bluuebunny/crossref_metadata_2025 huggingface dataset:
Chief Executive Officer Equity Incentives and Accounting Irregularities
Authors: ARMSTRONG CHRISTOPHER S. , JAGOLINZER ALAN D. , LARCKER DAVID F.
Published: October 2009

This study examines whether Chief Executive Officer (CEO) equity‐based holdings and compensation provide incentives to manipulate accounting reports. While several prior studies have examined this important question, the empirical evidence is mixed and the existence of a link between CEO equity incentives and accounting irregularities remains an open question. Because inferences from prior studies may be confounded by assumptions inherent in research design choices, we use propensity‐score matching and assess hidden (omitted variable) bias within a broader sample. In contrast to most prior research, we do not find evidence of a positive association between CEO equity incentives and accounting irregularities after matching CEOs on the observable characteristics of their contracting environments. Instead, we find some evidence that accounting irregularities occur less frequently at firms where CEOs have relatively higher levels of equity incentives.
Capillary Endothelial Na+, K+, ATPase Transporter Homeostasis and a New Theory for Migraine Pathophysiology
Authors: Harrington Michael G. , Fonteh Alfred N. , Arakaki Xianghong , Cowan Robert P. , Ecke Laurel E. , Foster Hailey , Hühmer Andreas F. , Biringer Roger G.
Published: October 2009

(Headache2010;50:459‐478)

Background.—Cerebrospinal fluid sodium concentration ([Na+]csf) increases during migraine, but the cause of the increase is not known.

Objective.—Analyze biochemical pathways that influence [Na+]csfto identify mechanisms that are consistent with migraine.

Method.—We reviewed sodium physiology and biochemistry publications for links to migraine and pain.

Results.—Increased capillary endothelial cell (CEC) Na+, K+, ‐ATPase transporter (NKAT) activity is probably the primary cause of increased [Na+]csf. Physiological fluctuations of all NKAT regulators in blood, many known to be involved in migraine, are monitored by receptors on the luminal wall of brain CECs; signals are then transduced to their abluminal NKATs that alter brain extracellular sodium ([Na+]e) and potassium ([K+]e).

Conclusions.—We propose a theoretical mechanism for aura and migraine when NKAT activity shifts outside normal limits: (1) CEC NKAT activity below a lower limit increases [K+]e, facilitates cortical spreading depression, and causes aura; (2) CEC NKAT activity above an upper limit elevates [Na+]e, increases neuronal excitability, and causes migraine; (3) migraine‐without‐aura may arise from CEC NKAT over‐activity without requiring a prior decrease in activity and its consequent spreading depression; (4) migraine triggers disturb, and treatments improve, CEC NKAT homeostasis; (5) CEC NKAT‐induced regulation of neural and vasomotor excitability coordinates vascular and neuronal activities, and includes occasional pathology from CEC NKAT‐induced apoptosis or cerebral infarction.
Migraine and Obesity: Epidemiology, Mechanisms, and Implications
Authors: Peterlin B. Lee , Rapoport Alan M. , Kurth Tobias
Published: October 2009

(Headache 2010;50:631‐648)

Adipose tissue is a dynamic neuroendocrine organ that is involved in multiple physiological and pathological processes, and when excessive, results in obesity. Clinical and population‐based data suggest that migraine and chronic daily headache are associated with obesity, as estimated by anthropometric indices. In addition, translational and basic science research shows multiple areas of overlap between migraine pathophysiology and the central and peripheral pathways regulating feeding. Specifically, neurotransmittors such as serotonin, peptides such as orexin, and adipocytokines such as adiponectin and leptin have been suggested to have roles in both feeding and migraine. In this article, we first review the definition and ascertainment of obesity. This is followed by a review of the clinical and population‐based studies evaluating the associations between obesity and chronic daily headache and migraine. We then discuss the central and peripheral pathways involved in the regulation of feeding, where it overlaps with migraine pathophysiology, and where future research may be headed in light of these data.
Probing tumor and peritumoral tissues in superficial and nodular basal cell carcinoma using polarized Raman microspectroscopy
Authors: Ly Elodie , Durlach Anne , Antonicelli Frank , Bernard Philippe , Manfait Michel , Piot Olivier
Published: October 2009

Abstract:  Basal cell carcinoma (BCC) can sometimes lead, through a possible invasion of the dermis and the subcutaneous tissue, to serious local damage to the patient. Several histological types of BCC are reported, among them, the superficial, nodular and infiltrative forms. This study reports the use of polarized Raman microspectroscopy on the nodular and superficial types to discriminate between healthy epidermis and tumor, and between normal and peritumoral stroma. This technique probes additional information than conventional Raman spectroscopy because it is sensitive to the molecular ordering of tissue components. Depolarization ratios and hierarchical cluster analysis demonstrate that polarized Raman microspectroscopy can better identify the tumor and the peritumoral dermis than conventional Raman microspectroscopy, and hence gives potential complementary data about their molecular characteristics (molecular composition, secondary structure of proteins, intra‐ and/or inter‐molecular bonding). Our findings also show that although superficial and nodular types of BCC were analysed, clear differences between the spectra of peritumoral and normal dermis could be detected.
Absence of modulation of CD4+CD25high regulatory T cells in CTCL patients treated with bexarotene
Authors: Knol Anne Chantal , Quéreux Gaëlle , Brocard Anabelle , Ballanger Fabienne , Khammari Amir , Nguyen Jean‐Michel , Dréno Brigitte
Published: October 2009

Please cite this paper as: Absence of modulation of CD4+CD25high regulatory T cells in CTCL patients treated with bexarotene. Experimental Dermatology 2010; 19: e95–e102.

