bluuebunny/crossref_metadata_2025 huggingface dataset:
Contexts of Mother–Child Separations in Homeless Families
Authors: Barrow Susan M. , Lawinski Terese
Published: April 2009

Families that contend with the losses, disruptions, and hardships occasioned by homelessness often experience dispersal of children as well. Although a federal initiative on homeless families identified family preservation as a focus of intervention development, there is little research to guide service efforts. This qualitative study of mother–child separations in homeless families with maternal mental health and/or substance use problems identifies precursors of separations (precarious housing, turbulent relationships, substance abuse by mothers and others, institutional confinement, and children's needs) and examines how mothers' responses to these events and conditions interact with social and institutional contexts to shape variations in the course and outcome of separations. Implications for research, services, and policies affecting homeless families are discussed.
Echocardiographic Assessment of Conjoined Twins with Congenital Heart Disease in Shanghai
Authors: Zhang Yu‐Qi , Wu Lan‐Ping , Wu Li‐Jun , Chen Guo‐Zhen , Sun Kun , Zhang Zhi‐Fang , Shen Rong
Published: April 2009

Background: The aim of this study is to improve the diagnosis of congenital heart disease in conjoined twins using echocardiography. Methods: Six sets of conjoined twins at Shanghai Children's Medical Center and Xin‐Hua Hospital from 1980 to 2006 were assessed retrospectively. Cardiac anomalies of varying degrees of severity were first evaluated using 2D echocardiography. Tissue Doppler imaging (TDI) was then performed if fused ventricles were suspected. Peak systolic velocities, peak systolic strain rates, and peak systolic strains at the fused myocardium were quantitatively measured using strain rate imaging (SRI). If the M‐mode echocardiographic image was poor or difficult to measure, the myocardial performance index (MPI) of the left ventricle was calculated. Results: Intracardiac anomalies were diagnosed correctly using echocardiography and confirmed by surgical findings. Cardiac functional assessment using MPI demonstrated heart failure in three out of the eight individuals. Subtle conjunction of the ventricles, however, were more difficult to visualize and two sets of conjoined twins with fused hearts could not be clearly demonstrated by echocardiography. In one case of suspected ventricular wall conjunction, TDI showed separate ventricular myocardia which was confirmed at surgery. Conclusions: Intracardiac anomalies and ventricular function can be readily demonstrated by echocardiography, but subtle conjunction of the ventricles may be more difficult to visualize. TDI may be required if there is uncertainty about the degree of cardiac fusion. (ECHOCARDIOGRAPHY, Volume 26, July 2009)
Acute Changes in Cardiac Synchrony and Output According to RV Pacing Sites in Koreans with Normal Cardiac Function
Authors: Yoon Hee Jeoung , Jin Seung Won , Her Sung Ho , Lee Jong Min , Shin Woo Seung , Kim Ji Hoon , Oh Yong Suk , Lee Man Young , Seung Ki Bae , Rho Tai Ho , Kim Jae Hyung
Published: April 2009

Introduction: The synchrony of the pacing heart can be affected by the right ventricular (RV) pacing site and is crucial to cardiac function in pacemaker recipients. We evaluated the acute changes in cardiac synchrony according to the RV pacing sites in normal systolic functioning subjects with normal QRS. Methods: We conducted this study with 30 patients with the pacing in the RV apex (RVA), RV septum (RVS), and RV outflow tract (RVOT) in a sequential manner
. Transthoracic echocardiography was conducted at rest and during pacing in order to measure interventricular and intraventricular dyssynchrony in all patients. Results: QRS duration (148.1 ± 12.8 ms) of RVA pacing was significantly shorter than that of RVS pacing (154.4 ± 14.1 ms, P < 0.01) and RVOT pacing (160.6 ± 15.7 ms, P < 0.001). We noted no statistically significant difference in cardiac output according to the pacing sites. The interventricular dyssynchrony with M‐mode and Doppler echocardiography in RVOT pacing was increased to an insignificant degree as compared with those with RVS pacing or RVA pacing. The intraventricular dyssynchrony with tissue Doppler echocardiography in RVA pacing was reduced significantly as compared with that of RVS pacing or RVOT (RVA = 60.3 ± 32.7 ms, RVS = 82.1 ± 33.8 ms, RVOT = 79.1 ± 33.3 ms; RVA vs RVS = P < 0.05, RVA vs RVOT = P < 0.01, RVS vs RVOT = P = NS). Conclusion: RVA pacing is superior to RVS and RVOT pacing with regard to intraventricular synchrony in normal systolic functioning subjects with normal QRS. Cardiac output at RVA pacing is not inferior to other sites. (ECHOCARDIOGRAPHY, Volume 26, July 2009)
Resting Myocardial Velocity Gradient Is a Reliable Measurement That Identifies Viable Myocardium
Authors: Rayan Mona Mostafa
Published: April 2009

