bluuebunny/crossref_metadata_2025 huggingface dataset:
Increased adhesion of peripheral blood neutrophils from patients with localized juvenile periodontitis
Authors: Hurttia H. , Saarinen K. , Leino L.
Published: June 2010

Adhesion of peripheral blood neutrophils from 5 patients with localized juvenile periodontitis (LJP) and age‐ and gender‐matched healthy controls was measured using a semi‐automated 96‐well microtiter plate assay method. Both unstimulated and formyl‐methionyl‐leucyl‐phenylalanine (FMLP, 10‐1000 nM)‐stimulated neutrophils from LJP patients showed in general higher adhesion than did their controls. After 15‐60 min incubation with 100 and 1000 nM FMLP the numbers of adherent cells were significantly (p<0.05), 2.1‐2.6‐fold higher in LJP patients than in controls. Neutrophils from these LJP patients showed also enhanced respiratory burst activity in response to unopsonized zymosan stimulation. To test whether a decrease in intracellular diacylglycerol (DAG) kinase activity could account for the increased neutrophil adhesion of LJP patients normal neutrophils were treated with R59949 (10 μm), a DAG‐kinase inhibitor. Both unstimulated and FMLP‐stimulated normal neutrophils showed significantly (p<0.05) enhanced adhesion after R59949‐treatment. Taken together, our data indicate that neutrophils from the 5 LJP patients investigated here exhibit 2 parallel hyperactivities, namely increased adhesion and enhanced production of reactive oxygen species. Furthermore, our present and previous (Hurttia et al., J Periodont Res 1997; 32: 401‐407) results suggest that the observed neutrophil functional abnormalities in some LJP patients may be associated with decreased cellular DAG‐kinase activity. It is proposed that the hyperadherent and ‐active neutrophils may promote the development of LJP by causing tissue damage in the periodontium.
Expression of receptors for basic fibroblast growth factor on human periodontal ligament cells
Authors: Takayama S. , Murakami S. , Nozaki T. , Ikezawa K. , Miki Y. , Asano T. , Terashima A. , Okada H.
Published: June 2010

Basic fibroblast growth factor (FGF‐2; bFGF) is a major mitogen for connective tissue cells, and participates in the healing process. It has already been reported that FGF‐2 could be applicable to enhance periodontal regeneration. In the present study, we examined FGF receptor (FGFR) expression on human periodontal ligament (PDL) cells. The binding of [125I]‐labeled FGF‐2 to human PDL cells was studied by radioreceptor assay. The binding of [125I]‐FGF‐2 to PDL cells reached a plateau after 2.5 h incubation at 4°C and was inhibited by the addition of unlabeled FGF‐2 and acidic FGF (FGF‐1; aFGF), but not insulin‐like growth factor‐I, platelet‐derived growth factor and transforming growth factor‐β1. Scatchard analysis revealed the presence of approximately 1.0 × 105 FGF‐2 binding sites per cell with an apparent Kd of 1.2 × 10‐10 M. Interestingly, the binding of [125I]‐FGF‐2 on PDL cells reached its maximum at d 6 of the culture and then gradually decreased. Scatchard analysis also demonstrated that the number of FGFRs on a PDL cell was altered during the course of the culture, while the affinity between FGF‐2 and its receptor was not. The responsiveness of PDL cells to FGF‐2, which was monitored by the inhibitory effect on alkaline phosphatase activity, was reduced in proportion to the decrease in the number of FGFRs on the PDL cells. The present study suggests that PDL cells alter the responsiveness to FGF‐2 during the course of the culture by changing the density of its receptor, and that the density of FGFR expression might be a marker of the cytodiflerentiation of PDL cells into mineralized tissue forming cells.
Differential proliferation of fibroblasts cultured from hereditary gingival fibromatosis and normal gingiva
Authors: Coletta R. D. , Almeida O. P. , Graner E. , Page R. C. , Bozzo L.
Published: June 2010

Hereditary gingival fibromatosis (HGF) is an oral condition characterized by the enlargement of the gingiva of both the maxilla and mandible. To study the cell proliferation index of fibroblasts from HGF and normal gingiva (NG), cell cultures from 4 members of the same family with HGF and from 4 healthy patients were established. Our results obtained from 6 different cell proliferation assays clearly showed that the cell proliferation rate was significantly higher in fibroblasts from HGF than from normal gingiva. HGF and control fibroblasts in subconfluent culture densities were typically spindle, but in saturation density HGF cells were shorter than control cells. These data suggest that the higher proliferative index of HGF fibroblasts possibly has a role in the pathogenesis of gingival outgrowth in HGF patients.
Normalization of periodontal tissues in osteopetrotic mib mutant rats, treated with CSF‐1
Authors: Wojtowicz Andrzej , Yamauchi Mitsuo , Sotowski Rafal , Ostrowski Kazimierz
Published: June 2010