Abstract:  Cutaneous T‐cell lymphoma (CTCL) are a heterogeneous group of lymphoproliferative disorders, characterized by the infiltration of the epidermis by mature and activated malignant CD4+ T‐lymphocytes. Retinoids such as retinoic acid and synthetic analogues have long been used alone or in combination with other therapies for CTCL. Bexarotene, the first synthetic highly selective RXR retinoid, was approved for the treatment of all stages of CTCL in patients refractory to at least one systemic therapy. Recently, six cases in which the initiation of bexarotene therapy for CTCL was associated with the progression of internal disease despite improvement of cutaneous signs and symptoms were reported. Moreover, it has been established that retinoids promote the generation of CD4+ Foxp3+ regulatory T cells, raising the question of an induction of regulatory T‐cells by bexarotene. The aim of this work was to determine if bexarotene induces an increase of functional regulatory T cells which could play a role in the development of secondary extra‐cutaneous lymphomas. Regulatory T cells were studied both in cutaneous biopsy specimens using an immunohistochemical analysis of CD4, CD25 and Foxp3 and in blood where proportion and functionality of circulating CD4+CD25high T‐cells were determined. The study was performed in 10 patients [five patients with Sézary syndrome (SS) and five mycosis fungoïdes (MF)], treated for 6 months with bexarotene. Four healthy donors were used as controls for phenotypic and functional analysis on PBL. We found that the frequency of CD4+CD25high Treg cells was not significantly different before starting bexarotene and after 6 months of treatment in CTCL patients. However, we observed that the frequency of CD4+CD25high Treg cells before the beginning of the treatment was significantly increased compared to healthy donors. In addition, functional assays demonstrated that Foxp3 expressing CD4+CD25high T‐cells were capable of suppressing autologous CD4 + CD25− T‐cell proliferation. In the present work, we detected the presence of functional circulating CD4+CD25high Foxp3+ regulatory T‐cells in CTCL patients, with an increased frequency compared to healthy donors. The treatment with bexarotene does not seem to affect the regulatory T‐cell compartment.
Lipidome of narrow‐band ultraviolet B irradiated keratinocytes shows apoptotic hallmarks
Authors: Reich Adam , Schwudke Dominik , Meurer Michael , Lehmann Bodo , Shevchenko Andrej
Published: October 2009

Please cite this paper as: Lipidome of narrow‐band ultraviolet B irradiated keratinocytes shows apoptotic hallmarks. Experimental Dermatology 2010; 19: e103–e110.

Background:  UV light triggers a variety of biological responses in irradiated keratinocytes that might be associated with global perturbation of their lipidome. However, lipids that are specifically affected and the exact molecular mechanisms involved remain poorly understood.

Objectives:  To characterize time‐dependent changes of the lipidome of cultured keratinocytes induced by narrow‐band ultraviolet B (NB‐UVB) irradiation.

Methods:  Immortalized human keratinocytes (HaCaT) were cultured under standard conditions, irradiated with NB‐UVB light (311 nm) at 400 and 800 mJ/cm2 and collected 1, 2, 3, 6, 12 and 24 h later for lipid extraction. Lipid extracts were separated on silica plates in chloroform/ethanol/water/triethylamine (35:40:9:35) and in n‐hexane/ethylacetate (5:1) followed by quantitative shotgun lipidomics analysis.

Results:  Irradiation with 800 mJ/cm2 of NB‐UVB altered morphology and lipidome composition of HaCaT cells. Ceramide content increased two‐fold 6‐ and 12‐h postirradiation with 800 mJ/cm2, followed by threefold increase in triacylglycerols (TAGs) that peaked at 24 h. In addition, we observed marked increase of various phosphatidylcholine and phosphatidylethanolamine ethers, whereas phosphatidylcholine‐species with short‐chain fatty acid moieties decreased. The abundance of other lipid species was altered to lesser extent or remained unchanged.

Conclusions:  NB‐UVB affected the cellular lipidome of keratinocytes in strictly apoptosis‐specific manner.
Fluorescence induction of protoporphyrin IX by a new 5‐aminolevulinic acid nanoemulsion used for photodynamic therapy in a full‐thickness ex vivo skin model
Authors: Maisch Tim , Santarelli Francesco , Schreml Stephan , Babilas Philipp , Szeimies Rolf‐Markus
Published: October 2009

Please cite this paper as: Fluorescence induction of protoporphyrin IX by a new 5‐aminolevulinic acid nanoemulsion used for photodynamic therapy in a full‐thickness ex vivo skin model. Experimental Dermatology 2010; 19: e302–e305.

