bluuebunny/crossref_metadata_2025_split huggingface dataset:
Diabetes Mellitus in Children and Adolescents
Authors: Weinzimer Stuart A. , Tamborlane William V. 
Published: April 2004

AbstractThe diagnosis and treatment of diabetes mellitus in children and adolescents present unique challenges to the clinician. Whereas once all children with diabetes were assumed to have type 1 diabetes, the increasing prevalence of type 2 diabetes in the pediatric population complicates both diagnostic and treatment algorithms. The goal of achieving near‐normal glucose control in youth demands an approach to treatment that attends to the developmental level of the child and the abilities and resources of the family. New developments in insulin delivery and glucose sensing technologies may improve quality of life and hold the promise of an eventual “artificial pancreas.” This chapter focuses on the specific clinical presentations and differential diagnoses of diabetes mellitus in children, as well as on current approaches to optimal in‐ and outpatient management of the disease and the incorporation of newer technologies into routine clinical practice.
Prevention of Type 2 Diabetes Mellitus
Authors: Simpson Richard W. , Tuomilehto Jaakko , Lindstrom Jaana , Shaw Jonathan E. , Zimmet Paul Z. 
Published: April 2004

AbstractAs the global epidemic of type 2 diabetes continues unabated with the associated increasing socioeconomic burden, attention is increasingly turning to the important issue of prevention. Type 2 diabetes is one part of the broader medical paradigm associated with cardiovascular disease—the metabolic syndrome. Population‐directed prevention is aimed at reducing the risk factor burden in both the general population and susceptible communities or ethnic groups. To date, there has been limited attention paid to dealing with the foreseen epidemic of type 2 diabetes. Targeted prevention involves higher intensity intervention strategies aimed at subjects with impaired glucose tolerance and impaired fasting glucose (prediabetes). There are now four major studies investigating lifestyle intervention in subjects with impaired glucose tolerance and all have shown significant reduction in progression to type 2 diabetes. Over the last 20 years there have been a number of targeted pharmacological intervention studies in subjects reported, with mixed results. Recently troglitazone, acarbose, and metformin have been shown to reduce progression to diabetes. There are now large targeted studies underway, examining the possible prevention of diabetes with ramipril, rosiglitazone, nateglinide, valsartan, and insulin. Whether lifestyle strategies or pharmacological intervention will also reduce cardiovascular outcomes is unknown. Possible but speculative mechanisms for diabetes prevention with pharmacological interventions are discussed. Many other issues remain to be addressed and these are the following: (1) How best to implement risk factor reduction (behavioral modification) in the population at large, in susceptible communities and ethnic groups? (2) How to achieve and maintain lifestyle changes targeted at prediabetic subjects? (3) What is the long‐term value and safety of pharmacological treatment of otherwise asymptomatic prediabetic subjects? (4) Are there benefits of combination therapies with lifestyle and pharmacological interventions in prediabetic individuals? (5) What are the socioeconomic costs and benefits, including cardiovascular protection, of implementing diabetes prevention programs?
Effect of filament drawdown on aerodynamic drag and heat transfer in fiber spinning
Authors: Miller C. 
Published: April 2004

AbstractThe momentum and thermal boundary layer equations are solved numerically to assess the effects of filament drawdown on aerodynamic drag and heat transfer in melt fiber spinning. It is found that, relative to the case without drawdown (constant filament velocity and diameter), the aerodynamic drag on the filament increases substantially, but the heat transfer rate is suppressed. Moreover, the air velocity profile eventually becomes fully developed (unlike the zero drawdown case), and the (velocity) boundary layer thickness, rather than continuing to grow with distance beneath the spinneret, eventually becomes proportional to the filament diameter, and thus decreases with increasing axial distance. Quantitative results are presented for the dimensionless drag force per unit length along the filament (the Drag number) and the Nusselt number as functions of the dimensionless axial distance and a new dimensionless parameter, the Drawdown Reynolds number. © 2004 American Institute of Chemical Engineers AIChE J, 50: 898–905, 2004
CFD study of fluid flow and wall heat transfer in a fixed bed of spheres
Authors: Nijemeisland Michiel , Dixon Anthony G. 
Published: April 2004