In the setting of coronary artery disease, two‐thirds of LV dysfunction is not the result of irreversible scar, but rather caused by impairment in function and energy use of “still‐viable” myocyte. The opportunity for improved function, if coronary blood flow is restored, is there which makes the identification of viable myocardium important. Purpose: The purpose of this study is to identify the value of resting myocardial velocity gradient (MVG) in detecting viable myocardium in patients with healed anterior wall myocardial infarction (MI). Patients and methods: The study included 30 patients with healed anterior MI, who were submitted to conventional echocardiography and tissue Doppler for measurement of MVG. Myocardial perfusion scan using Technetium (Tc)‐99m was the gold standard test for the detection of viability. Ten healthy control subjects were also included to obtain reference values for MVG. Results: Resting MVG was able to differentiate infarct regions, and to detect viable myocardium compared to Tc‐99m studies (0.68 ± 0.2 vs 0.49 ± 0.22) P < 0.01. Conclusion: MVG provides quantitative assessment of the regional wall thickening that help localizing the infarct zone and detecting viable myocardium at rest. (ECHOCARDIOGRAPHY, Volume 26, July 2009)
Validation of a multivariate prediction rule for history of periodontitis in a separate population
Authors: Dietrich Thomas , Kaiser Walter , Naumann Michael , Stosch Ulrike , Schwahn Christian , Biffar Reiner , Dietrich Dieter , Kocher Thomas
Published: April 2009

Aim: Validation of a previously derived prediction rule for periodontitis in an external population sample.

Materials and Methods: Age, smoking and self‐reported tooth mobility were used in logistic models to predict moderate and severe periodontitis as diagnosed from panoramic radiographs of 246 patients attending private practices in Germany. Coefficients derived from these models were used to predict periodontitis in a representative population‐based sample of 3297 residents of the region of Pomerania, Germany.

Results: In the full derivation sample, the predictive power of the logistic model as measured by the c‐statistic was 0.82 and 0.84 for moderate and severe periodontitis, respectively. In the validation set, these models yielded c‐statistics of 0.82 for both moderate and severe periodontitis. Lower c‐statistics were obtained among subjects aged 40 years and older in the derivation set (c=0.74 and 0.77), and the performance was poorer in the validation set with c‐statistics of 0.69 and 0.72, respectively.

Conclusions: A prediction rule based on age, smoking and self‐reported tooth mobility can yield a moderately useful external validity. Validity may be dependent on specific population characteristics, and derivation of a prediction rule based on a clinical subsample of the target population with a larger set of predictors may provide better results in an application.
Electron paramagnetic resonance as a unique tool for skin and hair research
Authors: Plonka Przemyslaw M.
Published: April 2009

Abstract:  Electron paramagnetic resonance (EPR) spectroscopy and imaging (EPRI) are deeply rooted in the basic and quantum physics, but the spectrum of their applications in modern experimental and clinical dermatology and cosmetology is surprisingly wide. The main aim of this review was to show the physical foundation, technical limitations and versatility of this method in skin studies. Free radical and metal ion detection, EPR dosimetry, melanin study, spin trapping, spin labelling, oximetry and NO‐metry, EPR imaging, new generation methods of EPR and EPR/NMR hybrid technology used under ex vivo and in vivo regime are portrayed in the context of clinical and experimental skin research to study problems such as oxidative and nitrosative stress generated by UV or inflammation, skin oxygenation, hydration of corneal layer of epidermis, transport and metabolism of drugs and cosmeceutics, skin carcinogenesis, skin tumors and many others. A part of the paper is devoted to hair and nail research. The review of dermatological applications of EPR is supplemented with a handful of advice concerning practical aspects of EPR experimentation and usage of EPR reagents.
A probabilistic approach to estimating species pools from large compositional matrices
Authors: Ewald Jörg
Published: April 2009

Abstract. Species pools are increasingly recognized as important controls of local plant community structure and diversity. While existing approaches to estimate their content and size either rely on phytosociological expert knowledge or on simple response models across environmental gradients, the proposed application of phytosociological smoothing according to Beals exploits the full information of plant co‐occurrence patterns statistically. Where numerous representative compositional data are available, the new method yields robust estimates of the potential of sites to harbour plant species.

To test the new method, a large phytosociological databank covering the forested regions of Oregon (US) was subsampled randomly and evenly across strata defined by geographic regions and elevation belts. The resulting matrix of species presence/absence in 874 plots was smoothed by calculating Beals' index of sociological favourability, which estimates the probability of encountering each species at each site from the actual plot composition and the pattern of species co‐occurrence in the matrix. In a second step, the resulting lists of sociologically probable species were intersected with complete species lists for each of 14 geographical subregions. Species pools were compared to observed species composition and richness. Species pool size exhibited much clearer spatial trends than plot richness and could be modelled much better as a function of climatic factors. In this framework the goal of modelling species pools is not to test a hypothesis, but to bridge the gap between manageable scales of empirical observation and the spatio‐temporal hierarchy of diversity patterns.
An Alternative Method for Constructing an Obturator Prosthesis for a Patient with a Bilateral Cleft Lip and Palate: A Clinical Report
Authors: GÜMÜŞ HASAN ÖNDER , TUNA SÜLEYMAN HAKAN
Published: April 2009

The design of esthetic and effective dental prostheses for bilateral cleft lip and palate patients is a challenge for prosthodontists because the prostheses must serve more than one purpose. The goals to be attained by prosthetic intervention are preventing food and liquid leakage into the nose, improving speech intelligibility, a more esthetic appearance, and achieving the general satisfaction of the patient. The framework design of the obturator prosthesis is of great strategic importance for patients with a cleft lip and palate. The reduction in the mass of the obturator prosthesis increases stabilization and retention and also contributes to an easier adaptation to the prosthetic restoration. In this report, a 22‐year‐old woman was successfully treated with a fixed partial denture and a bar‐retained obturator with palatal coverage.