Abstract:  An ex vivo porcine skin model was utilized to analyse the penetration of 5‐aminolevulinic acid (5‐ALA) contained in a nanoemulsion‐based formulation BF‐200 ALA (10% 5‐ALA‐hydrochloride) versus 16% aminolevulinate methyl ester‐hydrochloride in a commercially cream (MAL cream) by fluorescence microscopy of their common metabolite protoporphyrin IX (PpIX) after 3, 5, 8 and 12 h. Fluorescence signals of PpIX in pig skin treated with BF‐200 ALA were stronger than those for MAL cream. At 8 and 12 h, the PpIX fluorescence signals were 4.8‐ and 5.0‐fold higher than those measured after MAL cream application. Fluorescence signals of PpIX after application of BF‐200 ALA were detected in deeper tissue layers of the epidermis than after application of MAL cream (97.2 ± 5.7 μm for BF‐200 ALA vs 42.0 ± 4.2 μm for MAL cream). These data implicate that BF‐200 ALA in photodynamic therapy might lead to a superior therapeutically effect of intraepidermal (in situ) squamous cell carcinomas.
Insulin‐like growth factor‐I E peptides: implications for ageing skeletal muscle
Authors: Velloso Cristina P. , Harridge Stephen D. R.
Published: October 2009

In skeletal muscle there is good evidence to suggest that locally produced insulin‐like growth factor‐1 (IGF‐I), rather than circulating IGF‐I, is important in regard to muscle mass maintenance, repair and hypertrophy. This “mature” IGF‐I comprises exons 3 and 4 of the IGF‐I gene, but during processing the full length gene (which contains six exons) is subject to a process of alternative splicing. As a result smaller peptides (E peptides) are believed to be cleaved from the mature IGF‐I peptide during processing of the prohormone and the likelihood is that they have different biological roles. In human skeletal muscle three transcripts encoding for these splice variants (IGF‐IEa, IGF‐IEb and IGF‐IEc, also known as MGF) can be identified. When studied at the mRNA level these three transcripts are known to be upregulated in the muscles of elderly people following high resistance exercise, albeit with different time courses. However, compared with mature IGF‐I relatively little is known about the mechanism of action of the different E peptides.
Skiing Less Often in a Warmer World: Attitudes of Tourists to Climate Change in an Australian Ski Resort
Authors: PICKERING CATHERINE MARINA , CASTLEY J. GUY , BURTT MICHELLE
Published: October 2009

Climate change will affect tourism destinations that are dependent on natural resources, such as snow. Currently there is limited research into attitudes, intentions and actual visitation patterns of skiers in response to reduced snow cover. Therefore the awareness of, and attitudes towards, climate change of 351 ski tourists were assessed in the largest ski resort in Australia in 2007, repeating a survey conducted in 1996. Ninety percent of skiers in 2007 would ski less often in Australian resorts if the next five years had low natural snow, up from 75% of skiers surveyed in 1996: 69% would ski less often, 5% would give up and 16% would ski at the same levels but overseas. Nearly all skiers thought that climate change would affect the ski industry (87% compared with 78% in 1996), and that this would occur sooner than in the 1996 survey. Visitation in a poor snow year (2006, +0.85°C average annual temperature, 54% less natural snow) was −13.6% of the long‐term average, indicating poor natural snow resulted in decreased visitation, despite extensive use of snow making. The implications of changes in climate conditions and tourist attitudes for Australian ski resorts are assessed including for snow making and summer tourism.
Controlling the Bleeding of Carmine Colorant in Crabstick
Authors: Poowakanjana Samanan , Park Jae W.
Published: October 2009

ABSTRACT:  Carmine used to color surimi seafood often seeps or bleeds from red‐colored meat to white meat when vacuum‐packed products go through high‐temperature long‐time pasteurization. Various physical and chemical treatments were examined to investigate means to inhibit or minimize carmine bleeding in surimi seafood products. Degree of bleeding was analyzed using L* (lightness) and a* (redness) as affected by carmine concentrations, pH, pasteurization conditions, and added calcium compounds. Bleeding was significantly affected by carmine concentrations. Optimum carmine concentration in color paste was 0.1%. Bleeding increased when pasteurization time and/or temperature increased. Color bleeding was also affected by moisture content of surimi paste. Carmine bleeding was minimized as pH of color solution decreased. The degree of bleeding was controlled as calcium compounds were added in color solution in a descending order of calcium chloride, calcium acetate, and calcium hydroxide. Minimal inhibition was obtained when color solutions contained calcium citrate, tricalcium phosphate, and calcium lactate.

Practical Application: This manuscript addresses one of the long time problems in the surimi crabstick industry. Various means to control carmine bleeding or color transfer under high temperature for long time pasteurization were demonstrated. However, further study must continue to stop bleeding completely.
Assessing morphological and DNA‐based diet analysis techniques in a generalist predator, the arrow squid Nototodarus gouldi
Authors: BRALEY MICHELLE , GOLDSWORTHY SIMON D. , PAGE BRAD , STEER MIKE , AUSTIN JEREMY J.
Published: October 2009