AbstractA study is presented of the relationship between the local flow field and the local wall heat flux in a packed bed of spheres. Computational fluid dynamics is used as a tool for obtaining the detailed velocity and temperature fields, for gas flowing through a periodic wall segment test cell. Results from the wall segment are demonstrated to reproduce those obtained from a full bed of spheres with tube‐to‐particle diameter ratio of N = 4. Attempts to correlate the local wall heat flux with local properties of the flow field, such as velocity components, velocity gradients, and components of vorticity, led to the conclusion that local heat transfer rates do not correlate statistically with the local flow field. Instead, a conceptual analysis was used to suggest that local patterns of wall heat flux are related to larger‐scale flow structures in the bed. © 2004 American Institute of Chemical Engineers AIChE J, 50: 906–921, 2004
Factors affecting solids segregation in circulating fluidized‐bed riser
Authors: Hirschberg B. , Werther J. 
Published: April 2004

AbstractAxial and radial segregation effects due to differences in particle sizes and solids densities were studied in a 0.2‐m‐dia. riser at gas velocities between 3.5 and 7 m/s and solids circulation rates between 8 and 40 kg/(m2·s). Two bed materials (a quartz sand/iron powder mixture and a quartz sand with a broad size distribution) with identical terminal velocity distributions were used. Local mean particle sizes and local mass fractions of the iron powder (for the mixture) decreased with height. Measurements of the solids streams revealed that the downflowing solids consist preferentially of large and/or heavy particles, while the reverse happens in the upward solids flow. The single particle terminal velocity is the decisive parameter affecting solids segregation. The comparison of both bed materials indicates that two bed materials will exhibit the same segregation patterns only if the distributions of the particles' terminal velocities in both materials are the same.
Transport processes of water and protons through micropores
Authors: Din Xue‐Dong , Michaelides Efstathios E. 
Published: April 2004

AbstractMolecular dynamics simulations were performed to study the movement of water molecules and protons in two pores: a small pore of radius 9.36 Å and a larger one of radius 12.24 Å. Inside the ionic solution, the wall charge densities are approximately −0.1 C/m2 and −0.2 C/m2. Water and proton distributions in the pore are affected strongly by the water content and the wall charge density. In the case of low wall charge density, if there is a sufficient number of water molecules in the pore, the protons are strongly hydrated to the water molecules and do not directly contact the wall. In the case of high wall charge density, most of the protons are attracted to the wall. Then, the wall charge and the absorbed protons together behave like a weakly charged wall. We found that the Poisson–Boltzmann theory fails to predict the proton distribution in these pores. The calculated electroosmotic drag coefficient, proton diffusion coefficient, and pore conductance are compared with the simulation results for the Nafion‐117 membrane. This study suggests that if the Nafion‐117 membrane is modeled as a large number of identical cylindrical pores, the effective wall charge densities in the pores will never reach the value of −0.2 C/m2.
Fractionation of BSA and lysozyme using ultrafiltration: Effect of gas sparging
Authors: Ghosh Raja , Li Qiangyi , Cui Zhanfeng 
Published: April 2004

AbstractFractionation of proteins by ultrafiltration is an interesting challenge. With a particular membrane, the protein – protein and protein – membrane interactions largely decide which protein passes through and which is retained. System hydrodynamics also affects protein fractionation as the transmission behavior of a protein is altered by concentration polarization. Therefore, disruption of the concentration polarization layer would help to maintain the native selectivity of the membrane and hence aid in protein fractionation. An attempt is made to use gas sparging, a technique proven effective in controlling concentration polarization to enhance the selectivity of separation of BSA (MW 67,000) and lysozyme (MW 14,100). The effects of gas flow rate, liquid flow rate and feed concentration on the selectivity of fractionation are examined. Gas sparging enhances protein fractionation; under suitable solution conditions, nearly complete separation of BSA and lysozyme was achieved with gas sparged ultrafiltration. The permeate flux was also increased by gas sparing. The mechanism of enhancement is explained in terms of disruption of the concentration polarization layer and enhanced mass transfer due to bubble‐induced secondary flow.
Dual diffusion and finite mass exchange model for adsorption kinetics in activated carbon
Authors: Do D. D. , Wang K. 
Published: April 2004

