI), RSTN (0.1–0.4 nmol/rat), or saline before access to food. Another group of rats was injected into the 3V with RSTN alone, NPY alone or RSTN plus NPY. Their food intake and body weight were measured.

Results:  Our results confirm the hypophagic effect of RSTN on food deprivation‐induced food intake, and more importantly, show that RSTN neither potentiates nor blocks the effects of INS on food intake, but does reduce the hyperphagic effect of NPY.

Conclusion:  The observation that RSTN does not modify feeding INS‐induced hypophagia, but does influence NPY‐induced feeding, points to the possibility that RSTN may be involved in control of food intake through an NPY‐ergic mechanism as INS.
Indoor environment in three North European cities in relationship to atopy and respiratory symptoms
Authors: Gunnbjörnsdóttir María Ingibjörg , Norbäck Dan , Björnsson Eythor , Soon Argo , Jarvis Deborah , Jõgi Rain , Gislason David , Gislason Thorarinn , Janson Christer
Published: December 2008

Background:  In the European Community Respiratory Health Survey (ECRHS) I, the lowest prevalence of asthma and atopy was found in Reykjavík (Iceland) and Tartu (Estonia). The aim of this study was to compare home environments in Reykjavík and Tartu to a town with a higher prevalence of asthma and atopy (Uppsala, Sweden) in an attempt to identify factors in the indoor environment that could explain these differences.

Method:  A random sample of 129 ECRHS II participants was included in this analysis at each of the three study centres. The subjects answered a questionnaire, blood was analysed for specific immunoglobulin E, a methacholine test was performed and home indoor measurements were taken.

Results:  The prevalence of atopy was 11.9% in Reykjavík, 35.5% in Uppsala and 28.2% in Tartu (P < 0.04). The level of indoor cat allergen was significantly lower in Reykjavík compared with Uppsala (P = 0.05). No mite allergens were identified in the 41 homes investigated in Reykjavík, while this was the case in 16% and 72% of the households in Uppsala and Tartu, respectively (P = 0.001). A positive association was found between asthma symptoms and cat allergen levels [odds ratio 1.53 (95% confidence interval 1.04–2.24)], while the levels of viable moulds were significantly associated with increased bronchial responsiveness.

Conclusions:  Indoor exposure to allergens, moulds and bacteria was lower in Reykjavík than in the Swedish and Estonian centres. This finding indicates that the lower prevalence of allergic sensitization in Reykjavík may partly be related to lower indoor allergen exposure.

Please cite this paper as: Gunnbjörnsdóttir MI, Norbäck D, Björnsson E, Soon A, Jarvis D, Jõgi R, Gislason D, Gislason T and Janson C. Indoor environment in three North European cities in relationship to atopy and respiratory symptoms. The Clinical Respiratory Journal 2009; 3: 85–94.
Repaglinide‐loaded long‐circulating biodegradable nanoparticles: Rational approach for the management of type 2 diabetes mellitus
Authors: JAIN Shelesh , SARAF Swarnlata
Published: December 2008

Background:  Repaglinide (RPG) is an oral hypoglycemic agent with excellent bioavailability (90–98%) and a short plasma half‐life (2–6 h). A full dose of RPG is required before each meal; hence, therapy may become inconvenient. Thus, the aim of the present study was to design a novel delivery system to maintain peak plasma levels of RPG for the long‐term management of diabetes mellitus.

Methods:  Two nanoparticle formulations were prepared by combining RPG with poly (lactic‐co‐glycolic) acid alone or as a copolymer with methoxypolyethylene glycol (RPGNP1 and RPGNP2, respectively); both formulations were subjected to in vitro and in vivo characterization. In vivo characterization was performed in a streptozotocin (STZ)‐induced diabetic male albino rats.

Results:  The mean particle size of the RPGNP1 and RPGNP2 formulations was 387.8 ± 11.9 and 310.2 ± 12.4 nm, respectively, with a zeta potential of −27.4 ± 0.7 and −15.7 ± 0.5 mV, respectively. The entrapment efficiency and drug content of RPGNP1 (58.7 ± 1.3% and 27.4 ± 2.3%, respectively) was better than that of RPGNP2 (45.8 ± 1.2% and 24.3 ±1.1%, respectively). Blood glucose levels of RPGNP1‐ and RPGNP2‐treated STZ‐diabetic rats were reduced significantly (to normal levels) compared with untreated STZ‐diabetic rats (P < 0.05), but there was no difference between the two treatment groups (P > 0.05). However, whereas RPGNP1 was effective for a period of only 24 h, RPGNP2 was effective for up to 1 week.