Establishing the diets of marine generalist consumers is difficult, with most studies limited to the use of morphological methods for prey identification. Such analyses rely on the preservation of diagnostic hard parts, which can limit taxonomic resolution and introduce biases. DNA‐based analyses provide a method to assess the diets of marine species, potentially overcoming many of the limitations introduced by other techniques. This study compared the effectiveness of morphological and DNA‐based analysis for determining the diet of a free‐ranging generalist predator, the arrow squid (Nototodarus gouldi). A combined approach was more effective than using either of the methods in isolation. Nineteen unique prey taxa were identified, of which six were found by both methods, 10 were only detected using DNA and three were only identified using morphological methods. Morphological techniques only found 50% of the total number of identifiable prey taxa, whereas DNA‐based techniques found 84%. This study highlights the benefits of using a combination of techniques to detect and identify prey of generalist marine consumers.
Intersession repeatability of optical coherence tomography measures of retinal thickness in early age‐related macular degeneration
Authors: Patel Praveen J. , Chen Fred K. , Ikeji Felicia , Tufail Adnan
Published: October 2009

Purpose:  To determine the intersession repeatability of Stratus optical coherence tomography (OCT) measures of retinal thickness in patients with age‐related macular degeneration (AMD).

Methods:  Measurement of retinal thickness was performed over four sessions over 12 weeks using a standardized OCT protocol with the fast macular thickness map in 67 non‐treated eyes of 67 patients with AMD enrolled in a clinical trial. The intrapatient standard deviation (Sw) and 95% coefficient of repeatability (CR) (), expressed in μm and as a percentage of mean retinal thickness, were calculated to estimate intersession repeatability.

Results:  The CR was 32 μm for the average retinal thickness in the central 1 mm A1 subfield [95% confidence interval (CI) 31–33 μm] and 53 μm (95% CI 51–55 μm) for the centre‐point thickness (CPT). When expressed as a percentage, the CR was 15% (95% CI 14–16) for the central 1 mm A1 subfield and 29% (95% CI 27–30) for the CPT measure.

Conclusion:  The average central 1 mm (A1) subfield retinal thickness measure shows good intersession repeatability in patients with stable, early AMD with poorer repeatability for the CPT measure. The results suggest that a change in Stratus OCT retinal thickness of more than 32 μm in the central A1 subfield is more indicative of true clinical change in these patients.
Effective Thermal Conductivity for Combined Radiation and Free Convection in an Optically Thick Heated Fluid Layer
Authors: Epstein M. , Cheung F. B. , Chawla T. C. , Hauser G. M.
Published: October 2009

The effective thermal conductivity for radiative heat transfer within an optically thick fluid layer undergoing high Rayleigh number convection is derived. This result is combined with available “pure” free-convection heat-transfer correlations to obtain closed-form analytical descriptions of the gross properties of a radiating fluid layer heated internally or from below. These simple solutions compare favorably with recent work in which the governing energy equation incorporating both turbulent heat transport and thermal radiation is solved numerically.
An Exact Solution of the Sublimation Problem in a Porous Medium
Authors: Lin Sui
Published: October 2009

Sublimation problem with coupled heat and mass transfer taking place in a porous halfspace is defined and exact solutions for temperature and moisture distributions as well as the position of the moving sublimation front are obtained. The condition for the limitation of the sublimation process is also determined.
Analytically Determined Fin-Tip Heat Transfer Coefficients
Authors: Sparrow E. M. , Hsu C. F.
Published: October 2009

An analysis was performed to determine the fin-tip heat transfer coefficients for an array of straight longitudinal fins attached to a plane wall. The array is shrouded by an adiabatic surface positioned adjacent to the tips, with a clearance gap between the shroud and the tips. The analysis was carried out for hydrodynamically and thermally developed conditions and for laminar flow. Results were obtained from numerical solutions of the momentum and energy conservation equations for the fluid and the energy equation for the fin, with two-dimensional conduction being permitted in the fin. From the solution, the average fin-tip heat transfer coefficient was evaluated and compared with the average coefficient for a segment of the principal face of the fin that is adjacent to the tip, the segment length being half the tip width. These coefficients were found not to differ too greatly, with the largest deviations being on the order of twenty-five percent. When connective heat transfer at the fin tip was suppressed, the heat transfer coefficients on the tip-adjacent portion of the principal face increased markedly. Because of this compensating effect, the overall performance of the fin is about the same when the tip is either convectively active or adiabatic. In general, large variations of the fin heat transfer coefficient were encountered between the base and the tip, with the smallest values at the base and the largest values at the tip.
Unsteady Heat Flow between Solids with Partially Contacting Interface
Authors: Sadhal S. S.
Published: October 2009

The problem of the transient thermal response of two semi-infinite solids not making perfect contact, is treated analytically by modeling the interface to be a series of equally spaced strips making perfect contact. The remaining area is assumed to perfectly insulated, and a criterion is established for the validity of this assumption, taking radiation into consideration. The mixed interface conditions present a considerable difficulty and a long-time perturbation scheme is therefore used to obtain approximate expressions for the transient temperature distributions, average heat flux and the thermal contact resistance. The method is applicable to a large class of problems with mixed boundary conditions for which the existing techniques give exact solutions only for the steady state.
Bubble Growth During Decompression of a Liquid
Authors: Cha Y. S. , Henry R. E.
Published: October 2009