The osteopetrotic mib mutation in rats causes defects in the skeletal bone tissue in young animals. These defects, i.e. slow bone remodelling, changes in both crystallinity and mineral content, are transient and undergo normalization, even without any treatment in 6‐wk‐old animals. Treatment with CSF‐1 (colony stimulating factor‐1) accelerates the normalization process in skeletal bones. The periodontal tissues around the apices of incisors show abnormalities caused by the slow remodelling process of the mandible bone tissue, the deficiency of osteoclasts and their abnormal morphology, as well as the disorganization of periodontal ligament fibres. In contrast to the skeletal tissues, these abnormalities would not undergo spontaneous normalization. Under treatment with colony stimulating factor 1 (CSF‐1), the primitive bone trabeculae of mandible are resorbed and the normalization of the number of osteoclasts and their cytology occurs. The organization of the periodontal ligament fibres is partially restored, resembling the histological structure of the normal one.
Incidence and risk factors of pressure ulcers in seven neonatal intensive care units in Japan: a multisite prospective cohort study
Authors: Fujii Kumiko , Sugama Junko , Okuwa Mayumi , Sanada Hiromi , Mizokami Yuko
Published: June 2010

This study aims to clarify (i) the incidence of pressure ulcers in neonates admitted to the neonatal intensive care units (NICUs) and (ii) risk factors of pressure ulcer development. All infants admitted to the NICU and kept in incubators from seven hospitals during the study period were recruited to the study. Each infant was given skin examination every day by nurses, and risk factors were collected three times a week by one researcher. The incidence of the pressure ulcers was calculated, and the risk factors for pressure ulcers were determined by using univariate and multivariate analysis. Eighty‐one infants were involved in the study. A total of 14 pressure ulcers occurred in 13 infants during the 11‐month study period, the incidence was 0·01 persons per day and cumulative incidence rate was 16·0%. Seven (50·0%) of 14 pressure ulcers were located on the nose. Multivariate analysis identified the following risk factors: skin texture (Dubowitz neonatal maturation assessment scale: skin texture score of 1 point or lower) [odds ratio 7·6; 95% confidence interval (CI) 1·58 –36·71, P = 0·012] and endotracheal intubation usage (odds ratio 4·0; 95% CI 1·04–15·42, P = 0·042).
The effect and safety after extended use of continuous negative pressure of 75 mmHg over mesh and allodermis graft on open sternal wound from oversized heart transplant in a 3‐month‐old infant*
Authors: Lee Kangwoo Nathan , Seo Dong Man , Hong Joon Pio
Published: June 2010

Negative pressure therapy (NPT) has been reported to be effective in treating infants with open chest wounds. This report further supports its effectiveness by treating a 3‐month‐old infant with a 12 × 7 cm sized opening in its chest after an oversized heart transplantation. After applying a mesh and allodermis over the defect, 75‐mmHg continuous negative pressure was set and used for an extended period of 104 days. The haemodynamic status was evaluated during this period. The wound was closed with secondary intention and it healed well after NPT. There was no haemodynamic instability during the treatment course. The extended use of a continuous negative pressure of 75 mmHg over the mesh and alloderm graft was a reliable and safe option to close the massive defect in the chest of a 3‐month‐old infant.
Application of the Levenshtein Distance Metric for the Construction of Longitudinal Data Files
Authors: Doran Harold C. , Van Wamelen Paul B.
Published: June 2010

The analysis of longitudinal data in education is becoming more prevalent given the nature of testing systems constructed for No Child Left Behind Act (NCLB). However, constructing the longitudinal data files remains a significant challenge. Students move into new schools, but in many cases the unique identifiers (ID) that should remain constant for each student change. As a result, different students frequently share the same ID, and merging records for an ID that is erroneously assigned to different students clearly becomes problematic. In small data sets, quality assurance of the merge can proceed through human reviews of the data to ensure all merged records are properly joined. However, in data sets with hundreds of thousands of cases, quality assurance via human review is impossible. While the record linkage literature has many applications in other disciplines, the educational measurement literature lacks details of formal protocols that can be used for quality assurance procedures for longitudinal data files. This article presents an empirical quality assurance procedure that may be used to verify the integrity of the merges performed for longitudinal analysis. We also discuss possible extensions that would permit merges to occur even when unique identifiers are not available.
Conceptualizing the Classroom of Target Students: A Qualitative Investigation of Panelists' Experiences during Standard Setting
Authors: Hein Serge F. , Skaggs Gary
Published: June 2010

Increasingly, research has focused on the cognitive processes associated with various standard‐setting activities. This qualitative study involved an examination of 16 third‐grade reading teachers' experiences with the cognitive task of conceptualizing an entire classroom of hypothetical target students when the single‐passage bookmark method or the yes/no method was used during a one‐day mock panel meeting. Data were collected using in‐depth focus group interviews with eight participants from each of the panel meetings, and a whole‐text analysis revealed three categories. Most participants experienced difficulty in attempting to conceive of an entire classroom of target students. Most of them were ultimately unable to do so and made use of alternative cognitive strategies. More fundamental issues also contributed to the difficulties experienced in attempting to complete the required cognitive task. Implications of the findings for standard setting and for further research are also discussed.
Reflex conditioning: a new strategy for improving motor function after spinal cord injury
Authors: Chen Xiang Yang , Chen Yi , Wang Yu , Thompson Aiko , Carp Jonathan S. , Segal Richard L. , Wolpaw Jonathan R.
Published: June 2010