Conclusions:  The results of the present study show that RPGNP2 effectively manages type 2 diabetes mellitus for up to 1 week. Surface‐modified NPs could be used to improve patient compliance with drug treatment as a result of decreased dosing frequency.
Exercise test and glucose homeostasis in rats treated with alloxan during the neonatal period or fed a high calorie diet
Authors: CONTARTEZE Ricardo Vinícius Ledesma , de Alencar MOTA Clécia Soares , de OLIVEIRA Camila Aparecida Machado , de Almeida LEME José Alexandre Curiacos , BOTTCHER Lara Belmudes , de MELLO Maria Alice Rostom , LUCIANO Eliete
Published: December 2008

Background: Animal models appear well‐suited for studies into the role of exercise in the prevention of non‐insulin‐dependent diabetes mellitus (NIDDM). The aim of the present study was to analyze glucose homeostasis and blood lactate during an exercise swimming test in rats treated with alloxan during the neonatal period and/or fed a high calorie diet from weaning onwards.

Methods: Rats were injected with alloxan (200 mg/kg, i.p.) or vehicle (citrate buffer) at 6 days of age. After weaning, rats were divided into four groups and fed either a balanced diet or a high‐caloric diet as follows: C, control group (vehicle + normal diet); A, alloxan‐treated rats fed the normal diet; H, vehicle‐treated rats fed the high‐caloric diet; and HA, alloxan‐treated rats fed the high‐caloric diet.

Results: Fasting serum glucose levels were higher in groups A and AH compared with the control group. The Homeostatic Model Assessment index varied in the groups as follows: H>A>HA = C. There were no differences in free fatty acids or blood lactate concentrations during the swim test.

Conclusions: Alloxan‐treated rats fed a normal or high‐caloric diet have the potential to be used in studies analyzing the role physical exercise plays in the prevention of NIDDM.
Index of myocardial performance in patients with type 2 diabetes without hypertension and its relationship with clinical and echocardiographic parameters
Authors: SAGLAM Hayrettin , SEYFELI Ergun , GUL Ibrahim , DURU Mehmet , GOKCE Cumali
Published: December 2008

Background:  Diabetes mellitus affects the systolic and diastolic function of the left ventricle (LV). The aim of the present study was to evaluate the index of myocardial performance (IMP), a new Doppler index, in asymptomatic, normotensive patients with type 2 diabetes mellitus (T2DM).

Methods:  The study population consisted of 40 asymptomatic normotensive patients with T2DM (22 women, 18 men; mean [±SD] age 49 ± 7 years) and 20 healthy controls (13 women, seven men; mean age 45 ± 4 years). M‐Mode and two‐dimensional Doppler echocardiography was performed in all subjects to calculate IMP. Venous blood samples were collected for analysis and body mass index (BMI) was calculated.

Results:  In normotensive T2DM patients, the mitral E wave was decreased, whereas mitral A wave, mitral E/A ratio, and septal wall thickening were increased compared with values obtained for the control group. The IMP was higher in normotensive T2DM patients than in the control group (P = 0.004). There was a significant correlation between IMP and triglyceride (TG) levels (P < 0.001), mitral E wave (P < 0.001), mitral E/A ratio (P < 0.001), ejection fraction (P = 0.001), fasting blood glucose (P =0.007), LV systolic dimension (P < 0.001), duration of diabetes (P = 0.017), and BMI (P = 0.029). Stepwise multiple regression analysis demonstrated that only TG levels (β = 0.355, t = 2.487, P = 0.017) and the mitral E/A ratio (β = −0.384, t = −2.690, P = 0.011) had an independent effect on IMP.

Conclusion:  The results of the present study indicate that IMP is increased in normotensive T2DM patients. The findings suggest that increased IMP may be an early sign of diabetic cardiomyopathy in normotensive diabetic patients with preserved LV function.
Prevalence of metabolic syndrome and its association with obesity indices in a Chinese population
Authors: HUANG Yun , ZHAO Zhiyun , LI Xiaoying , WANG Jiguang , XU Min , BI Yufang , WANG Weiqing , LIU Jianmin , NING Guang
Published: December 2008

Background:  To investigate the prevalence of metabolic syndrome in an urbanizing community in Qingpu, a suburb of Shanghai, and to determine which obesity indices, including body mass index, waist circumference (WC), and waist:hip (WHpR), and waist:height (WHtR) ratios, are most closely associated with metabolic syndrome.

Methods:  We conducted a cross‐sectional health survey of 1634 individuals (age 15–87 years) in the Jinhulu community located in Qingpu. The National Cholesterol Education Program Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (NCEP ATP III) criteria were used to define metabolic syndrome, with central obesity defined according to Asia–Pacific (APC) region criteria.