The solution of the diffusion equation in spherical coordinates subject to time-dependent boundary conditions is derived. The solution can be employed to describe the growth of either a diffusion-controlled gas bubble or a heat transfer-controlled vapor bubble provided that convection effect is negligible. It is shown that the Epstein-Plesset solution for a gas bubble in a constant pressure field and the Jones-Zuber solution in a Cartesian coordinate system for a vapor bubble in a variable pressure field are special cases of the present solution. Numerical results obtained from the present analysis compare favorably with available experimental data for the growth of both gas and vapor bubbles during decompression processes.
Homogeneous Nucleation and the Spinodal Line
Authors: Lienhard J. H. , Karimi Amir
Published: October 2009

The limit of homogeneous nucleation in a liquid is shown to lie very close to its liquid spinodal line. It is also argued that the homogeneous nucleation prediction should be based on a comparison of the critical work of nucleation with the “potential well” energy instead of the kinetic molecular energy. The result is a new prediction of the liquid spinodal line for water that is valid to large negative pressures. This prediction compares well with spinodal points obtained by extrapolating liquid and vapor water data with the Himpan equation.
Semi-Transparent Gold Film as Simultaneous Surface Heater and Resistance Thermometer for Nucleate Boiling Studies
Authors: Oker E. , Merte H.
Published: October 2009

A large (22 × 25 mm) semi-transparent thin film of gold, approximately 400 Å in thickness, is deposited on a glass substrate for simultaneous use as a heat source and resistance thermometer. Construction techniques and calibration procedures are described, and a sample application to a transient boiling process is included with simultaneous high speed photographs taken through the thin film from beneath.
A Generalization of the System Mean Void Fraction Model for Transient Two-Phase Evaporating Flows
Authors: Beck B. T. , Wedekind G. L.
Published: October 2009

The system mean void fraction model has been successful in the prediction of a variety of transient evaporating and condensing flow phenomena; however, applications of the model have been restricted to physical situations involving complete vaporization or condensation. The major contribution of this paper is the development of a generalization of the existing system mean void fraction model, applicable to the broader class of transient two-phase flow problems involving incomplete vaporization. Present applications of the generalized system mean void fraction model to transient evaporating flows indicate good agreement with experimental void fraction and mass flux response data available in the literature. These data represent a variety of different flow geometries, types of fluids, and a wide range of operating conditions.
On the Transient Convective Transport from a Body of Arbitrary Shape
Authors: Morrison F. A. , Griffiths S. K.
Published: October 2009

The net rate of transient convective heat transfer from a body at uniform temperature in steady flow is shown to be invariant to pointwise reversal of the flow. Such reversal is physically possible in both creeping and potential flows. Creeping flow and the unseparated potential flow of a low Prandtl number fluid yield physically important transfer problems. Additionally, the theorem is applicable to problems for which flow reversal has no physical significance; numerical reversal of any incompressible streaming flow will leave the net transfer rate unchanged. The proof is not based on symmetry and places no restriction on the shape of the body. It remains valid over the entire range of Reynolds and Peclet numbers even though local transfer rates may differ significantly in the two directions of flow. The theorem applies to the analogous mass transport and is generalized to include a homogeneous first order reaction decreasing the concentration.
Heat Transfer and Friction Loss in Laminar Radial Flows through Rotating Annular Disks
Authors: Mochizuki S. , Yang Wen-Jei
Published: October 2009

Heat transfer and pressure drop performance are experimentally studied for laminar radial flow through a stack of corotating annular disks. The disk surfaces are heated by condensing steam to create constant surface temperature condition. The traditionally defined friction factor is modified to include the effect of centrifugal force induced by the rotation of the heat transfer surface on core pressure drop. Empirical equations are derived for the heat transfer and friction factors at zero rotational speed. Test results are obtained for various rotational speeds. It is disclosed that (1) The transition in the radial flow through rotating parallel disk passages occurs at the Reynolds number (based on the hydraulic diameter of the flow passage) of 3000 at which stall propagation occurs in the rotor. (2) In the laminar flow regime, its heat transfer performance at zero rotational speed is superior to forced convection in the triangular, square, annular, rectangular and parallel-plane geometries. (3) The effects of disk surface rotation are twofold: a significant augmentation in heat transfer accompanied by a very substantial reduction in friction loss. (4) These rotational effects decrease with an increase in the fluid flow rate until the transition Reynolds number where the effects of centrifugal and Coriolis forces diminish is reached. (5) Heat transfer performance at low through flows is superior to that of high-performance surfaces for compact heat exchangers.
Lateral Intrusion of Natural Convection into a Horizontal Porous Structure
Authors: Bejan Adrian
Published: October 2009

This article illustrates the fundamental features of lateral penetration of natural convection into a horizontal porous layer in lateral communication with a heat reservoir. It is found that the important group governing the fluid mechanics of the phenomenon is the Darcy-modified Rayleigh number Ra based on longitudinal (horizontal) permeability and on transversal (vertical) thermal diffusivity. It is shown that the buoyancy-driven flow has flattened C-shaped streamlines and isotherms. The flow penetrates laterally to a distance of order H Ra1/2, where H is the height of the porous layer. The net heat exchange between the porous structure and the lateral heat reservoir is described by a Nusselt number result of the type Nu ∼ Ra1/2. The effect of horizontal wall temperature gradient on penetration length and heat transfer is discussed. The engineering importance of these findings is illustrated by examples related to the conceptual design of porous winding structures for rotating superconducting electric machines.
Refilling and Rewetting of a Hot Horizontal Tube: Part II—Structure of a Two-Fluid Model
Authors: Chan A. M. C. , Banerjee S.
Published: October 2009