CLINICAL SIGNIFICANCE

The design of an obturator prosthesis for cleft lip and palate patients is an important stage in terms of ensuring esthetic restoration and patient comfort. This article describes an esthetic and functional design for such a device using a fixed partial denture and a bar‐retained obturator.
Gingival Zenith Positions and Levels of the Maxillary Anterior Dentition
Authors: CHU STEPHEN J. , TAN JOCELYN H‐P. , STAPPERT CHRISTIAN F.J. , TARNOW DENNIS P.
Published: April 2009

Purpose:  The location of the gingival zenith in a medial‐lateral position relative to the vertical tooth axis of the maxillary anterior teeth remains to be clearly defined. In addition, the apex of the free gingival margin of the lateral incisor teeth relative to the gingival zeniths of the adjacent proximal teeth remains undetermined. Therefore, this investigation evaluated two clinical parameters: (1) the gingival zenith position (GZP) from the vertical bisected midline (VBM) along the long axis of each individual maxillary anterior tooth; and (2) the gingival zenith level (GZL) of the lateral incisors in an apical‐coronal direction relative to the gingival line joining the tangents of the GZP of the adjacent central incisor and canine teeth under healthy conditions.

Materials and Methods:  A total of 240 sites in 20 healthy patients (13 females, 7 males) with an average age of 27.7 years were evaluated. The inclusion patient criteria were absence of periodontal disease, gingival recession, or gingival hypertrophy as well as teeth without loss of interdental papillae, spacing, crowding, existing restorations, and incisal attrition.

GZP dimensions were measured with calibrated digital calipers for each individual tooth and within each tooth group in a medial‐lateral direction from the VBM. GZLs were measured in an apical‐coronal direction from a tangent line drawn on the diagnostic casts from the GZPs of the adjacent teeth.

Results:  This study demonstrated that all central incisors displayed a distal GZP from the VBM, with a mean average of 1 mm. Lateral incisors showed a deviation of the gingival zenith by a mean of 0.4 mm. In 97.5% of the canine population, the GZP was centralized along the long axis of the canine. The mean distance of the contour of the gingival margin in an apical‐coronal direction of the lateral incisors (GZL) relative to gingival line joining the tangent of the adjacent central and canine GZPs was approximately 1 mm.

Conclusion:  This investigation revealed a GZP mean value of 1 mm distal from the VBM for the central incisor tooth group. The lateral incisors showed a mean average of 0.4 mm. Thecanine tooth group demonstrated almost no deviations of the GZP from the VBM. The GZL of the lateral incisors relative to the adjacent central incisor and canine teeth were more coronal by approximately 1 mm. These data could be used as reference points during esthetic anterior oral rehabilitation.

CLINICAL SIGNIFICANCE

The information presented in this article can be clinically applied to reestablish the proper intratooth GZPs of the maxillary anterior teeth during periodontal crown lengthening or root coverage procedures. In addition, the intra‐arch gingival level of the lateral incisor gingival zenith relative to the adjacent central and canine teeth can be appropriately established.
Temperature Changes in Silorane‐, Ormocer‐, and Dimethacrylate‐Based Composites and Pulp Chamber Roof during Light‐Curing
Authors: MILETIC VESNA , IVANOVIC VLADIMIR , DZELETOVIC BOJAN , LEZAJA MAJA
Published: April 2009

Statement of the Problem:  Light‐curing of resin‐based composites (RBCs) is associated with temperature increase in the pulp chamber, which may have a detrimental effect on the vital pulp.

Purpose:  The purpose of the study was to evaluate temperature changes of silorane‐, ormocer‐, and dimethacrylate‐based RBCs at the bottom surface of the RBC and in the pulp chamber roof dentin (PCRD) during curing.

Materials and Methods:  In part A, temperatures were measured for Filtek LS (3M ESPE, St. Paul, MN, USA), Admira (Voco GmbH, Cuxhaven, Germany), and Herculite XRV (Kerr Corp., Orange, CA, USA) with a high‐power light‐emitting diode (LED) unit by placing thermocouples in contact with the bottom surface of the material in standardized acrylic molds. In part B, temperature changes in PCRD were measured in extracted molars during light‐curing of adhesives and RBCs in 2‐mm‐deep cavities with a remaining dentin thickness (RDT) of 1 mm.

Results:  Filtek LS showed a different temperature curve compared with Admira and Herculite XRV. Significantly higher temperatures were recorded for Filtek LS (p < 0.001) than for Admira and Herculite XRV in acrylic molds. Temperature rises recorded in PCRD for adhesives and RBCs were between 4.1 and 6.4°C. No significant differences in PCRD temperatures were found between the three groups during adhesive curing and RBC curing (p > 0.05).