Results:  The age‐standardized prevalence of metabolic syndrome was 3.6% in men and 7.2% in women. Using the criterion of central obesity in the APC, the age‐standardized prevalence of metabolic syndrome increased to 8.3% in men and 10.9% in women. Regardless of age, WHtR consistently showed a higher odd ratios (OR) after adjustment for confounding factors of 2.17 (95% confidence interval [CI] 1.12–4.20; P = 0.022) in subjects<52 years of age and 1.92 (95% CI 1.18–3.11; P = 0.008) in those ≥52 years of age. In men, the WHtR was the only significant predictor (OR 2.42; 95% CI 1.15–5.08; P = 0.02) of metabolic syndrome after adjustment, whereas in women WHtR (OR 1.87; 95% CI 1.37–2.85; P =0.0088) was slightly inferior to WHpR and WC.

Conclusion:  Metabolic syndrome is prevalent in an urbanizing rural area in Qingpu. Of the anthropometric parameters commonly used to identify metabolic syndrome, WHtR may be the best.
Sterilization in Alberta, 1928 to 1972: Gender Matters*
Authors: GREKUL JANA
Published: December 2008

En 1928, la province canadienne de l'Alberta a adopté une loi sur la stérilisation sexuelle et, jusqu'à son abrogation en 1972, plus de 2,800 personnes ont été stérilisées. De ce nombre, les femmes ont été surreprésentées. Cet article examine comment des regards changeants portés sur l'eugénique ont conduit à une transformation subtile d'où a émergé un système à deux volets qui a ciblé des hommes ayant une déficience mentale, souvent un danger pour la société, et des femmes normales du point de vue mental mais anormales moralement qui ont accepté la stérilisation. Le geste s'est avéré un succès en ce qui concerne le type et le nombre de personnes stérilisées, et la pérennité du programme.

Alberta, Canada, passed a Sexual Sterilization Act in 1928 and up until its repeal in 1972, over 2,800 people were sterilized. Women were overrepresented in the number of sterilizations performed. This paper explores how changing understandings of eugenics led to a subtle transformation which resulted in a “two‐pronged” system that targeted mentally defective men, often a danger to society, and mentally normal but morally abnormal women who consented to sterilization. The end result was success for the movement in terms of the types and numbers of people sterilized, and in the longevity of the program.
From Community to Public Safety Governance in Policing and Child Protection
Authors: DEUKMEDJIAN JOHN EDWARD , CRADOCK GERALD
Published: December 2008

L'interopérabilité grandissante entre le maintien de l'ordre et la protection de l'enfant au Canada et au Royaume‐Uni semble indiquer que nous nous trouvons au milieu d'un changement gouvernemental passant de la gouvernance communautaire à une gouvernance de la sécurité publique. En effet, les discours mettant l'accent sur l'expertise locale en maintien de l'ordre et en protection de l'enfant se sont grandement transformés en raison des critiques sur le manque d'interdépendance entre les organismes. Les deux pays ont maintenant créé des bases de données interinstitutionnelles pour la gestion des personnes à risque. Cette intégration administrative engendre différentes formes de réglementations. Les auteurs concluent leur article en soutenant que cet ethos émergeant peut être conceptualisé comme une rationalité gouvernementale naissante.

The growing interoperability between policing and child protection in Canada and the United Kingdom suggests that we are in the midst of a governmental shift from community governance to public safety governance. Indeed, discourses emphasizing local expertise in policing and child protection have largely muted because of criticisms over the lack of interagency interconnectedness. Both countries have now developed national interagency databases for the management of persons of risk. This institutional integration engenders different forms of regulation. We conclude by arguing that this emergent ethos may be conceptualized as a nascent governmental rationality.
Growth Kinetics and Wall Stress Effects in Sublimation Growth of AlN Bulk Crystals
Authors: Wu Bei , Ma Ronghui , Zhang Hui
Published: December 2008

In the sublimation crystal growth process, source materials sublime at a higher temperature, and the resulting vapor transports to the seed crystal at a lower temperature where surface reaction and crystallization takes place. We have developed a two-dimensional numerical model to simulate the thermal and fluid fields in an AlN bulk growth system. A growth model that incorporates thermodynamic analyses, Stefan flow or diffusion transport, and growth kinetics has been developed to predict the growth rate of AlN bulk crystal. In addition, a thermomechanical stress model has also been developed to predict the thermal stress evolution in an AlN crystal.
Continuous Silicon Wafer Manufacturing by EFG Method
Authors: Wang C. , Sun D. , Zhang H. , Zheng L. , Yang B.
Published: December 2008

A comprehensive two-dimensional numerical model, which accounts for heat/mass transfer, solidification, and electromagnetic field, has been developed to simulate the silicon tube growth by the Edge-defined film-fed (EFG) method. A multi-block grid system has been employed to yield a high accuracy in the vicinity of die tip with relatively low CPU time, and the solution procedure is satisfied the flux conservation at the block interface. Selected results of magnetic and temperature fields have been presented for the silicon tube growth system of 30cm in diameter and 0.3mm in thickness. Two local models have also been developed to study the effect of the size of window opening and tube thickness on the maximum growth rate using the inner and outer heater temperature profiles as boundary conditions.
Measurement of Thermal Conductivity of Carbon Foams
Authors: Alam M. K. , Druma A. M.
Published: December 2008