AbstractA model allowing for the finite mass exchange between the two phases is proposed for the description of adsorption kinetics in activated carbon. This model based on Do's earlier structural model for activated carbon involves three mass‐transfer processes: pore diffusion, adsorbed phase diffusion, and finite mass interchange between the fluid and adsorbed phases. The solid phase is heterogeneous, which is characterized by the micropore size distribution. The interaction between the adsorbate molecule and the micropore is calculated from the Lennard‐Jones potential theory. The model developed for nonpolar adsorbates is tested with the experimental data of seven adsorbates (paraffin gases, aromatics, carbon dioxide, and sulfur dioxide) on pellets of different shapes and sizes and at various operating conditions. The finite kinetics play an important role in the overall kinetics. Failure to account for this finite kinetics makes the model unable to describe correctly the desorption behavior, since under such conditions, the ability of the particle to release adsorbed molecules is dictated mostly by the resistance at the pore mouth of the micropore.
A break‐even analysis of distillation–membrane hybrids
Authors: Pressly Thomas G. , Ng Ka M. 
Published: April 2004

AbstractThe use of distillation–membrane hybrids is examined for the separation of two component mixtures exhibiting a tangent pinch, azeotrope, or low relative volatility. The merits of various process alternatives are discussed. A procedure for screening calculations is presented that allows the determination of the break‐even cost for a membrane, above which the hybrid would be too costly to be competitive. This approach is applicable to the screening of all the types of membranes and can be used to target the desirable membrane properties. Screening calculations are performed for water–acetic acid, ethanol–water, and propylene–propane systems to demonstrate the inherent trade‐offs of the hybrids and the effect of phase behavior on the performance.
FIR model identification: Parsimony through kernel compression with wavelets
Authors: Nikolaou Michael , Vuthandam Premkiran 
Published: April 2004

AbstractAlthough finite impulse response (FIR) models are nonparsimonious, they are frequently used in model predictive control systems because they can fit arbitrarily complex stable linear dynamics. However, identification of FIR models from experimental data may result in data overfitting and high modeling uncertainty. To overcome this, FIR models may be determined by regularization‐based least squares and indirectly after prior identification of other parametric models such as ARX. In both cases, some prior knowledge about the model is essentially assumed to be known. ARX models, although parsimonious in terms of the number of identified parameters, perform poorly for bad choices of model structure and order. A methodology for the direct identification of parsimonious FIR models is proposed. In this way, most advantages of the FIR structure are retained without its disadvantages. The idea relies on the effective use of some prior information about the model through wavelet‐based signal compression. The proposed methodology is compared with other FIR identification methodologies, on the basis of the closeness of the identified FIR to the true FIR, steady‐state gain estimation, and analysis of the prediction residuals on a cross‐validation set of fresh data. Simulation studies on a single‐input‐single‐output process show that this method performs very well in all tests considered. Certain industrial practices are shown to be special cases of the proposed formalism.
Determining the model order of nonlinear input/output systems
Authors: Rhodes Carl , Morari Manfred 
Published: April 2004

AbstractA method for determining the proper regression vector for recreating the dynamics of nonlinear systems is presented. The false nearest neighbors (FNN) algorithm, originally developed to study chaotic time series, is used to determine the proper regression vector for input/output system identification and inferential prediction using only time‐series data. The FNN algorithm for solving these problems is presented, and the problem of analyzing noise corrupted time series is discussed. The application of the algorithm to a number of examples including an electrical‐leg stimulation experiment, an industrial pulp‐digester model, a polymerization model, and a distillation‐column simulation is presented and the results are analyzed.
Automatic synthesis of thermodynamically feasible reaction clusters
Authors: Holiastos Konstantinos , Manousiouthakis Vasilios 
Published: April 2004