Spinal reflex conditioning changes reflex size, induces spinal cord plasticity, and modifies locomotion. Appropriate reflex conditioning can improve walking in rats after spinal cord injury (SCI). Reflex conditioning offers a new therapeutic strategy for restoring function in people with SCI. This approach can address the specific deficits of individuals with SCI by targeting specific reflex pathways for increased or decreased responsiveness. In addition, once clinically significant regeneration can be achieved, reflex conditioning could provide a means of reeducating the newly (and probably imperfectly) reconnected spinal cord.
A Requirement for Bid for Induction of Apoptosis by Photodynamic Therapy with a Lysosome‐ but Not a Mitochondrion‐targeted Photosensitizer
Authors: Chiu Song‐mao , Xue Liang‐yan , Lam Minh , Rodriguez Myriam E. , Zhang Ping , Kenney Malcolm E. , Nieminen Anna‐Liisa , Oleinick Nancy L.
Published: June 2010

Photodynamic therapy (PDT) with lysosome‐targeted photosensitizers induces the intrinsic pathway of apoptosis via the cleavage and activation of the BH3‐only protein Bid by proteolytic enzymes released from photodisrupted lysosomes. To investigate the role of Bid in apoptosis induction and the role of damaged lysosomes on cell killing by lysosome‐targeted PDT, we compared the responses of wild type and Bid‐knock‐out murine embryonic fibroblasts toward a mitochondrion/endoplasmic reticulum‐binding photosensitizer, Pc 4, and a lysosome‐targeted sensitizer, Pc 181. Whereas apoptosis and overall cell killing were induced equally well by Pc 4‐PDT in both cell lines, Bid−/− cells were relatively resistant to induction of apoptosis and to overall killing following PDT with Pc 181, particularly at low PDT doses. Thus, Bid is critical for the induction of apoptosis caused by PDT with the lysosome‐specific sensitizers, but dispensable for PDT targeted to other membranes.
Patient Expectations From Implantable Defibrillators to Prevent Death in Heart Failure
Authors: Harris Scott , Tepper David , Ip Randy
Published: June 2010

Abstract.  Background. Indications for implantable cardioverter‐defibrillators (ICDs) in heart failure (HF) are expanding and may include more than 1 million patients. This study examined patient expectations from ICDs for primary prevention of sudden death in HF.

Methods and Results. Study participants (n=105) had an ejection fraction <35% and symptomatic HF without history of ventricular tachycardia/fibrillation or syncope. Participants completed a written survey about perceived ICD benefits, survival expectations, and circumstances under which they might deactivate defibrillation. Mean age was 58 years, mean left ventricular ejection fraction was 21%, 40% had New York Heart Association class III or IV disease, and 65% already had a primary prevention ICD. Most patients anticipated more than 10 years’ survival despite symptomatic HF. Nearly 54% expected an ICD to save ≥50 lives per 100 during 5 years. ICD recipients expressed more confidence that the device would save their own lives compared with those without an ICD (P<.001). Despite understanding the ease of deactivation, 70% of ICD recipients indicated they would keep the ICD on even if dying of cancer, 55% even if having daily shocks, and none would inactivate defibrillation even if experiencing constant dyspnea at rest.

Conclusions. HF patients anticipate long survival, overestimate survival benefits conferred by ICDs, and express reluctance to deactivate their devices even for end‐stage disease.—Stewart GC, Weintraub JR, Pratibhu PP, et al. Patient expectations from implantable defibrillators to prevent death in heart failure. J Card Fail. 2010;16:106–113.
Digoxin Use and Heart Failure Outcomes: Results from the Valsartan Heart Failure Trial (Val‐HeFT)
Authors: Butler Javed , Anand Inder S. , Kuskowski Michael A. , Rector Thomas , Carson Peter , Cohn Jay N. ,   for the Val‐HeFT Investigators
Published: June 2010

Several retrospective studies have raised concerns regarding digoxin therapy in select subgroups of heart failure patients. To assess the impact of digoxin therapy on outcomes in the current era of heart failure therapy, the authors analyzed data representing 5010 patients enrolled in the Valsartan Heart Failure Trial (Val‐HeFT) to examine the relationship of baseline digoxin use and all‐cause mortality, first morbid event, and heart failure hospitalizations. At baseline, 3374 patients (67%) were receiving digoxin therapy and 1636 (33%) were not. Patients receiving digoxin had features of worse heart failure with higher New York Heart Association class and lower blood pressure, ejection fraction, and β‐blocker use (32.1% vs 40.8%). Digoxin use was associated with worse mortality (21.1 vs 15.0%, P<.001), first morbid event (34.6 vs 21.7, P<.001), and HF hospitalization rate (19.1 vs 10.1%, P<.001). After adjustment for baseline group differences including medical therapy and baseline rhythm, patients receiving digoxin remained at a higher risk for all‐cause mortality (hazard ratio [HR], 1.28; 95% confidence interval [CI], 1.05–1.57), first morbid event (HR, 1.35; 95% CI, 1.15–1.59), and heart failure hospitalization (HR, 1.41; 95% CI, 1.12–1.78). These results remained materially unchanged with propensity matched analysis. No benefit with digoxin use was observed in this study, underscoring the need to reassess the role of digoxin in the contemporary management of heart failure. Congest Heart Fail. 2010;16:191–195. © 2010 Wiley Periodicals, Inc.
Lake Temperature and Ice Cover Regimes in the Alaskan Subarctic and Arctic: Integrated Monitoring, Remote Sensing, and Modeling1
Authors: Arp C.D. , Jones B.M. , Whitman M. , Larsen A. , Urban F.E.
Published: June 2010