A number of carbon foam products are being developed for use as insulation, heat spreaders, and compact heat exchanger cores. The application of carbon foams in aerospace applications is advantageous due to the high thermal conductivity and low density of the graphitic foam. However, the measurement of thermal conductivity has been difficult due the problems of interface contact and lower strength of the foam. The flash diffusivity method has been used to find thermal conductivity of a wide range of materials. Because of the porous nature of the foam, errors may be introduced with the flash diffusivity method. An analytical and experimental study has been carried out to determine the validity of the flash diffusivity method for foam specimen.
Effects of a Flow Disturbing Plate on Pool Boiling Heat Transfer on a Vertical Tube
Authors: Kang Myeong-Gie
Published: December 2008

Effects of the width and location of a flow disturbing circular plate, installed at a vertical tube surface, on nucleate pool boiling heat transfer of water at atmospheric pressure have been investigated experimentally. Through the tests, changes in the degree of intensity of liquid agitation have been analyzed. The plate changes the fluid flow around the tube as well as heat transfer coefficients on the tube surface. It is identified that the plate width changes the rate of the circulating flow whereas its location changes the growth of the active agitating flow. Moreover, the flow chugging was observed at the downside of the plate.
Fast Computation of Microscale Temperature Distribution in LSI Chips
Authors: Hirasawa Shigeki , Isomura Satoru
Published: December 2008

A network method for quickly calculating the temperature distributions in an LSI chip with silicon-on-insulator (SOI) transistors and multi-layered lines has been developed. Its calculation time is less than 1/1000 of that of the finite element method, and its error is within 15%. The developed fast calculation method can be used in the case of more than 300 heating devices and more than 1000 lines in an LSI chip. It is thus a practical tool for designing the optimum layout of devices to prevent local temperature increases in an LSI chip.
A New Technique for Heat Flux Determination
Authors: Walker D. G. , Schetz J. A.
Published: December 2008

A new method for estimating heat fluxes from heating rate measurements and an approach to measure heating rates is proposed. Heating rate is defined as the time rate of change of the temperature. The example problem involves analytic heat conduction in a one-dimensional slab, where the measurement location coincides with the location of the estimated heat flux. The new method involves the solution to a Volterra equation of the second kind, which is inherently more stable than Volterra equations of the first kind. The estimates of the new approach are compared to typical inverse solution methods. The heating rate measurements are accomplished by leveraging the temperature dependent decay rate of thermographic phosphors. Results indicate that the new data-reduction method is far more stable than minimizing temperature residuals with errors of the order of the measurement noise.
Effects of Time Scale on Solutions of Inverse Heat Conduction Problems
Authors: Su Jian , Dong Hua
Published: December 2008

A wide variety of inverse heat conduction problems have been studied in the last two decades for the estimation of boundary or initial conditions, thermophysical properties, geometrical parameters, or heat source intensities. In most transient heat conduction problems, the mathematical models were cast in dimensionless forms, by using a diffusion time scale. As the thermal diffusivities are usually small, the physical time scales turn to be rather long. In this way, most works show that the inverse analysis yields satisfactory results, without addressing the implications of the physical time scale. The physical time scale, in fact, influences significantly the quality of the inverse solution. We present here a unified treatment for one-dimensional, linear inverse heat conduction problems using the conjugate gradient method with an adjoint equation, and also show that there are physical limitations by the time scale on the inverse solutions.
Improved Hybrid Solution of Conjugate Heat Transfer of Laminar Convection in Ducts With Axial Wall Conduction
Authors: Su Jian , de Castro Ana C. R.
Published: December 2008

This paper describes a hybrid analytical-numerical solution of conjugate heat transfer of laminar flow in a circular duct with axial wall conduction. An improved lumped-differential formulation is used to treat heat conduction in the wall; the Generalised Integral Transform Technique (GITT) is used to solve the energy equation in laminar flow. The coupled partial differential equations in the solid and fluid regions are reduced to a set of coupled ordinary differential equations. Analytical solution is obtained for a truncated set of ordinary differential equations. Improvement is expected over classical lumped models which are only applicable to problems with Biot numbers less than 0.1.
Heat Transfer Simulation Using PSpice
Authors: Li Shuhui , Challoo Rajab , McLauchlan Robert A.
Published: December 2008

