bluuebunny/crossref_metadata_2025 huggingface dataset:
Clinical experiences derived from implementation of an easy to use concept for treatment of wound healing by secondary intention and guidance in selection of appropriate dressings
Authors: Braumann Chris , Guenther Nina , Menenakos Charalambos , Muenzberg Helga , Pirlich Matthias , Lochs Herbert , Mueller Joachim M
Published: March 2011

The main objective of this case‐cohort‐type observational study conducted at different Surgical Departments of the Charité‐Universitätsmedizin in Berlin was to evaluate the sequential use concept first described by Systagenix Wound Management in 2007. Fifty‐two patients with different wound healing by secondary intention were treated for 7 weeks at the Charité‐Universitätsmedizin in Berlin. A multidisciplinary team worked together to reach consensus in wound assessment; in classification of infection status according to the criteria described by European Wound Management Association (EWMA); in treatment protocol and on dressings to be used to ‘cover’ wounds. Before dressing application, all wounds were cleaned from debris. Following the sequential use concept, wounds classified as stages 2 and 3 were dressed with SILVERCEL® and TIELLE® or TIELLE PLUS® to ‘clean’ the wounds. After 2–3 weeks, treatment was changed to PROMOGRAN PRISMA® and TIELLE® to ‘close and cover’ wounds, thus providing optimal wound healing. Wounds classified as non infected were dressed with PROMOGRAN PRISMA® and TIELLE® during the complete treatment period. Patients were asked to evaluate the treatment using a simplified questionnaire developed at the Charité‐Universitätsmedizin in Berlin. Wounds comprised 37 surgical procedures, 8 chronic mixed ulcer, 4 pressure sores, 1 diabetic foot ulcer, 1 venous leg ulcer, and 1 mixed arterial/venous ulcer. At baseline, 12 wounds were classified as stage 3, 38 wounds as stage 2 and 2 wounds as stage 1. After 7 weeks of treatment, all patients showed a positive clinical response to the sequential use treatment. Results of wound size showed a high significant progression of wound healing expressed with a profound reduction of wound area (P in all measurements <0·001, chi‐square test) and improved granulation. This study summarises the clinical experiences derived from the evaluation of the sequential use concept in the daily clinical practice of wound treatment. On the basis of the wound healing results, patients' evaluation of treatment and the clinicians' and staff experiences, this concept was implemented at different Surgical Departments of the Charité‐Universitätsmedizin in Berlin.
Have baryonic acoustic oscillations in the galaxy distribution really been measured?
Authors: Cabré Anna , Gaztañaga Enrique
Published: March 2011

Recent publications claim that there is no convincing evidence for measurements of the baryonic acoustic oscillation (BAO) feature in galaxy samples using either monopole or radial information. Different claims seem contradictory: data are either not consistent with the BAO model or data are consistent with both the BAO model and featureless models without BAO. We investigate this point with a set of 216 realistic mock galaxy catalogues extracted from MICE 7680, one of the largest volume dark matter simulation run to date, with a volume of 1300 cubical gigaparsecs. Our mocks cover similar volume, densities and bias as the real galaxies and provide 216 realizations of the lambda or ω=−1 cold dark matter (ωCDM) BAO model. We find that only 20 per cent of the mocks show a statistically significant (3σ) preference for the true (input) ωCDM BAO model as compared to a featureless (non-physical) model without BAO. Thus the volume of current galaxy samples is not yet large enough to claim that the BAO feature has been detected. Does this mean that we cannot locate the BAO position? Using a simple (non-optimal) algorithm we show that in 50 per cent (100 per cent) of the mocks, we can find the BAO position within 5 per cent (20 per cent) of the true value. These two findings are not in contradiction: the former is about model selection and the later is about parameter fitting within a model. We conclude that current monopole and radial BAO measurements can be used as standard rulers if we assume ωCDM type of models.
The phenotypic and genetic assessment of antithrombin deficiency
Authors: COOPER P. C. , COATH F. , DALY M. E. , MAKRIS M.
Published: March 2011

Introduction:  Antithrombin (AT) deficiency is associated with an increased risk of deep vein thrombosis and pulmonary embolism which are major causes of morbidity and death. The incidence of deficiency in healthy populations has been reported to vary from 1/600 to 1/5 000, with the variation being due to the different populations studied and detection methods used. When reduced activity levels are identified it is important to measure the AT antigen levels to differentiate type I from type II disorders, as type II defects have varying thrombotic risk.