Arp, C.D., B.M. Jones, M. Whitman, A. Larsen, and F.E. Urban, 2010. Lake Temperature and Ice Cover Regimes in the Alaskan Subarctic and Arctic: Integrated Monitoring, Remote Sensing, and Modeling. Journal of the American Water Resources Association (JAWRA) 46(4): 777‐791. DOI: 10.1111/j.1752‐1688.2010.00451.x

Abstract:  Lake surface regimes are fundamental attributes of lake ecosystems and their interaction with the land and atmosphere. High latitudes may be particularly sensitive to climate change, however, adequate baselines for these lakes are often lacking. In this study, we couple monitoring, remote sensing, and modeling techniques to generate baseline datasets of lake surface temperature and ice cover in the Alaskan Subarctic and Arctic. No detectable trends were observed during this study period, but a number of interesting patterns were noted among lakes and between regions. The largest Arctic lake was relatively unresponsive to air temperature, while the largest Subarctic lake was very responsive likely because it is fed by glacial runoff. Mean late summer water temperatures were higher than air temperatures with differences ranging from 1.7 to 5.4°C in Subarctic lakes and from 2.4 to 3.2°C in Arctic lakes. The warmest mean summer water temperature in both regions was in 2004, with the exception of Subarctic glacially fed lake that was highest in 2005. Ice‐out timing had high coherence within regions and years, typically occurring in late May in Subarctic and in early‐July in Arctic lakes. Ice‐on timing was more dependent on lake size and depth, often varying among lakes within a region. Such analyses provide an important baseline of lake surface regimes at a time when there is increasing interest in high‐latitude water ecosystems and resources during an uncertain climate future.
A review of coronectomy
Authors: Frafjord R. , Renton T.
Published: June 2010

Coronectomy or intentional partial odontectomy is a procedure whereby the root(s) of a lower third molar tooth that is deemed close to the inferior alveolar canal on radiographic imaging is left in‐situ. Coronectomy is a relatively new procedure and to date there have only been a handful of publications that investigate its' effectiveness as a treatment modality. As a result it is still not commonly practiced worldwide. However, coronectomy is gaining popularity as a risk reducing procedure. This article looks at nine most recent studies on coronectomy and reviews each paper with respect to treatment outcomes.
Marlin, software to create, run, and analyse spatially realistic simulations
Authors: MEIRMANS PATRICK G.
Published: June 2010

Marlin is a software to create, run, analyse, and visualize spatially explicit population genetic simulations. It provides an intuitive user interface with which the geographical layout of a metapopulation can be drawn by hand or loaded from a map. Furthermore, the interface allows easy selection of the many different simulation settings. Marlin then uses the program QuantiNemo to run the simulation in the background. When simulations are finished, Marlin directly analyses and plots the results, thereby greatly simplifying the simulation workflow. This combination of simulation and analysis makes Marlin ideal for teaching and for scientists who are interested in doing simulations without having to learn command‐line operations. Marlin is available for computers running Mac OS X and can be downloaded from: http://www.patrickmeirmans.com/software.
REVIEW: Stent Thrombosis—Risk Assessment and Prevention
Authors: Motovska Zuzana , Knot Jiri , Widimsky Petr
Published: June 2010

The development and use of stents has made percutaneous coronary intervention an effective (less restenosis), safe (treatment of emergency vessel closure during balloon angioplasty), and applicable (stents were developed for lesions of tortuous anatomy and complex situations) revascularization method. These features have firmly established stenting as first‐line therapy in coronary revascularization. This life‐saving device carries, however, the risk of a life‐threatening complication—stent thrombosis. The article summarizes the facts about the incidence, histopathology, and risk factors of bare‐metal as well as drug‐eluting stent thrombosis. Future directions in reducing the incidence of stent thrombosis are also outlined.
Seeking Brain Biomarkers for Preventive Therapy in Huntington Disease
Authors: Esmaeilzadeh Mouna , Ciarmiello Andrea , Squitieri Ferdinando
Published: June 2010

Huntington disease (HD) is a severe incurable nervous system disease that generally has an onset age of around 35–50, and is caused by a dominantly transmitted expansion mutation. A genetic test allows persons at risk, i.e., offspring or siblings of affected individuals, to discover their genetic status. Unaffected mutation‐positive subjects will manifest HD sometime during life. Despite major advances in research on pathogenic mechanisms, no studies have yet fully validated preventive therapy or biomarkers for use before the symptoms become clinically manifest. Seeking brain and peripheral biomarkers is a requisite to develop a cure for HD. Changes in the brain can be observed in vivo using methods such as structural magnetic resonance imaging (MRI), diffusion tensor imaging (DTI), functional MRI (fMRI), and positron emission tomography (PET), detecting volumetric changes, microstructural and connectivity alterations, abnormalities in brain activity in response to specific tasks, and abnormalities in metabolism and receptor distribution. Although all these imaging techniques can detect early markers in asymptomatic HD gene carriers for premanifest screening and pharmacological responses to therapeutic interventions no single modality has yet provided and validated an optimal marker probably because this task requires an integrative multimodal imaging approach. In this article, we review the findings from imaging procedures in the attempt to identify potential brain markers, so‐called dry biomarkers, for possible application to further, yet unavailable, neuroprotective preventive therapies for HD manifestations.
U.S. Soft Power and the “China Threat”: Multilevel Analyses
Authors: Machida Satoshi
Published: June 2010