Conclusions:  Filtek LS showed a different heat‐generation pattern from and significantly higher temperatures than Admira and Herculite XRV when the materials were tested in acrylic molds. Similar temperatures were recorded in the PCRD during curing of adhesives and RBCs.

CLINICAL SIGNIFICANCE

Although a substantial temperature rise in the bulk material occurred during light‐curing of the three resin‐based composites, a remaining dentin thickness of 1 mm caused a significant reduction in pulp chamber roof dentin temperatures. Temperatures measured in the pulp chamber roof dentin corresponding to the zone occupied by the postmitotic odontoblast layer were not statistically different for the three types of resin‐based composites.
Shakespeare and the Senses
Authors: Dugan Holly
Published: April 2009

This article examines recent critical approaches to Shakespeare and the senses. Historicizing the senses has posed certain methodological challenges: what is the relationship between subjective sensory perceptions and broader cultural understandings of sensation? Does the sensate have a history? Recent work on each of the five senses demonstrates that the answer is yes. And, surprisingly, Shakespeare and his literary works are at the center of the field. As an important figure of the English literary canon, yet one about whom we know so very little, Shakespeare's sensory archive is both omnipresent and illusive. Shakespearean sensations thus provide a way of grappling with the larger methodological stakes of this field. This article examines a wide range of critical approaches to Shakespeare's sensory archive and ends by considering possible paths for further research.
Development and characterization of 30 polymorphic microsatellite markers for the Atlantic surfclam, Spisula solidissima (Dillwyn, 1817)
Authors: WANG YAN , WANG AIMIN , GUO XIMING
Published: April 2009

Thirty polymorphic microsatellite markers were developed for the Atlantic surfclam, Spisula solidissima, from an enriched library and characterized in 24 clams from a wild population. The number of alleles ranged from 3 to 16 per locus. The expected and observed heterozygosities ranged from 0.1942 to 0.9238 and 0.0833 to 0.875 respectively. Six loci showed significant (P < 0.05 after Bonferroni correction) deviation from Hardy–Weinberg equilibrium, probably because of the presence of null alleles. Three primer pairs amplified duplicated loci with two involving tandem mini‐satellite repeats. Most of the microsatellite markers developed here should be useful for genetic studies in this species.
Treatment of nonalcoholic steatohepatitis with colestimide
Authors: Taniai Makiko , Hashimoto Etsuko , Tobari Maki , Yatsuji Satoru , Haruta Ikuko , Tokushige Katsutoshi , Shiratori Keiko
Published: April 2009

Aim:  To clarify the usefulness of colestimide in patients with nonalcoholic steatohepatitis (NASH) with hyperlipidemia.

Methods:  In an open‐label randomized controlled trial, 17 NASH patients with hyperlipidemia received colestimide (3 g/day) for 24 weeks. There were 21 control patients. All patients received lifestyle modification therapy. Efficacy was assessed based on metabolic profile, insulin resistance, transaminases, serum hepatic fibrosis markers, adipokine levels, visceral fat on computed tomography (CT), and the fatty liver grade on CT. NASH patients with moderate to severe steatosis by histology were also evaluated separately.

Results:  Baseline clinical characteristics of the two groups were similar. Both groups experienced a significant decrease of BMI with no difference between them. However, visceral fat decreased significantly more in the colestimide group (P = 0.046). Aspartate aminotransferase (AST) showed a significantly greater decrease in the colestimide group compared with the control group (P = 0.042). In patients with moderate to severe histological steatosis, there were significant differences between the two groups regard to HbA1c, transaminases, and hyaluronic acid (P = 0.018 for HbA1c, P = 0.003 for AST, P = 0.042 for alanine aminotransferase, and P = 0.042 for hyaluronic acid). Steatosis significantly improved in patients in the colestimide group who had fatty liver on CT (P = 0.049). In the colestimide group, abdominal distension and/or constipation were seen, but mostly tolerable, no other clinical or laboratory adverse events associated with the use of this medicine were not observed.

Conclusions:  Colestimide seems to increase the efficacy of lifestyle modification in NASH patients with hyperlipidemia. Its beneficial effects were more prominent in NASH patients with moderate to severe histological steatosis.
Asymptotic Theories of Large-Scale Motion, Temperature, and Moisture Distribution in Land-Based Polythermal Ice Sheets: A Critical Review and New Developments
Authors: Baral Dambaru Raj , Hutter Kolumban , Greve Ralf
Published: April 2009