This is the second paper in a series of three papers reporting on a study on refilling and rewetting of horizontal tubes. The experimental work has been reported in a previous paper (Chan and Banerjee [1]). This paper concentrates on development of a mathematical model for analysis of the main thermal-hydraulic processes. The resulting set of equations are solved numerically. An explicit finite difference characteristics technique is used to solve the hydraulic equations. To assess the model and the accuracy of the numerical technique used, a relatively simple problem, refilling of a dry horizontal tube with no heat transfer, is investigated. Experimental and calculated results are compared. This problem highlights the hydraulic aspects of the more complicated refilling and rewetting problem which is analyzed in a subsequent paper (Chan and Banerjee [2]).
Quenching Studies on a Zircaloy Rod Bundle
Authors: Dhir V. K. , Duffey R. B. , Catton I.
Published: October 2009

Quenching data are presented for reflooding by cold water of zircaloy and stainless steel clad rod bundles. In particular a filling material (Al2O3) with thermophysical properties similar to UO2 is used. The rods which are 1.1 mm in outside diameter and are 1.2 m high are arranged in a square lattice and are inductively heated. The experiments have been performed with initial rod surface temperatures up to 1400 K and flooding velocity varying over the range 1–30 cm/s. The subcooling of water at inlet was either 75 K or 50 K. Under identical flow conditions zircaloy is observed to quench faster than stainless steel. The quenching temperature and quench front velocity are found to increase with liquid subcooling and flooding velocity. The present data have been correlated and compared with existing models and correlations.
Dynamic Simulation of LMFBR Plant under Natural Circulation
Authors: Agrawal A. K. , Madni I. K. , Guppy J. G. , Weaver W. L.
Published: October 2009

Dynamic simulation of the entire LMFBR plant is needed to determine after-heat dissipation capability of the plant via natural circulation. Models required to accomplish this task are briefly described. The resulting computer code, Super System Code-Loop (SSC-L), is then applied to a loop-type fast reactor design to illustrate the system response for a loss-of-electric-power event. Where possible, the Clinch River Breeder Reactor Plant (CRBRP) specifications are used. Entire simulation is performed for up to 1800 seconds of the transient time. Even with rather detailed modeling of essential components, the computing time required on the CDC-7600 machine was slightly less than the real time. For the assumed plant conditions, it is found that the decay heat is adequately removed via natural circulation. The effect of advanced modeling on system performance is also demonstrated. Finally, a scenario of an event that could impose more stringent testing of the plant’s capability for adequate dissipation of decay heat is described.
Use of Scanning Microphotometer to Determine the Evaporative Heat Transfer Characteristics of the Contact Line Region
Authors: Cook R. , Tung C. Y. , Wayner P. C.
Published: October 2009

A scanning microphotometer was used to measure in situ the profile of an evaporating decane meniscus in the contact line region on a smooth inclined silicon substrate as a function of the evaporative heat flux. The use of this new experimental design to determine the effect of heat flux on the profile in the contact line region is discussed. The results support the hypothesis that fluid flow in the contact line region of an evaporating thin film results from a change in the thin film thickness profile.
Effective Thermal Conductivities of Fibrous Composites
Authors: Han L. S. , Cosner A. A.
Published: October 2009

Most composite research to date has been concerned with mechanical properties. However, with anticipated use of composite materials in high temperature aero-space structures and other applications, thermal properties have become essential design information. This paper summarizes the results of a rigorous analysis to determine the steady-state effective thermal conductivities of fiber-matrix type of composites. A principal purpose of the present work is to investigate a class of heat conduction problems for which the proximity effects of the embedded fibers are significant. The fibers are considered dispersed uniformly in a matrix of resin. The dispersion patterns or configurations considered are: (1) uni-directional fibers in a matrix, as the simplest geometry, and (2) 0/90 configuration in which uni-directional tapes are overlaid at 90 deg to each other. The method of analysis is to solve a two-region steady-state heat conduction equation analytically or numerically. The analysis assumes prior knowledge of the geometry and the thermal conductivities of the composite constituents.
Density-Wave Oscillations in Sodium Heated Once-Through Steam Generator Tubes
Authors: U¨nal H. C.
Published: October 2009

Inception conditions of density-wave oscillations were determined in two sodium heated once-through steam generator tubes, i.e., in a 44.43 m long helical coil of 0.018 i.d. and in a tube of 0.0131 m i.d., comprised of a 9.40 m long vertical- and an 11.05 m long, V-shaped horizontal tube. The operating conditions on the water/steam side for the experiments were: pressure: 6–19.1 MN/m2; mass velocity 187–1020 kg/m2 s; inlet subcooling: 3.2–168 K; outlet steam quality: 1.15–2.38. The 306 data obtained and the 74 data found in the literature from sodium and electrically heated once-through steam generator tubes were correlated within 7.5 percent accuracy for 98 percent of the time. The R.M.S. error for all the 380 data is 3.33 percent. The observed density-wave oscillations are time-delay oscillations and the length of the superheated steam region and the transit time in this region practically govern the mechanism of these oscillations. An empirical relation has also been established for this mechanism.
A Numerical Solution to Dropwise Evaporation
Authors: Rizza J. J.
Published: October 2009