AbstractReaction clusters serve to carry out reactions whose thermodynamic yield is too low for practical large‐scale application. They therefore play an important role in the economics of the process and can decisively control its environmental impact. Reaction cluster synthesis must address such economic and environmental considerations. This was successfilly accomplished in this work, which is the first employing an optimization technique for this task. The problem formulation ensures that all mass balances are satisfied, that all reactions are thermodynamically feasible, and that they follow certain user‐defined characteristics of a generalized chemical reaction. In addition, given a set of chemical species, all clusters are identified that can represent this reaction; the ones found first are the most promising candidates. The formulation is flexible, accommodating a different number of reactions per cluster and allowing specification of many attributes by the user.
Novel concept prototype of low‐power‐consumption electrically heatable catalyst
Authors: Nakouzi Sabine R. , Narula Chaitanya K. , McBride James R. , Nietering Kenneth E. , Visser Jacobus H. , Adamczyk Andrew A. 
Published: April 2004

AbstractElectrically heated catalyst devices (EHCs) are important for treating exhaust gases in the 20 to 120 s warmup period after a cold start when about 70% of the total hydrocarbon (HC) and carbon monoxide (CO) emissions from a modern gasoline powered vehicle are released. Although known for several years, EHCs have not been deployed because these devices are cost‐ and energy‐intensive. An alternate EHC prototype proposed here is based on our reasoning that only the platinum group metals and the molecules undergoing oxidation need to be at light‐off temperatures and it is not necessary to waste energy to heat the whole catalyst. The concept prototype, fabricated on a glass coupon, resistively heats the fluorine doped tin oxide film beneath the washcoat to bring a palladium‐titania washcoat to the CO and HC light‐off temperatures. The electrically powered concept prototype showed light‐off temperatures of 250°C and 260°C for CO and HC, respectively, in laboratory tests with simulated exhaust gases at 25°C. A device based on this concept is estimated to attain the 1‐kW target power consumption required for the deployment of the EHC.
Role of transition metal oxides in metal dusting: Density functional study
Authors: Cheng Hansong , Reiser David B. , Mathias Paul M. , Dean Sheldon 
Published: April 2004

AbstractDensity function theory was applied to study the mechanisms and energetics of two major metal dusting processes represented by Boudouard and steam‐carbon reactions on the FeO(100) surface. Cluster models were utilized to represent the surface. The chosen cluster model was validated by examining CO adsorption binding energies on clusters of various sizes. We show that the lattice relaxation has a relatively small effect on the adsorption. The reaction process involving direct abstraction of O from the surface by CO was excluded from consideration of the overall dusting processes due to unfavorable energetics. Minimum energy path calculations were carried out to investigate the reaction mechanisms. It was found that both the Boudouard and steam‐carbon reactions are thermochemically and kinetically unfavorable on transition metal oxide surfaces. Detailed insight into the reaction mechanisms was obtained by following the reaction trajectories and analyzing the electron population distribution along the reaction paths. This study elucidates the empirical observation that metal oxide can often minimize metal dusting.
Preparation of spherical oxalate particles of rare earths in emulsion liquid membrane system
Authors: Hirai Takayuki , Okamoto Norihiko , Komasawa Isao 
Published: April 2004

AbstractSubmicron‐sized spherical oxalate particles of rare earths were prepared by using an emulsion liquid membrane (ELM, water‐in‐oil‐in‐water (W/O/W) emulsion) system, consisting of Span 83 (sorbitan sesquioleate) as a surfactant and EHPNA (2‐ethylhexylphosphonic acid mono‐2‐ethylhexyl ester) as an extractant (cation carrier). Rare‐earth ions were extracted from the external water phase and stripped into the internal water phase to make submicron‐sized oxalate particles. In the case of Ce, Pr, Nd, Sm, and Gd, well‐defined spherical oxalate particles (0.2 – 0.6 μm dia.) were obtained, following the formation of primary particles of about 20 nm. In contrast, less spherical or rather tabular particles were formed for La, Dy, and Y, possibly owing to their formation in the external phase following some breaking of the water‐in‐oil (W/O) emulsion drop. Oxalate particles of Yb were not obtained in this system. Effects of the internal water droplet size, the rare‐earth ion concentration in the external water phase, and the volume ratio of organic membrane phase to internal water phase of the W/O emulsion (O/A ratio), on the size of spherical particles, were investigated. A simulation study based on the model of transport mechanism of rare‐earth ions through the organic membrane phase revealed that the particle size was determined by the distribution of rare‐earth ions into the internal water droplets, as confirmed by the experimental results. The control of the particle size was found to be feasible by control of the feed rare‐earth concentration and size of the internal water droplets.
Hydrogen‐bond cooperativity in 1‐alkanol + n‐alkane binary mixtures
Authors: Gupta Ram B. , Brinkley Ray L. 
Published: April 2004