A review is given of the theory of polythermal ice sheets, ie, ice masses of which the ice has submelting temperatures in certain subdomains and is at the pressure melting point in other subdomains. Cold ice is treated as a non-linearly viscous heat conducting fluid, temperate ice as a mixture of ice at the melting point and melt-water diffusing through the ice matrix. Cold and temperate ice are separated by a non-material singular Stefan-type surface. We repeat and partly amend the complicated field equations and boundary conditions as derived in the literature. These equations are subjected to a scale analysis that makes the creeping flow conditions and the shallow geometries of land-based ice sheets explicit. The small aspect ratio ε — typical depth to horizontal distance over which the geometry and/or stresses change appreciably — suggests a perturbation approach for a possible analytical or numerical solution which has been pursued to include second-order terms O(ε2). The lowest-order O(ε0) model equations, known as the shallow-ice approximation (SIA), are asymptotically valid in the entire ice sheet domain except a small marginal zone provided the topographic variations are shallow, ie, possess wave height to wavelength ratios that are O(ε1) and the constitutive relation for the stress deviator exhibits finite viscosity at zero effective shear stress (square root of second stress deviator invariant). We critically review earlier procedures and put them into the proper perspectives with regard to the original expansion procedures. We extend the zeroth-order theory to first and second order but present only those equations and deductions from them which lead to improved physical insight. In particular we derive stress formulas which show how the stresses depend on i) depth and surface slope, ii) surface topography and iii) stress deviator components, more complete than, and going beyond, known formulas of the literature. Finally we discuss numerically computed second-order stresses for the present state of the Greenland ice sheet. It turns out that they are typically three orders of magnitude smaller than the corresponding zeroth-order quantities, and that they are mainly determined by contributions due to zeroth-order stress deviators, rather than by topography effects. Their relative importance is largest close to the ice surface for the second-order pressure, and in the vicinity of ice domes for the horizontal, bed-parallel shear stresses. There are 229 references.
Numerical Simulation on Heat Transfer of Falling Film Flow Along a Vertical Wall
Authors: Kino Chiaki , Kunugi Tomoaki , Kawara Zensaku
Published: April 2009

Numerical simulations based on the MARS (Multi-interface Advection and Reconstruction Solver) developed by one of the authors have been performed in order to understand the heat transfer mechanism of falling film flows along a vertical wall. In the present study, we focused on an internal structure, i.e. velocity profile and heat transfer. In this study, the velocity profiles in a falling film are categorized into three regions: substrate film region, solitary wave region, and capillary wave region with each characteristic. Moreover, small vortices can be found in the capillary wave region. Additionally, numerical results indicate that heat transfer mechanism is different for these three regions. We proposed new heat transfer evaluation manner as a function of the Prandtl number for these regions. This manner could contribute to a design work of falling film flow device.
A Conjugate Model for Hepatic Cancer Cryosurgery Using a Liquid-Nitrogen Cryorobe
Authors: Sun Feng , Wang G.-X.
Published: April 2009

Cryosurgery is a surgical technique using low temperature cryogen to achieve selective tissue destruction by freezing. During cryosurgery, the cryoprobe, which is usually cooled by inner circulation of liquid nitrogen (LN2), is inserted into the targeted tumor tissue. The tissue surrounding the cryoprobe is then cooled down to sub-zero temperature and subsequently frozen. Extensive studies have been conducted to understand the mechanism of tissue injury, and various numerical models have been developed to predict the thermal history of the targeted tissues during cryosurgery. Most of the existing models, however, focused on the tissue freezing and applied simplified thermal boundary conditions at the interface between cryoprobe and surrounding tissue, e.g. a constant temperature or a constant heat flux. This paper presents a conjugate model for cryosurgery. The new model treats with both tissue freezing outside of the cryoprobe and turbulent convective heat transfer of LN2 inside the cryoprobe. The thermal condition along the cryoprobe surface is then part of the solution, instead of a presumption. The turbulent convection of single phase LN2 inside the cryoprobe is described by a Realizable κ-ε model, while the Pennes equation is used to address the heat transfer within the hepatic tissue. An apparent heat capacity method is used to deal with tissue freezing. As an example, the model is used to simulate the hepatic cryosurgery with a single cryoprobe. The model predicts a dynamic, non-unform surface temperature along the cryoprobe surface, which shows a large effect on the ice ball formation outside the cryoprobe. Results are also presented to illustrate the effect of the flow condition and the cryoprobe design on the interface thermal condition in cryosurgery.
Assessment of a Second-Moment Closure Model for Strongly Heated Internal Gas Flows
Authors: Spall Robert E. , Nisipeanu Eugen , Richards Adam
Published: April 2009

Both low- and high-Reynolds-number versions of a stress–ω turbulence model were applied to the vertical flow of air through a tube with high wall heat flux boundary conditions. Heating rates were sufficiently high so that fluid properties varied significantly, and consequently fully developed flows did not result. Solutions were compared against experimental data existing in the literature. The results revealed that the inclusion of low-Reynolds-number corrections were necessary to achieve reasonable agreement with experiments in terms of predicted wall temperatures, and mean axial velocity and temperature profiles.
Nucleate Boiling Heat Transfer Under Liquid Jet Impingement
Authors: Omar Ahmed M. T. , Hamed M. S. , Shoukri M.
Published: April 2009