A numerical solution is presented for spray evaporation on the surface of a spray evaporator. Excess temperatures below the Leidenfrost transition temperature are considered along with the nonisothermal wall condition. The combination of a high thermal conductivity and low heat capacity for the evaporator wall material, as well as the time-dependent boundary conditions, dictates a quasi-steady-state solution to this evaporator phenomenon. A numerical solution to the conduction equation and boundary conditions is given. A dimensionless evaporation time is computed, and from this a flooding index is developed. The flooding index is shown to be related exponentially to the droplet diameter and wetting ratio. The functional correlation between the heat transfer coefficient for the spray and the wetting ratio is verified from previously published experimental data.
Cooling of Freely Falling Liquid Drops with a Shell of an Immiscible Volatile Liquid
Authors: Mori Yasuhiko H. , Nagai Kyuichiro , Funaba Hitoshi , Komotori Kazunari
Published: October 2009

An augmentation of evaporative cooling of liquid drops falling freely through the atmosphere has been attempted by attaching them with some amount of immiscible volatile liquid. An experimental study was performed for a water/n-pentane system, the water either being pure or containing a small amount of surfactant. The cooling rate was found to be strongly augmented provided the volatile liquid (n-pentane) engulfed almost completely the liquid which was to be cooled (water). The dependences of the cooling rate on the initial drop temperature, volume ratio of the volatile liquid to the other in each drop, air temperature and humidity were examined.
Flow Structure with Natural Convection in Inclined Air-Filled Enclosures
Authors: Linthorst S. J. M. , Schinkel W. M. M. , Hoogendoorn C. J.
Published: October 2009

Flow visualization observations are described for natural convection flow in rectangular inclined enclosures. Observations are made in air-filled enclosures of small and moderate aspect ratio (0.25 ⩽ Ax ⩽ 7), angles of inclination from 0 to 90 deg and Rayleigh number between 5 × 103 and 2.5 × 105. For the range of parameters considered we determined the transition from stationary to nonstationary flow and the transition from two-dimensional to three-dimensional flow. Also, the different stationary flow structures are described. In addition measurements of the velocity profile of the stationary flow have been performed by means of a laser doppler anemometer. Special attention has been given to the side wall boundary condition of the enclosure.
Laminar Mixed Convection in a Shrouded Fin Array
Authors: Acharya S. , Patankar S. V.
Published: October 2009

An analytical study is made to investigate the effect of buoyancy on laminar forced convection in a shrouded fin array. Two heating conditions are considered; in one, the fins and the base surface are hotter than the fluid, and in the other, they are colder. The results are obtained numerically for a wide range of the governing buoyancy parameter. It is found that with a hot fin and base, the secondary flow pattern is mostly made up of a single eddy. The influence of buoyancy is significant and leads to Nusselt numbers and friction factors which are much higher than for pure forced convection. With a cold fin and base, the presence of a tip clearance between the fins and the shroud generates a multiple eddy pattern. The resulting stratification is responsible for the existence of high axial velocity and temperature in the clearance region relative to that in the inter-fin space. Compared to the hot fin case, the secondary flow is weaker, and therefore a relatively smaller increase in the friction factor is obtained. The Nusselt number is found to increase only in the absence of tip clearance. The distribution of the heat transfer coefficient along the fin and the base for both heating situations is found to be highly nonuniform.
Combined Free and Forced Convection in Vertical Tubes with Radial Internal Fins
Authors: Prakash C. , Patankar S. V.
Published: October 2009

An analysis is made of the fully developed laminar flow and heat transfer in vertical tubes with radial internal fins to determine the influence of the buoyancy forces. The governing equations for velocity and temperature are solved by a finite difference technique which incorporates a special scheme for treating the two coupled variables. Results are presented for a range of the Rayleigh number and for various values of the fin height and the number of fins. The buoyancy force is found to increase significantly both friction and heat transfer in the finned tube; augmentation factors in the range of 5 to 10 are encountered. The effect of buoyancy is particularly strong when the number of fins is small and the fins are short.
Some Fundamental Relationships for Tubular Heat Exchanger Thermal Performance
Authors: Singh Krishna P.
Published: October 2009

Some basic relationships to characterize tubular heat exchanger thermal performance are derived in terms of the well-known state variables. It is shown that the knowledge of η (NTU), R (heat capacity rate ratio), and partial derivatives of the temperature efficiency P with respect to η and R enables complete characterization of the exchanger performance around an operating point. Thus, the exchanger performance can be readily predicted for the so-called “subdesign” conditions. Likewise, additional criteria to compare various exchanger styles for a given range of operating conditions can be developed. Two such criteria are developed in this paper.
A Parametric Study of a Particulate Direct Contact Heat Exchanger
Authors: Letan Ruth
Published: October 2009