This study investigates the impact of U.S. “soft power” in the international system. Specifically, it examines how American soft power affects individuals' perceptions of the “China threat.” Based on the theoretical model developed by Rousseau (2006), the present research considers how citizens develop their perceptions of China in relation to the United States. Multilevel analyses relying on the Pew Global Attitudes Project 2007 verify the view highlighting the compatibility of these two states in the international system. The analyses find that the diffusion of U.S. soft power in each state significantly reduces the urgency of the China threat. Implications from this study contribute to our understanding of U.S‐China relations in rapidly changing international environments.
Unraveling the Logic of ASEAN's Decision‐Making: Theoretical Analysis and Case Examination
Authors: Chiou Yi‐hung
Published: June 2010

Throughout its history, the Association of Southeast Asian Nations (ASEAN) has based decisions on consensus and consultation, producing a loosely defined, weak regional organization. The results of nonbinding and watered‐down resolutions make substantial progress for ASEAN difficult. This article explores the logic of ASEAN's decision‐making by applying rational choice theory. It argues that the characteristics of ASEAN's decision‐making mechanism allow member states to base their actions on how individual nations perceive their interests to be best served by group resolutions. By constructing a series of hypotheses to pattern ASEAN's decision‐making, this article examines four cases and how players resolved each. The findings suggest that the constraints of group decision‐making and divergent interests between member states play a major role in shaping the effectiveness of resolutions.
The Rationale, Prospects, and Challenges of China's Western Economic Triangle in Light of Global Economic Crisis
Authors: Yu Hong
Published: June 2010

The proposals to develop the Western Economic Triangle (WET) region into the fourth growth pole in China are ambitious; realization will be problematic. Although the local governments are overwhelmingly optimistic regarding future development, it is very unlikely that this region can become as powerful and vibrant as the eastern growth engines in the near future. Implementation of the proposals faces at least two serious challenges. First, the WET region has historically suffered from poor accessibility due to backward interregional transportation facilities. Second, the WET region is governed by three different administrative municipalities. The inherent lack of regional integration and coordination will restrict industrial cooperation within this region.
Innovation, Branding, and Organization: What International Design Managers Think About Their Performance
Authors: Joziasse Frans , Selders Tim , Woudhuysen James
Published: June 2010

Since the dot.com boom and Clayton Christensen's book, The Innovator's Dilemma, there has been an international revival of interest in innovation. At the same time, corporate interest in branding remains buoyant. On a third issue—a world of cost‐cutting, off‐shoring, and IT—millions of managers have been forced to focus on organization. What is unclear is how design managers interpret their tasks in the current climate, and how well they think they are performing these tasks.

PARK, a network of consultants in advanced design management, worked with Wouter Voskuijl, a masters student at the Delft University of Technology, to seek responses from 300 design managers worldwide. Positive and negative correlations were then made between their primary objectives and their experiences.

Broad conclusions were drawn from the survey. These include the persistence of silos and the prevalence of competition within organizations, which lead design managers to feel left in the dark about other internal departments. It is also apparent that design managers feel far removed from corporate strategy. This may explain design management's fascination with measuring its performance to be commendable, which perhaps reflects a level of defensiveness.
In‐House Design: How Do Design Managers Manage Change?
Authors: Gornick Naomi
Published: June 2010

This study examines new directions in design and management theory and practice, and illustrates how design managers in large corporations are responding to organizational change and new contexts for design. The paper will re‐visit design managers who have initially trained as designers and whose career flowed naturally into this field, as well as those design managers who undertook specific post‐graduate training in order to enter the field.

Companies such as BAA, Nokia, and Procter & Gamble are represented in order to provide a picture of the evolutionary changes taking place within these organizations and how the work of design managers is affected.

Interviewees were asked to comment on the changes they have experienced in their companies over a period of several years and comment on the increasing overlap of their work with that of their management colleagues. In conclusion, the paper discusses potential opportunities for new design roles and the advanced education needed to train effectively for those roles.
Criteria for Cross-Plane Dominated Thermal Transport in Multilayer Thin Film Systems During Modulated Laser Heating
Authors: Hopkins Patrick E. , Serrano Justin R. , Phinney Leslie M. , Kearney Sean P. , Grasser Thomas W. , Harris C. Thomas
Published: June 2010

Pump-probe transient thermoreflectance (TTR) techniques are powerful tools for measuring the thermophysical properties of thin films, such as thermal conductivity, Λ, or thermal boundary conductance, G. This paper examines the assumption of one-dimensional heating on, Λ and G, determination in nanostructures using a pump-probe transient thermoreflectance technique. The traditionally used one-dimensional and axially symmetric cylindrical conduction models for thermal transport are reviewed. To test the assumptions of the thermal models, experimental data from Al films on bulk substrates (Si and glass) are taken with the TTR technique. This analysis is extended to thin film multilayer structures. The results show that at 11 MHz modulation frequency, thermal transport is indeed one dimensional. Error among the various models arises due to pulse accumulation and not accounting for residual heating.
Modeling Carrier-Phonon Nonequilibrium Due to Pulsed Laser Interaction With Nanoscale Silicon Films
Authors: Pattamatta Arvind , Madnia Cyrus K.
Published: June 2010