AbstractHydrogen‐bond cooperativity is an effect when hydrogen bonding is influenced by the previously formed hydrogen bond on the molecules. Using Fourier‐transform infrared spectroscopy, we have measured the extent of self hydrogen bonding in 1‐hexanol and 1‐pentanol dissolved in n‐hexane. Conventional theories without hydrogen‐bond cooperativity, such as the statistical‐association‐fluid theory, lattice‐fluid‐hydrogen‐bonding theory, and associated perturbed‐anisotropic‐chain theory, cannot represent the experimental data accurately. The extended lattice‐fluid‐hydrogen‐bonding theory that includes hydrogen‐bond cooperativity agrees well with the experimental data. Study suggests that the equilibrium constant for the second hydrogen bond on 1‐alkanol molecules is 10 times larger than that for the first hydrogen bond formation. Hence, strong hydrogen bond cooperativity exists in 1‐alkanol self association. Equations of state dealing with 1‐alkanol mixtures need to be modified to account for this strong hydrogen‐bond cooperativity.
Kinetics of protein deposition and replacement from a shear flow
Authors: Mandrusov E. , Yang J. D. , Pfeiffer N. , Vroman L. , Puszkin E. , Leonard E. F. 
Published: April 2004

AbstractKinetics of plasma protein deposition and replacement from a shear flow of full strength and diluted blood plasma onto prewetted glass were studied both numerically and experimentally. A band of fibrinogen moving down the adsorbing surface was predicted and observed. The band was shown to define the region where blood platelets subsequently adhered to the surface. Since platelet adhesion is a fundamental component of thrombosis, this observation is potentially pertinent to the long‐sought mechanism that determines where thrombus forms during shear flow of blood through artificial devices. The discrepancies between the mathematical model and experimental observations are explained by the presence of the natural convection, arising from density differences between plasma and the wetting fluids.
Blowdown of pipelines carrying flashing liquids
Authors: Fairuzov Yuri V. 
Published: April 2004

AbstractA mathematical model is developed to simulate a blowdown of a long pipeline conveying a flashing multicomponent mixture. The effect of the thermal capacitance of the pipe was incorporated into the model by employing a novel approach in the formulation of the energy equation for the fluid flow in the pipeline. The model was validated by comparison with previously published experimental data for the blowdown of a pipe containing a two‐component mixture. A detailed study was performed to investigate the effect of heat transfer between the fluid flow and the pipe wall on the process of depressurization of a long pipeline. Numerical simulations were carried out to assess the effect of friction on the blowdown time. The results obtained lead to a better understanding of the blowdown phenomenon and can be used for predicting the consequences of controlled or uncontrolled releases of flashing liquids from long pipelines.
Flow and axial dispersion simulation for traveling axisymmetric Taylor vortices
Authors: Howes Tony , Rudman Murray 
Published: April 2004

AbstractNumerical experiments using a finite difference method were carried out to determine the motion of axisymmetric Taylor vortices for narrow‐gap Taylor vortex flow. When a pressure gradient is imposed on the flow the vortices are observed to move with an axial speed of 1.16 ± 0.005 times the mean axial flow velocity.The method of Brenner was used to calculate the long‐time axial spread of material in the flow. For flows where there is no pressure gradient, the axial dispersion scales with the square root of the molecular diffusion, in agreement with the results of Rosenbluth et al. for high Peclet number dispersion in spatially periodic flows with a roll structure. When a pressure gradient is imposed, the dispersion increases by an amount approximately equal to 6.5 × 10−4 W2d2/Dm, where W is the average axial velocity in the annulus, analogous to Taylor dispersion for laminar flow in an empty tube.