The function performed by a direct contact heat exchanger is by definition a heat interaction between two media without an interfering wall between them. The direct contact heat exchanger analyzed herein refers to the restricted definition of systems in which temperatures of the contacted media vary without change of phase. This class involves the particulate systems of immiscible liquids, solid particles in fluids, gas bubbles in liquids, and droplets in gases. The applicability of direct contact heat exchangers has been considered for use in fouling and crystallizing systems, sea-water heating, geothermal brines, as well as in nuclear and MHD power plants. An analytic way to evaluate the performance of a direct contact heat exchanger is applied to examine the effects of operational variables upon length and diameter of a heat exchanger. The heat exchanger becomes shorter as the particle size decreases, and heat capacity ratio, flow rate ratio and approach temperature increase. The diameter of the column decreases with the particle size, and the density ratio of the contacted media. It increases with the flow rate ratio. All the evaluations made, correspond to the laminar bulk flow in the heat exchanger, and to particle Reynolds numbers in the range of 20–500.
Heat Transfer in Air Enclosures of Aspect Ratio Less than One
Authors: Sernas V. , Lee E. I.
Published: October 2009

The heat transfer rates inside rectangular air enclosures of aspect ratios between 0.1 and 1.0 were investigated interferometrically for a Grashof number range between 2.64 × 106 and 5.45 × 106. The enclosures were composed of dissimilar temperature vertical walls and two types of ceilings and floors. One type was made from constant temperature plates kept at the vertical wall temperatures, and the other type was made of low thermal conductivity polyurethane foam rubber. The heat transfer characteristics and flow patterns within these two types of enclosures were found to be significantly different. For aspect ratios between 0.4 and 1.0 the isothermal ceiling and floor approximate an adiabatic boundary condition much better than foam because much less heat was interchanged between the floor (or ceiling) and the air in the enclosure.
Natural Convection in Undivided and Partially Divided Rectangular Enclosures
Authors: Nansteel M. W. , Greif R.
Published: October 2009

Heat transfer by natural convection in a two-dimensional rectangular enclosure fitted with partial vertical divisions is investigated experimentally. The horizontal walls of the enclosure are adiabatic while the vertical walls are maintained at different temperatures. The experiments are carried out with water, Pr ≃ 3.5, for Rayleigh numbers in the range, 2.3 × 1010 ⩽ RaL ⩽ 1.1 × 1011, and an aspect ratio, A = H/L = 1/2. The effect of the partial vertical divisions on the fluid flow and temperature fields is investigated by dye-injection flow visualization and by thermocouple probes, respectively. The effect of the partitions on the heat transfer across the enclosure is also studied and correlations for the Nusselt number as a function of RaL and partition length are generated for both conducting and non-conducting partition materials. Partial divisions are found to have a significant effect on the heat transfer; especially when the divisions are adiabatic. The results also indicate that the partial divisions may have a stabilizing effect on the laminar-transitional flow on the heated vertical walls of the enclosure.
Natural Convection Heat Transfer Coefficients for a Short Horizontal Cylinder Attached to a Vertical Plate
Authors: Sparrow E. M. , Chrysler G. M.
Published: October 2009

Experiments were performed to investigate the natural convection heat transfer characteristics of a short isothermal horizontal cylinder attached to an equi-temperature vertical plate. The apparatus was designed so that the cylinder could be attached to the plate at any one of three positions along the height of the plate. Two cylinders were employed (one at a time) during the course of the experiments, one of which had a length equal to its diameter while the other had a length that was half the diameter. At each attachment position and for each cylinder, the Rayleigh number (based on the cylinder diameter) ranged from 1.4 × 104 to 1.4 × 105. It was found that the interaction of the flat plate boundary layer with the cylinder brought about a reduction of the cylinder Nusselt number relative to that for the classical case of the long isolated horizontal cylinder without end effects. The respective deviations of the Nusselt numbers for the shorter and longer of the participating cylinders from the literature correlation for the isolated cylinder were twenty percent and ten percent. At a given Rayleigh number, the cylinder Nusselt number was quite insensitive to the position of the cylinder along the plate, with the typical data spread due to height being in the 5–7 percent range. The Nusselt number was also rather insensitive to cylinder length, showing a ten percent increase as the length-diameter ratio was increased from one-half to one.
An Analytical and Experimental Investigation of Bubble Waiting Time in Nucleate Boiling
Authors: Ali Ameer , Judd R. L.
Published: October 2009

In as much as bubble nucleation theory formulated on the basis of transient conduction to the liquid in the vicinity of the heat transfer surface predicted results for bubble waiting time that were inconsistent with experimental data, a bubble nucleation theory incorporating both conductive and convective heat transfer to the liquid in the wake of a rising bubble was developed. The bubble waiting time results predicted by this theory agreed very well with experimental observations and therefore the evidence suggests that the convective heat transfer contribution is a significant feature of bubble nucleation particularly for subcooled boiling conditions.
A General Extended Surface Analysis Method
Authors: Snider A. D. , Kraus A. D.
Published: October 2009

An earlier paper by the authors presented an algorithm for analyzing certain arrays of extended surface, in terms of the heat transfer properties and geometries of the individual fins comprising the array. This paper identifies the subclass of arrays susceptible to such analysis as trees, in the graph theoretic sense, and extends the technique by deriving general equations for efficiently analyzing a perfectly arbitrary configuration of fins.