Ultrashort-pulsed laser irradiation on semiconductors creates a thermal nonequilibrium between carriers and phonons. Previous computational studies used the “two-temperature” model and its variants to model this nonequilibrium. However, when the laser pulse duration is smaller than the relaxation time of the carriers or phonons or when the carriers’ or phonons’ mean free path is larger than the material dimension, these macroscopic models fail to capture the physics accurately. In this article, the nonequilibrium between carriers and phonons in silicon films is modeled via numerical solution of the Boltzmann transport model (BTM), which is applicable over a wide range of length and time scales. The BTM is solved using the discontinuous Galerkin finite element method for spatial discretization and the three-stage Runge–Kutta temporal discretization. The BTM results are compared with previous computational studies on laser heating of macroscale silicon films. The model is then used to study laser heating of nanometer size silicon films, by varying parameters such as the laser fluence and pulse duration. From the laser pulse duration study, it is observed that the peak carrier number density, and maximum carrier and phonon temperatures are the highest for the shortest pulse duration of 0.05 ps and decreases with increasing pulse duration. From the laser fluence study, it is observed that for fluences equal to or higher than 1000 J/m2, due to the Auger recombination, a second peak in carrier temperature is observed. The use of carrier-acoustic phonon coupling leads to equilibrium phonon temperatures, which are approximately 400 K higher than that of carrier-optical phonon-acoustic phonon coupling. Both the laser pulse duration and fluence are found to strongly affect the equilibrium time and temperature in Si films.
Analytical Solution for Forced Convection in a Sector Duct Filled With a Porous Medium
Authors: Wang C. Y.
Published: June 2010

The fully developed viscous flow through a sector duct filled with a porous medium is studied. The Darcy–Brinkman and energy equations are solved analytically by series expansions in Bessel functions of the first kind. The problem is governed by a porous medium parameter s, which is proportional to the inverse square root of the permeability. For large s there exists a boundary layer on the walls, and the resistance increases greatly. The Nusselt number for the H1 heat transfer problem also increases. If the apex angle is acute, the local velocity and heat transfer are very low. If the apex angle is obtuse, the local shear and heat transfer are large. Tables for the friction factor-Reynolds number products and Nusselt numbers are determined for various s and apex angles.
Heat Flux Estimation in a Nonlinear Inverse Heat Conduction Problem With Moving Boundary
Authors: Molavi Hosein , Rahmani Ramin K. , Pourshaghaghy Alireza , Tashnizi Ebrahim Sharifi , Hakkaki-Fard Ali
Published: June 2010

The estimation of heat flux in the nonlinear heat conduction problem becomes more challenging when the material at the boundary loses its mass due to phase change, chemical erosion, oxidation, or mechanical removal. In this paper, a new gradient-type method with an adjoint problem is employed to predict the unknown time-varying heat flux at the receding surface in the nonlinear heat conduction problem. Particular features of this novel approach are discussed and examined. Results obtained by the new method for several test cases are benchmarked and analyzed using numerical experiments with simulated exact and noisy measurements. Exceedingly reliable estimation on the heat flux can be obtained from the knowledge of the transient temperature recordings, even in the case with measurement errors. In order to evaluate the performance characteristics of the present inverse scheme, simulations are conducted to analyze the effects of this technique with regard to the conjugate gradient method with an adjoint problem and variable metric method with an adjoint problem. The results obtained show that the present inverse scheme distinguishably accelerates the convergence rate, which approve the well capability of the method for this type of heat conduction problems.
Experimental Investigation of an Ultrathin Manifold Microchannel Heat Sink for Liquid-Cooled Chips
Authors: Escher W. , Brunschwiler T. , Michel B. , Poulikakos D.
Published: June 2010

We report an experimental investigation of a novel, high performance ultrathin manifold microchannel heat sink. The heat sink consists of impinging liquid slot-jets on a structured surface fed with liquid coolant by an overlying two-dimensional manifold. We developed a fabrication and packaging procedure to manufacture prototypes by means of standard microprocessing. A closed fluid loop for precise hydrodynamic and thermal characterization of six different test vehicles was built. We studied the influence of the number of manifold systems, the width of the heat transfer microchannels, the volumetric flow rate, and the pumping power on the hydrodynamic and thermal performance of the heat sink. A design with 12.5 manifold systems and 25 μm wide microchannels as the heat transfer structure provided the optimum choice of design parameters. For a volumetric flow rate of 1.3 l/min we demonstrated a total thermal resistance between the maximum heater temperature and fluid inlet temperature of 0.09 cm2 K/W with a pressure drop of 0.22 bar on a 2×2 cm2 chip. This allows for cooling power densities of more than 700 W/cm2 for a maximum temperature difference between the chip and the fluid inlet of 65 K. The total height of the heat sink did not exceed 2 mm, and includes a 500 μm thick thermal test chip structured by 300 μm deep microchannels for heat transfer. Furthermore, we discuss the influence of elevated fluid inlet temperatures, allowing possible reuse of the thermal energy, and demonstrate an enhancement of the heat sink cooling efficiency of more than 40% for a temperature rise of 50 K.
Multi-Objective Optimization of Heat Exchanger Design by Entropy Generation Minimization
Authors: Guo Jiangfeng , Cheng Lin , Xu Mingtian
Published: June 2010