Heat transfer considerations are important in almost all areas of technology. However, heat transfer analysis can be very difficult for complicated systems such as very large-scale integrated (VLSI) electric circuits and systems, making the simulation an attractive technique for studying heat transfer of those systems. This paper presents methods of heat transfer simulation using PSpice. First, typical heat transfer modes are discussed and heat transfer equations are presented. Then, equivalent electrical models are developed, and PSpice representations of those models are investigated. Finite-difference RC network models are developed and used for the simulation of complicated heat transfer problems using PSpice. Two typical heat transfer examples are studied. Simulations are performed to investigate and study the heat transfer and energy flow of the two examples using PSpice.
Numerical Simulation on Phase-Change Heat Transfer Within Microencapsulated Phase Change Material
Authors: Rao Yu , Lin Guiping
Published: December 2008

A source item-based computation model is developed for analysing phase-change heat transfer within Microencapsulated PCM suspending in a flowing carrier fluid to enhance convective heat transfer, with the consideration of phase-change temperature range and varying thermal properties. Solution is obtained by developing a control volume-based finite difference code, in which TDMA method combined with under-relaxation is used to solve a strong nonlinear equation. The code developed for this study can be used for evaluating Microencapsulated PCM suspension and instructing the preparation of Microencapsulated PCM.
Numerical Simulation of Infiltration of Carbon Fiber Preform in MMC Casting With Thermal Management
Authors: Lee E. K. , Amano R. S. , Rohatgi P. K.
Published: December 2008

In the casting of metal matrix composite, different processing parameters need to be controlled in order to promote the formation of primary alpha phase around the reinforcement. It has been shown [1–3] that when the reinforcement is allowed to be extended out of the cast mold and cooled by a heat sink, the microstructure of the composite can be improved due to faster heat extraction through the reinforcement. Thermal management of the reinforcement can eliminate a large portion of the eutectic phase during solidification, leading to an altered microstructure at the interface between the matrix and the reinforcement with the possibility of improved material properties. A companion paper [4] shows a comparison of the numerical simulation result of the casting of MMC by squeeze infiltration technique to the experimental work. The authors assumed that the solidification process started after the liquid metal has completely infiltrated the reinforcement. The simulation result gives a reasonable prediction to the experimentally measured cooling temperature profile. In this work, the effects of other processing parameters are analyzed to study the impregnation depth during squeeze infiltration. These processing parameters include the thermal conductivity of fibers, the initial (or preheat) mold temperature, the volume fraction of fibers, and the heat sink temperature. The study is based on the finite volume method for enthalpy formulated heat equation.
The Model of Mass and Heat Transfer in LPG Tanks Partially Exposed to Jet Fire
Authors: Xing Zhixiang , Jiang Juncheng
Published: December 2008

This paper describes a mathematical model developed to study the behavior of LPG tanks when subjected to jet fire. The model consists of a number of field and zone sub-models which are used to simulate the various physical phenomena taking place during the tank engulfment period. The comparisons between the model predicted results and the test data showed better agreement. The results showed that the jet fire partially impingement on tank wall led to higher wall temperatures and the time to failure was shorter than in engulfing pool fire. And the fire exposure started at the vapor wall is under more dangerous situation than the fire exposure at the bottom of the tank.
Round Turbulent Thermals, Puffs, Starting Plumes and Starting Jets in Uniform Crossflow
Authors: Diez F. J. , Bernal L. P. , Faeth G. M.
Published: December 2008

The self-preserving properties of round turbulent thermals, puffs, starting plumes and starting jets, in unstratified and uniform crossflow, were investigated experimentally. The experiments involved dye-containing fresh water (for nonbuoyant flows) and salt water (for buoyant flows) sources injected vertically downward into crossflowing fresh water within a water channel. Time-resolved video images of the flows were obtained using CCD cameras. Experimental conditions were as follows: source exit diameters of 3.2 and 6.4 mm, source Reynolds numbers of 2,500–16,000, source/ambient velocity ratios of 4–35, source/ambient density ratios (for buoyant flows) of 1.073 and 1.150, volumes of injected source fluid (for thermals and puffs) comprising 16–318 source diameters, streamwise (vertical) penetration distances of 0–200 source diameters and 0–13 Morton length scales (for buoyant flows) and crosstream (horizontal) penetration distances of 0–620 source diameters. Near-source behavior varied significantly with source properties but the flows generally became turbulent for streamwise distances within 5 source diameters from the source and became self-preserving for streamwise distances from the source greater than 40–50 source diameters. Crosstream motion satisfied the no-slip convection approximation. Streamwise motion for self-preserving conditions satisfied the behavior of corresponding self-preserving flows in still fluids: round thermals and puffs in still fluids for round thermals and puffs in crossflow and two-dimensional line thermals and puffs in still fluids for round starting plumes and jets in crossflow. The no-slip convection approximation for crossflow motion combined with self-preserving approximations for streamwise motion was also effective for predicting flow trajectories at self-preserving conditions for steady round turbulent plumes and jets in crossflow.
Numerical Investigation of Single Bubble Dynamics During Nucleate Boiling in Aqueous Surfactant Solutions
Authors: Zhang Juntao , Manglik Raj M.
Published: December 2008