Liquid jet impingement is a very effective way of cooling of simple and complicated geometry objects. The attainable cooling rate is radically enhanced when using liquids as coolant due to the possibility of having boiling to occur during the impingement process. Bubble activity on the surface and the resulted mixing with the fluid bulk produces an additional factor of enhancement which at some levels of surface temperature dominates other convective mechanism due to the coolant flow perpendicular or parallel to the surface. The efficient nucleate boiling heat transfer regime can be divided into: partial nucleate boiling and fully developed nucleate boiling. The heat transfer capacity of each and the range of surface temperature over which each of these two boiling regimes up to the critical heat flux (CHF) are experimentally investigated in this research for different coolant temperature and velocity. For this purpose, single planar jet is used to provide the cooling medium of a flat surface that is being heated steadily. The boiling surface temperature was thus controlled by a feed back computer program to allow for steady state operation. So, at each level of boiling surface temperature observation of boiling mode and heat transfer mechanisms was elongated and verified. The experiments were conducted using degassed water jet velocity range between 0.75 and 1.7 m/s and degree of sub-cooling range from 10 to 28 °C at atmospheric pressure. The variation of the heat flux with those factors at different surface superheat up to the CHF point is presented. A physical interpretation is introduced to explain the effects of the input parameters on the heat transfer changes in these regimes.
Thermal Fluid Interaction in a Periodically Heated Capillary
Authors: Huang X. Y. , Jiao Z. J. , Nguyen N. T.
Published: April 2009

This paper reports an experimental study on reciprocating thermocapillary motion of a liquid plug in an externally heated glass capillary. The results were qualitatively compared with that from an analytical modeling. In the experiments, a liquid plug in a glass capillary was positioned between two heaters which were activated alternatively. The liquid plug was driven by the surface tension difference generated by the temperature gradients. The periodic temperature gradients generated by the two heaters made the liquid plug to move back and fort. This method has a potential in manipulating not only the plug motion but also the flow field inside the plug. The position of the plugs was captured and evaluated using a CCD camera. The plug position and maximum traveling distance were measured under various switching frequencies, and the results were recorded as time series for the dynamic analysis. The temperature variation between the heaters depended on the heating process, also depended on the liquid plug motions. An infra thermal camera was used to observe and record the capillary surface temperature when the liquid plug oscillated. A simple model was established for the liquid plug oscillation in the capillary under the periodical heating. The measured liquid plug motion and the temperature variations were compared with predicted results from the model.
Effect of Non-Uniform Clamping Pressure on PEM Fuel Cell Stack Performance
Authors: Fekrazad N. , Bergman T. L.
Published: April 2009

A three-dimensional model of a Proton Exchange Membrane fuel cell stack is developed. Taking advantage of the geometrical periodicity of a typical stack assembly, the model is used to predict the thermal, humidity, and electrochemical distributions within the fuel cell. Of particular interest is the effect of the compressive force used to assemble the stack on the fuel cell’s (a) power output and (b) internal temperature distribution. Application of non-uniform clamping pressure is considered, and predictions suggest that thermal conditions within the stack can be made more uniform with negligible impact on the fuel cell power. Hence, improved fuel cell stack durability might be achieved through judicious application of non-uniform clamping pressures for stack assembly.
Effect of Hole Shape on Flow Resistance of Perforated Plates for Natural Air Cooled Electronic Equipment
Authors: Koizumi Katsuhiro , Ishizuka Masaru , Nakagawa Shinji
Published: April 2009

This paper describes the effect of hole shape on the flow resistance of perforated plates used in electronic equipment in the low Reynolds number region such as natural convection. Measurement of 16 types of perforated plates and analysis of the results were conducted using the Design of Experiments (DoE) method. In the range of levels of DoE analysis assumed for electronic equipment, it was found that hole shape has little effect on flow resistance in the low Reynolds number region.
Microscopic Approaches to Decomposition and Burning Processes of a Micro Plastic Resin Particle
Authors: Yamamoto Atsunori , Yamakita Ryuji , Ishino Yojiro , Ohiwa Norio
Published: April 2009

From a fundamental and microscopic viewpoint to elucidate the possibility and availability of thermal recycling of wasted plastic resin, a series of heating processes of melting, thermal decomposition and burning of a spherical micro plastic resin particle having a diameter of about 200 μm are observed, when it is suddenly exposed to hot oxidizing combustion gas. Three ingenious devices are introduced; the first is a high-speed microscopic direct and schlieren system, the second is a pre-mixed mini-burner for abrupt heating, which is equipped with a pair of spark gaps at its exit and is discharged synchronously with the starting signal of high-speed camera, and the third is a single mini-puff generator, which enables to extinguish instantly all flames around the micro particle at an arbitrary assigned time after the spark ignition. Polyethylene terephthalate and polyethylene are used as two typical plastic resins. In this paper the dependency of internal and external appearances of residual plastic embers on the heating time and the initial plastic composition is optically analyzed, along with appearances of internal micro bubbling, micro jets and micro diffusion flames during abrupt heating. Based on temporal variations of the surface area of a micro plastic particle, the burning rate constant is also evaluated and compared with well-known volatile liquid fuels.
A Study on Flow Patterns and Pressure Drop in Adiabatic Two-Phase Flow Across a Bank of Micro Pin Fins
Authors: Krishnamurthy Santosh , Peles Yoav
Published: April 2009