In the present work, a multi-objective optimization of heat exchanger thermal design in the framework of the entropy generation minimization is presented. The objectives are to minimize the dimensionless entropy generation rates related to the heat conduction under finite temperature difference and fluid friction under finite pressure drop. Constraints are specified by the admissible pressure drop and design standards. The genetic algorithm is employed to search the Pareto optimal set of the multi-objective optimization problem. It is found that the solutions in the Pareto optimal set are trade-off between the pumping power and heat exchanger effectiveness. In some sense, the optimal solution in the Pareto optimal set achieves the largest exchanger effectiveness by consuming the least pumping power under the design requirements and standards. In comparison with the single-objective optimization design, the multi-objective optimization design leads to the significant decrease in the pumping power for achieving the same heat exchanger effectiveness and presents more flexibility in the design process.
System Evaluation and Economic Analysis of a Nuclear Reactor Powered High-Temperature Electrolysis Hydrogen-Production Plant
Authors: Harvego E. A. , McKellar M. G. , Sohal M. S. , O’Brien J. E. , Herring J. S.
Published: June 2010

A reference design for a commercial-scale high-temperature electrolysis (HTE) plant for hydrogen production was developed to provide a basis for comparing the HTE concept with other hydrogen-production concepts. The reference plant design is driven by a high-temperature helium-cooled nuclear reactor coupled to a direct Brayton power cycle. The reference design reactor power is 600 MWt, with a primary system pressure of 7.0 MPa, and reactor inlet and outlet fluid temperatures of 540°C and 900°C, respectively. The electrolysis unit used to produce hydrogen includes 4,009,177 cells with a per-cell active area of 225 cm2. The optimized design for the reference hydrogen-production plant operates at a system pressure of 5.0 MPa, and utilizes an air-sweep system to remove the excess oxygen that has evolved on the anode (oxygen) side of the electrolyzer. The inlet air for the air-sweep system is compressed to the system operating pressure of 5.0 MPa in a four-stage compressor with intercooling. The alternating current to direct current conversion efficiency is 96%. The overall system thermal-to-hydrogen-production efficiency (based on the lower heating value of the produced hydrogen) is 47.1% at a hydrogen-production rate of 2.356 kg/s. This hydrogen-production efficiency is considerably higher than can be achieved using current low-temperature electrolysis techniques. An economic analysis of this plant was performed using the standardized hydrogen analysis methodology developed by the Department of Energy Hydrogen Program, and using realistic financial and cost estimating assumptions. The results of the economic analysis demonstrated that the HTE hydrogen-production plant driven by a high-temperature helium-cooled nuclear power plant can deliver hydrogen at a competitive cost. A cost of $3.23/kg of hydrogen was calculated assuming an internal rate of return of 10%.
Fluid Flow and Heat Transfer in a Horizontal Channel With Divergent Top Wall and Heated From Below
Authors: Yang C. S. , Jeng D. Z. , Liu C. W. , Liu C. G. , Gau C.
Published: June 2010

Secondary flow structure and its enhancement on the heat transfer in a horizontal divergent channel have been studied. The bottom wall is horizontal and is heated uniformly while the opposite top wall is insulated and inclined with respect to the horizontal plane so as to create a divergent angle of 3 deg. At the entrance of the channel, the aspect ratios for the width to the height and the channel length to the height are 6.67 and 15, respectively. The Reynolds number ranges from 100 to 2000 and the buoyancy parameter Gr/Re2 from 0 to 405. Both flow visualization and temperature fluctuation measurements at different locations are made to indicate the flow structure and oscillation of the secondary flow. The adverse pressure gradient in the divergent channel causes a thicker heated layer in the bottom and earlier initiation of secondary flow. Interaction between neighboring vortices and plumes becomes more severe and highly unstable. This precludes the formation of steady two-dimensional longitudinal vortex rolls in the downstream and leads to an earlier and larger enhancement of the heat transfer than the case of the parallel-plate channel. The effects of the buoyancy parameter and the divergence of the channel on the secondary flow structure and the Nusselt number are presented and discussed.
A Geometrically Exact Rod Model Including In-Plane Cross-Sectional Deformation
Authors: Kumar Ajeet , Mukherjee Subrata
Published: June 2010

We present a novel approach for nonlinear, three dimensional deformation of a rod that allows in-plane cross-sectional deformation. The approach is based on the concept of multiplicative decomposition, i.e., the deformation of a rod’s cross section is performed in two steps: pure in-plane cross-sectional deformation followed by its rigid motion. This decomposition, in turn, allows straightforward extension of the special Cosserat theory of rods (having rigid cross section) to a new theory allowing in-plane cross-sectional deformation. We then derive a complete set of static equilibrium equations along with the boundary conditions necessary for analytical/numerical solution of the aforementioned deformation problem. A variational approach to solve the relevant boundary value problem is also presented. Later we use symmetry arguments to derive invariants of the objective strain measures for transversely isotropic rods, as well as for rods with inbuilt handedness (hemitropy) such as DNA and carbon nanotubes. The invariants derived put restrictions on the form of the strain energy density leading to a simplified form of quadratic strain energy density that exhibits some interesting physically relevant coupling between the different modes of deformation.
Flame Stretching in a Room Model With Natural Vent
Authors: Chow W. K. , Han S. S. , Gao Y. , Dong H. , Huo Y. , Zhang Y. M. , Li S. S.
Published: June 2010