The dynamics of a single growing and departing bubble during nucleate boiling from a horizontal heated surface in an aqueous surfactant solution has been numerically simulated. The full Navier-Stokes equations together with the bulk transport and adsorption-desorption-controlled surfactant interfacial transport equations are solved. A PDE-based fast local level-set method is used to computationally capture the vapor-liquid interface, and the dynamic surface tension is modeled as a body force on the interface. A second-order projection method along with a third-order ENO (essentially non-oscillatory) scheme for differencing the convection terms are applied for solving the momentum equation. The time discretization is dealt with a high order Runge-Kutta method. The multigrid preconditioned conjugate method (MPCG) is employed to solve the projection, which has strongly discontinuous coefficients caused by the physical properties jump across the vapor-liquid interface. The results illustrate the altered bubble dynamics in aqueous surfactant solutions, and their role in enhancing heat transfer.
Two-Phase Flow and Heat Transfer in Rectangular Micro-Channels
Authors: Qu Weilin , Yoon Seok-Mann , Mudawar Issam
Published: December 2008

Knowledge of flow pattern and flow pattern transitions is essential to the development of reliable predictive tools for pressure drop and heat transfer in two-phase micro-channel heat sinks. In the present study, experiments were conducted with adiabatic nitrogen-water two-phase flow in a rectangular micro-channel having a 0.406 × 2.032 mm cross-section. Superficial velocities of nitrogen and water ranged from 0.08 to 81.92 m/s and 0.04 to 10.24 m/s, respectively. Flow patterns were first identified using high-speed video imaging, and still photos were then taken for representative patterns. Results reveal that the dominant flow patterns are slug and annular, with bubbly flow occurring only occasionally; stratified and churn flow were never observed. A flow pattern map was constructed and compared with previous maps and predictions of flow pattern transition models. Annual flow is identified as the dominant flow pattern for conditions relevant to two-phase micro-channel heat sinks, and forms the basis for development of a theoretical model for both pressure drop and heat transfer in micro-channels. Features unique to two-phase micro-channel flow, such as laminar liquid and gas flows, smooth liquid-gas interface, and strong entrainment and deposition effects are incorporated into the model. The model shows good agreement with experimental data for water-cooled heat sinks.
Simulation Study of Heated Soil Vapor
Authors: Jadhav R. S. , Amano R. S. , Jatkar J. , Lind R. J.
Published: December 2008

Soil remediation using Heated Soil Vapor Extraction System has gained a significant attention in recent years. The process, developed by Advanced Remedial Technology**, comprises of a heat well (heat source) and an extraction well (sink). These wells are pipes, which are implanted in the soil. Heating is accomplished by circulating hot oil through the heat exchange units in heat well. The extraction well has a blower, which sucks the air, and other volatile gases that are evaporated due to heating. An analysis aimed at improving the predictability of the process using numerical tools has been carried out. The key parameters in the process can be identified as the distance between the wells, the temperature that has to be maintained in the heat well and the time required vaporizing the gases and taking them off the soil. These parameters are strongly dependent on the properties of the soil and properties of the chemical pollutants present in the soil. An attempt has been made to model the real process of heating the soil and vaporizing of chemicals in the soil. Such comprehensive analysis will be very much helpful in predicting the different parameters as discussed above and result in increase in effectiveness and efficiency of the process.
Thermal Curing and Strength of PMMA Bone Cement
Authors: Sanchez M. A. , Sutton W. , Rizk W. , Tompkins J.
Published: December 2008

Many current bone cements have proprietary minor ingredients that affect the chemical kinetics and heat transfer modeling of the exothermic reaction during bone cement polymerization. In addition, the geometry and the method of cooling/curing the bone cement can vary by application. A method for modeling energy generation, based on temperature measurement of various geometries and conditions, expresses the exothermic reaction and the duration with respect to time. Reaction from the bone cement can yield temperatures above 110°C for the air convective cooling boundary condition. Experiments show that by using cold irrigation cooling (saline) with an initial temperature of 1.5°C, the maximum reaction temperature of the PMMA cement approaches 40°C depending upon the thickness of the cement. For bone cement cooled in air and saline at room temperature, the exothermic reaction begins around 400 seconds (8 min) after the compounds are mixed. When cold saline is applied, the time-delay of the reaction is approximately 300 additional seconds compared to the two room temperature cases. Finally, based on compression testing, the structural behavior of the PMMA cement is improved when the material is cured in a slower and wet environment.
Ultrafast Laser-Induced Breakdown Spectroscopy and Application to Real-Time Control of Ultrafast Laser Micromachining Process
Authors: Tong Tao , Li Jinggao , Longtin Jon P.
Published: December 2008