Flow patterns, void fraction and pressure drop in adiabatic nitrogen-water two phase flows across a bank of micro pin fin were experimentally investigated for Reynolds number ranging from 5 to 50. Staggered cylindrical shaped micro pin fins with diameter and height of 100 μm were micro-fabricated into 1 cm long, 1.8 mm microchannel. Flow patterns were determined by flow visualization and classified as bubbly-slug flow, gas-slug flow, bridged flow and annular flow. The applicability of conventional scale models to predict two-phase frictional pressure drop was also assessed. The two-phase frictional multiplier was found to be a strong function of mass flux and flow patterns unlike the previous results observed in the microchannel studies. It was observed that models from conventional scale systems did not adequately predict the two-phase frictional multiplier at micro-scale and thus, a modified model accounting for mass flux and flow patterns have been developed in this work.
Numerical Simulation of the Coordination Between Velocity and Temperature Fields for Air Flow Across Staggered Elliptic Tube Bundles
Authors: Wang Yangjun , Deng Xianhe , Huang Debin
Published: April 2009

The coordination between the velocity and temperature fields in 2-D developed turbulent flow is analyzed for air across the staggered elliptic tube bundles by means of numerical simulation. The results indicate that the convective heat transfer performance is dominated by the degree of coordination between the velocity and temperature fields. Furthermore, the included angle β between the dimensionless velocity and dimensionless temperature gradient vectors is one of the important factors to control the coordination. The field coordination can be improved by adjusting the include angle β, subsequently the heat transfer can be enhanced effectively. Field coordination principle promotes the development of heat transfer research in a controllable direction.
Thermal Vacuum Testing of a Miniature Loop Heat Pipe With Multiple Evaporators and Multiple Condensers
Authors: Ku Jentung , Ottenstein Laura , Nagano Hosei
Published: April 2009

This paper describes thermal vacuum testing of a miniature loop heat pipe (MLHP) with two evaporators and two condensers designed for future small systems applications requiring low mass, low power and compactness. Each evaporator contains a wick with an outer diameter of 6.4 mm, and each has its own integral compensation chamber (CC). Multiple evaporators provide flexibility for placement of instruments that need to be maintained at the same temperature, and facilitate heat load sharing among instruments, resulting in a reduced auxiliary heater power requirement. A flow regulator is used to regulate heat dissipations among all condensers, thus providing flexibility for placement of radiators on the spacecraft. A thermoelectric converter (TEC) is attached to each CC for operating temperature control and enhancement of start-up success. Tests performed include start-up, power cycle, sink temperature cycle, high power and low power operation, heat load sharing, and operating temperature control. The MLHP demonstrated excellent performance in the thermal vacuum environment. The loop started successfully and operated stably under various evaporator heat loads and condenser sink temperatures. The TECs were able to maintain the loop operating temperature within ±0.5K of the desired set point temperature at all power levels and all sink temperatures. The un-powered evaporator would automatically share heat from the other powered evaporator. The CC control heater power was reduced by more than 50 percent when a TEC was used instead of conventional electrical heaters. The flow regulator was able to regulate the heat dissipation among the radiators and prevent vapor from flowing into the liquid line.
Thermal Properties of Microcrystalline Cellulose Derived Carbons
Authors: Rhim Yo-Rhin , Zhang Dajie , Nagle Dennis C. , Rooney Michael , Herman Cila
Published: April 2009

The thermal transport properties were studied for carbons produced by the carbonization of microcrystalline cellulose. Thermal diffusivity, specific heat, and thermal conductivity were measured via flash method for cellulose derived carbons prepared at various heat treatment temperatures ranging from 250°C to 1000°C. The thermal diffusivity as a function of increasing heat treatment temperature was observed to have four distinct linear regions, which could be related directly to the microstructures of the materials generated by the specific heat treatment temperature. Specific heat values indicated the coexistence of polar and non-polar phases in both partially carbonized materials obtained at lower heat treatment temperatures and fully carbonized materials formed at higher heat treatment temperatures. For partially carbonized materials, the polar groups consisting of residual hydroxyl and carboxyl were still present. For fully carbonized materials, the polar phases have largely been volatilized and conductive nano-carbon clusters were nucleated and observed to grow in an amorphous carbon bed until percolation effects were observed. Such structural characteristics are well supported by FT-IR characterizations. Lastly, a linear relationship between testing temperature and thermal conductivity indicates boundary scattering between highly conductive carbon clusters as the main mechanism for heat conduction.
Measurements of Solar Optical Properties of Transparent Insulation Materials
Authors: Zhu Qunzhi , Duan Rui , Li Yongguang
Published: April 2009

Transparent insulation materials have been extensively used in building windows and solar collector covers. Glass and plastic sheets are long-established insulators while aerogel is a promising material due to its high light transmittance and low thermal conductivity. Optical properties of aerogels, glass, and plastic sheets are measured with a spectrophotometer. Solar transmittance and light transmittance are calculated from the measured optical properties in accordance with the standard spectral data. Normal-direct transmittances and normal-hemispherical transmittances of different materials are compared. Specific surface area and pore size distribution of aerogels are measured with the Brunauer-Emmett-Teller method. The correlation between the optical properties and nanoscale structure features of aerogels is investigated.
Enhancement of Heat Transfer Behind Sliding Bubbles
Authors: Figueroa Marcelino , Hollingsworth D. Keith , Witte Larry C.
Published: April 2009