Flame stretching in a room with a ceiling vent will be discussed in this short note. A real-scale model was constructed with a gasoline pool fire placed inside. Another pool fire of the same size and amount of fuel was burnt outside the model. Different pool sizes of diameters 0.07 m, 0.08 m, 0.11 m, 0.16 m and 0.2 m were set up. Volume of gasoline varied from 30 ml to 500 ml to give different burning durations. The flame lengths of the two fires were measured and compared. It is observed that the flame length of the pool fire inside the room was over 20% higher than that outside at the later stage of the fire.
Experimental Investigation on Heat Transfer of CO2 Solid-Gas Two Phase Flow With Dry Ice Sublimation
Authors: Zhang Xin-Rong , Yamaguchi Hiroshi
Published: June 2010

From the viewpoint of protecting the ozone layer and preventing global warming, there is now strong demand for science and technology based on ecologically safe ‘natural’ working fluids. A CO2 refrigeration method has been proposed and developed several years ago, using CO2 solid-gas two phase fluid as refrigerant. Heat transfer of the CO2 solid-gas two phase flow in a horizontal tube is important to design of such a refrigeration system. In the present paper, an experiment work is conducted to measure its heat transfer characteristics in the horizontal tube. The results show an average value 310 W/(m2-K) of heat convective coefficient is experimentally obtained, which is much higher than that of gas flow. In the sublimation area, the Nusselt number is observed to increase slowly along the tube length, the phenomena may be physically explained that the sublimation process changes the thermal boundary layer thickness; makes the flow turbulence stronger; or changes the flow and the pressure fields.
Investigation of Phonon Scattering and Thermal Conductivity Reduction in Thermoelectric Materials Using Ultrafast Time-Resolved Optical Measurements
Authors: Wang Yaguo , Xu Xianfan
Published: June 2010

Upon filling, caged compounds like skutterudites can have their lattice thermal conductivity reduced by 4∼5 times compared with unfilled structures [1]. Recently, it was found that the thermal conductivity in Bi2Te3/Sb2Te3 superlattice structure is also greatly reduced, even comparing with its corresponding alloy, in the cross-plane direction [2]. A fundamental understanding of thermal conductivity reduction in these structures is important due to their enhanced thermoelectric figure of merit. For filled skutterudites, “phonon-glass-electron-crystal (PGEC)” scheme was adopted to describe the role of guest atoms in the cages constructed by host atoms [3]. The localized and incoherent “rattling” behavior of guest atoms cuts down the mean free path of phonons, which results in reduced lattice thermal conductivity. In this study we apply ultrafast time resolved measurement technique to study coherent phonons in Bi2Te3/Sb2Te3 superlattice and coherent vibrations in misch metal filled skutterudites, aim to reveal the mechanisms behind thermal conductivity reduction.
Quantification of Heat Flux From a Reacting Thermite Spray
Authors: Nixon Eric , Pantoya Michelle , Prentice Daniel
Published: June 2010

Characterizing the combustion behaviors of energetic materials requires diagnostic tools that are often not readily or commercially available. For example, a jet of thermite spray provides a high temperature and pressure reaction that can also be highly corrosive and promote undesirable conditions for the survivability of any sensor. Developing a diagnostic to quantify heat flux from a thermite spray is the objective of this study. Quick response sensors such as thin film heat flux sensors can not survive the harsh conditions of the spray, but more rugged sensors lack the response time for the resolution desired. A sensor that will allow for adequate response time while surviving the entire test duration was constructed. The sensor outputs interior temperatures of the probes at known locations and utilizes an inverse heat conduction code to calculate heat flux values. The details of this device are discussed and illustrated. Temperature and heat flux measurements of various thermite spray conditions are reported. Results indicate that this newly developed energetic material heat flux sensor provides quantitative data with good repeatability.
Random Surface Roughness Effect on Microtube Heat Transfer
Authors: Xiong Renqiang
Published: June 2010

We propose a novel bottom-up approach to generate a rough microtube surface. This approach starts from four corner points with two defined coordinates and roughness height created by a Gaussian number generator, and uses a bi-cubic Coons patch repeatedly to form the curved surface. A computational fluid dynamics solver is used to isolate the roughness effect and solve the three-dimensional N-S equations for the flow through the generated rough microtubes with diameter D = 50μm and length L = 100μm. The boundary conditions are carefully defined for results comparison between smooth and rough microtubes. It is found that when the mean diameter of the rough microtube is used as the hydraulic diameter, the roughness has little effect on the averaged Nusselt number and it still can be predicted by the conventional theory because the effects of peaks and valleys are counteracted for the whole microtube. The local Nusselt numbers along the microtube randomly distribute below the theoretical value with a very small deviation.