A significant obstacle in ultrafast laser micromachining of multi-layer or heterogeneous micro-structures is the lack of an online diagnostic method to determine which material is being ablated during the material removal process. This problem arises because ultrafast lasers are generally insensitive to the material being processed. One promising technique to address this problem is the use of laser-induced breakdown spectroscopy (LIBS) by which the plasma generated during the laser-material interaction can be collected and analyzed to provide information regarding the elemental composition of the mate-rial being ablated. In this work, a real-time feedback control system for the ultrafast laser micromachining process based on the LIBS technique is built. The ultrafast LIBS signal is first characterized to prove the feasibility. Characteristics of spectral emission, temporal evolution, spatial heterogeneity of the ultrafast LIBS signal, effects from laser machining factors, etc., are discussed. Comparison methods for identifying the material emission patterns are then studied. Effective algorithms from the study are implemented into the control system software, SPECOMP, developed in the laboratory. Issues on the real-time control process are discussed. The real-time controlled machining process has then been applied to the machining of micro-structures on thermal sprayed material. Compared to the passive machining process without any such feedback control, SPECOMP system provides several important advantages including less damage to the substrate layer, shortened machining time, and more uniform feature sizes.
Ultrafast Laser Micromachining and Patterning of Thermal Spray Multilayers for Novel Sensor Fabrication
Authors: Chen Q. , Longtin J. P. , Sampath S. , Gambino R. J.
Published: December 2008

Fabrication of structural and functional parts and components, especially at the micro and nano scales, is crucial to a wide range of applications in the electronics, communications, medical, aerospace, and military industries. This work presents an innovative conformal direct-write technique for rapid prototyping and manufacturing novel sensors. The technique combines thermal spray, which, as an additive process, produces blanket depositions of films and coatings, with ultrafast laser micromachining, a subtractive process to produce functional patterns. Several kinds of sensing components, such as microheaters and strain gauges, have been successfully fabricated in this work with thermal spray technology and a femtosecond laser, which demonstrates the feasibility and advantages of the proposed technique. The electrical and thermal property characterization of the sensors was also performed, and shows promise for sensors in micro-sensing systems. With minor modification to pattern design and processing procedures, various sensing structures and electronic components, for example, precision resistors and interdigitated capacitors, can be readily fabricated using the presented technique.
Numerical Simulation of Thermal and Flow Characteristics Inside a Rod Type Cathode (RTC) Plasma Torch
Authors: Sundaravadivelu K. , Ng H. W. , Chai J. C. , Yu S. C. M. , Lam Y. C.
Published: December 2008

A mathematical modeling of argon thermal plasma flows inside a rod type cathode (RTC) plasma torch based on electromagnetic principle is presented. Numerical investigations on the model are carried out for a better understanding of its output characteristics in terms of the plasma velocity, temperature, mass fraction and electro-magnetic field calculations. A direct comparison of the present numerical results with a reported experimental data is made and found to be in fair agreement.
Transient Thermal Modeling of Pulsed Laser Irradiation of a Low Absorbing Multilayer Device Using a 2D Model
Authors: Shao D. , Mahajan R. L.
Published: December 2008

In this paper, we report the heat generation and temperature field in a multilayer device consisting of thin and weakly absorbing materials subject to pico-second to nano-second pulsed-laser heating. The interference effects due to the internal reflection and refraction are considered. A tracking method based on electromagnetic optics and wave optics is used to determine the two-dimensional electrical and magnetic fields. These fields are then used to calculate the heat generation and the accompanying temperature distribution. For demonstration, we apply this method to determine the temperature field in a ZnSe interference filter subject to inclined laser incidence on its side. The simulation results show strong localized heating in a narrow region along the side where laser power is incident. The localized heating produces several high power spots, aligned obliquely to the side surface. The results show that the pure absorption model is not valid for even small incident angles. Surface absorption may be a valid approximation but the heat flux distribution is not uniform.
Analytical and Experimental Analysis of Temperature Distribution in Synchronous Generators
Authors: Shin Sang-Baek , Song Yoo-Seok , Lee Dong-Jo , Seol Sin-Su , Lazar Gaspar
Published: December 2008