The time-dependent temperature distribution on an inclined, thin-foil uniform-heat-generation heater was used to infer the surface heat transfer enhancement caused by the passage of an FC-87 bubble sliding beneath the lower surface of the heater. A two-camera system was used: one camera recorded color images of a liquid crystal layer applied to the upper (dry) side of the heater while a second camera simultaneously recorded the position, size, and shape of the bubble from below. The temperature response of the heater could then be correlated directly to the bubble characteristics at any given time during its passage. Data along the line bisecting the bubble wake from 9 bubbles comprising 54 bubble images were analyzed. Heat transfer in the wake behind sliding cap-shaped bubbles is very effective compared to the natural convection that occurs before the passage of the bubble. Maximum values of heat transfer coefficient in the range of 2500 W/m2K were produced in very sharply peaked curves. The point of maximum cooling measured as a fraction of the local driving temperature difference before the bubble passage was identified and correlated with some success to the streamwise length of the bubble. The location of the maximum heat transfer coefficient was reasonably correlated to bubble width. The level of the maximum heat transfer coefficient when cast as a Nusselt number based on bubble width grew to a saturation value as the bubble moved across the plate. A constant value of Nusselt number requires that the heat transfer coefficient falls as the bubble grows past some critical bubble size. This behavior was observed for the larger bubbles.
Thermal Interface Resistances in Nanostructures
Authors: Panzer Matthew , Goodson Ken
Published: April 2009

Nanostructured electronic and photonic devices include a high density of material interfaces, which can strongly impede heat conduction and influence performance and reliability. Thermal conduction through interfaces is a very mature field as long as the interface dimensions are large compared to the phonon wavelength. In nanostructures, however, the confinement of phonons in the directions parallel to the interface may strongly influence heat conduction. The present work investigates a model problem consisting of an abrupt junction between a harmonic 1D and 2D square lattice. The results show that energy couples to phonon modes localized near the free surface and that the energy transmission coefficient across the interface into these surface modes is less than unity even for materials with identical bulk impedances. The lattice dynamics calculations performed here provide an initial perspective on the impact of phonon confinement on the acoustic mismatch resistance and lay the groundwork for more detailed studies involving 3D molecular dynamics.
Heat Exchanger Analysis Modified to Account for a Heat Source
Authors: Narayanan Vinod , Kanury Murty , Jenks Jeromy
Published: April 2009

The practice of determining the overall heat transfer coefficient using the classical definition of log-mean-temperature-difference in heat exchangers with a heat source term in the hot fluid stream is questioned. The motivation for this work arises from the heat exchanger analysis of an ammonia-water absorber heat exchanger where a heat-of-absorption source term arises in the solution side. A modified heat exchanger analysis is developed here with account for such a heat source. Results of the analysis are discussed and its utility in deducing the overall heat transfer coefficient from experimental measurements is demonstrated.
Convective Heat Transfer in a Channel in the Presence of Solid Particles
Authors: Khiabani Reza H. , Joshi Yogendra , Aidun Cyrus
Published: April 2009

In this paper, the effect of cylindrical solid particles suspended in liquid on the rate of heat transfer in a channel is studied. The computational method is based on the lattice-Boltzmann method for the fluid flow and the energy equation. The effects of Reynolds number, particle-to-channel size ratio, location of the particle, and the eccentricity of the particle on heat transfer from the channel walls are considered. The effect of moving particles is also considered on the heat transfer enhancement by simulating several suspended particles moving with the fluid. This latter condition represents a case with solid particles suspended in the cooling medium such as in micro/nanofluids. The results provide insight in the mechanism by which suspended particles can effectively change the rate of heat transfer in a channel. The local and average wall Nusselt numbers are presented for these conditions.
Thermal Conductivity and Specific Heat Capacity of Carbon Nanotube Bundles
Authors: Shelton John , Pyrtle Frank
Published: April 2009

Carbon nanotubes (CNTs) have been thoroughly documented to demonstrate superior heat transfer properties. It has also been determined that these properties decrease substantially as overall dimensions increase from the nanoscale to the microscale. Using non-equilibrium molecular dynamics simulations and finite element analysis, the influence of both internal and external thermal boundary resistance effects on the thermal conductivity and specific heat capacity of single walled carbon nanotube bundles were investigated. Comparisons were made between accepted property values for single CNTs and for CNT bundles. Also, energy transfer between varying sized bundles of single-walled carbon nanotubes (SWCNTs) and a surrounding pressure-driven Lennard-Jones (LJ) fluid were calculated.
Molecular Dynamics Simulation of Thermal Conductivity of Nanocrystalline Composite Films
Authors: Roberts N. A. , Walker D. G. , Li D. Y.
Published: April 2009

The effectiveness of a thermoelectric device is measured by the figure of merit ZT, which is inversely proportional to the thermal conductivity. Superlattice materials often have a reduced thermal conductivity because of the introduction of interface scattering and, therfore, improved performance. The present work is focused on the effective thermal conductivity of nanocomposite films. This configuration could also improve ZT because of phonon-interface scattering introduced by the nanocrystals. The effects of crystal size and mass fraction is studied numerically using a molecular dynamics simulation. Results indicate that a reduction in the effective thermal conductivity can be achieved with the addition of a nanocrystal.