The present study investigates temperature distribution and heat transfer characteristics of synchronous generators to attain more efficient design and better cooling performance by using thermal network analysis and CFD. Under all circumstances, the temperature of rotor and stator windings must be kept below the maximum permissible temperature of insulations to maintain reliability and prolong durability of a machine. In this paper, the temperature rise of rotor winding, stator winding, and associated end-winding was calculated for some generators in a range of machine sizes. The temperature rise of the coolant at discrete points in its flow path was also predicted. Finally, the calculation results were compared with real test results. From the comparison, it was found that there was a good agreement between the analytical calculations and the experimental results.
Simultaneous Modeling of Heat and Mass Transfer of Steam-Air Mixture on a Shell and Tube Condenser Based on Film Theory
Authors: Haseli Yousef , Roudaki Javad M. R.
Published: December 2008

The idea of this work is to analyze condensation of steam-air mixture in a baffled shell and tube condenser with one path tube. Film Theory was used to consider the effects of heat and mass transfer on each other. Accordingly heat and mass transfer equations through proposed algorithm were solved simultaneously for each of baffle spacing considered as a control volume in this work. The predicted outlet temperature of both gas (air-water vapor mixture) and cooling media and total condensation rate is compared with the available experimental data taken from a typical semi-industrial condenser. A very good consistency of the analytical approach with the experimental data is achieved and presented.
Numerical Simulation of the Molten Carbonate Fuel Cell Performance Under Different Operational Conditions
Authors: Ma Zhiwen , Jeter S. M. , Abdel-Khalik S. I.
Published: December 2008

Thermal management of high temperature fuel cells is critical to fuel cell operation and reliability. Locally extreme cell temperature may cause high thermal stress and accelerated corrosion process, which could shorten the cell life and induce local electric and thermal contact loss. Fuel cell temperature usually is controlled by the gas flow stream cooling, or the internal reforming if the internal reforming process is incorporated inside the high temperature fuel cells. This paper discusses the gas flow rate effect on a single cell performance based on mathematical model. The parameter distribution and cell performance versus the gas flow rate are presented.
Thermal Performance of Heat Pipe Drill: Experimental Study
Authors: Jen Tien-Chien , Chen Yau-Min , Gutierrez Guatavo
Published: December 2008

An experimental study is performed in this paper to verify the concept of thermal management of using a heat pipe in the drilling process. The basic idea is to insert a heat pipe at the center of the drill tool with the evaporator located close to the drill tip, and condenser located at the end of the drill. In this way, heat accumulated in the drill tip can be transported to the remote section of the drill and remove it there to the tool holder, which attaches the drill. Temperatures at the drill tip as well as tool wear can be reduced significantly. In this paper, experimental investigations on a heat pipe drill for various heat flux inputs, inclination angles and rotating speeds are presented. The effect of contact resistance and tool holder (acting as heat sink) on heat pipe performance will also be demonstrated. The results presented in this paper may be used for important design and practical implementation considerations.
A Porous Media Reciprocal Flow Burner With Embedded Heat Exchangers
Authors: Contarin Fabiano , Barcellos William M. , Saveliev Alexei V. , Kennedy Lawrence A.
Published: December 2008

Superadiabatic combustion in porous media allows a stable burning of ultra-lean methane/air mixtures, far below flammability limits. The heat regeneration effect of the porous matrix and the low degree of thermal non-equilibrium between the gas and the solid phases keep temperature values above the minimum necessary for combustion and hence the CO and NOx production at extremely low levels. Due to the transient nature of this phenomenon, a method to confine the combustion into a practical burner has been engineered. The Reciprocal Flow Burner (RFB) is an effective and simple system to achieve this result. A heat exchanger embedded into the pellets makes it an appealing alternative for high-efficiency low-emission heat production. In the present work, a numerical model is compared to experiments to provide a better understanding of heat extraction from a RFB.
Symmetric Sink Flow and Heat Transfer Between Two Parallel Disks
Authors: dos Santos Bernardes Marco Aure´lio
Published: December 2008

The k-ε model are performed to investigate numerically the steady, turbulent, incompressible flow and heat transfer converging radially between two stationary disks, which is as a continuously developing flow problem under the internal boundary layer approximations. The effect of relaminarization was considered. This present study has presented a good agreement with the laminar investigation of Murphy et al [1], where no heat transfer was considered. At large values of the dimensionless radii (>> 1) the velocity profile becomes parabolic and invariant and the friction factor approaches the classic value obtained for fully developed flow between infinite plates, 24/Re0, where Re0 is an overall Reynolds number based on the volumetric flow rate and the disk spacing and is independent of radius. At radii less than one a typical external boundary layer evolves close to the wall with an approximately uniform core region, the boundary layer thickness decreases from one-half the disk spacing to values proportional to the local radii as the flow accelerates and the friction factor approaches the constant 2.17/Re0. A local Nusselt number, Nu = 230(r/R)0.650(1 − r/R)−0.386, where r is radial coordinate and R the radius of the disk, was estimated. A large overall Reynolds number was imposed and a relaminarization of the flow was observed. It was suggested that these results can be applicable for laminar and turbulent flow under Re0 = 106.