Methods:  Functional AT assays detect the ability of AT to inactivate thrombin or factor Xa, and AT antigen assays detect the quantity of AT in plasma. In functional assays, reducing the incubation time of sample with enzyme/heparin reagent may increase sensitivity to type II defects. An excess of antigen over activity level suggests the presence of functionally defective AT, which can be characterized further by assaying AT in the absence of heparin, electrophoresis to investigate the ability of heparin to bind to AT, and gene sequencing.

Results:  Many patients with AT deficiency have a type II defect and these defects may not be detected by all routine diagnostic assays. Assays using human thrombin may lack specificity and assays that use factor Xa may fail to detect the common variant, AT Cambridge II, which can be detected by assays using bovine thrombin, especially if activity is compared to antigen by ratio. Factor Xa based assays may be particularly sensitive to certain heparin binding defects, and sensitivity of assays to both heparin binding and reactive site defects can be improved by shortening the incubation time with enzyme.

Conclusion:  AT activity assays are essential for the detection of AT deficiency because type II defects are relatively common in patients with heritable deficiency. No one functional assay can be assumed to detect all forms of AT deficiency, and assays can sometimes be improved by reducing reaction time of AT with thrombin or factor Xa.
Effects of Beta‐Blockade on Exercise Performance at High Altitude: A Randomized, Placebo‐Controlled Trial Comparing the Efficacy of Nebivolol versus Carvedilol in Healthy Subjects
Authors: Valentini Mariaconsuelo , Revera Miriam , Bilo Grzegorz , Caldara Gianluca , Savia Giulio , Styczkiewicz Katarzyna , Parati Sara , Gregorini Francesca , Faini Andrea , Branzi Giovanna , Malfatto Gabriella , Magrì Damiano , Agostoni Piergiuseppe , Parati Gianfranco
Published: March 2011

Aims

Exposure to high altitude (HA) hypoxia decreases exercise performance in healthy subjects. Although β‐blockers are known to affect exercise capacity in normoxia, no data are available comparing selective and nonselective β‐adrenergic blockade on exercise performance in healthy subjects acutely exposed to HA hypoxia. We compared the impact of nebivolol and carvedilol on exercise capacity in healthy subjects acutely exposed to HA hypobaric hypoxia.

Methods

In this double‐blind, placebo‐controlled trial, 27 healthy untrained sea‐level (SL) residents (15 males, age 38.3 ± 12.8 years) were randomized to placebo (n = 9), carvedilol 25 mg b.i.d. (n = 9), or nebivolol 5 mg o.d. (n = 9). Primary endpoints were measures of exercise performance evaluated by cardiopulmonary exercise testing at sea level without treatment, and after at least 3 weeks of treatment, both at SL and shortly after arrival at HA (4559 m).

Results

HA hypoxia significantly decreased resting and peak oxygen saturation, peak workload, VO2, and heart rate (HR) (P < 0.01). Changes from SL (no treatment) differed among treatments: (1) peak VO2 was better preserved with nebivolol (–22.5%) than with carvedilol (–37.6%) (P < 0.01); (2) peak HR decreased with carvedilol (–43.9 ± 11.9 beats/min) more than with nebivolol (–24.8 ± 13.6 beats/min) (P < 0.05); (3) peak minute ventilation (VE) decreased with carvedilol (–9.3%) and increased with nebivolol (+15.2%) (P= 0.053). Only peak VE changes independently predicted changes in peak VO2 at multivariate analysis (R= 0.62, P < 0.01).

Conclusions

Exercise performance is better preserved with nebivolol than with carvedilol under acute exposure to HA hypoxia in healthy subjects.
Newsvendor Pricing Problem in a Two‐Sided Market
Authors: Chou Mabel C. , Sim Chee Khian , Teo Chung‐Piaw , Zheng Huan
Published: March 2011

We study the pricing problem of a “platform” intermediary to jointly determine the selling price of the platforms (hardware) sold to consumers and the royalty charged to content developers for content (software), when the demands for content and for platforms are interdependent. Our model elucidates the impact of supply chain replenishment costs and demand uncertainty on the strategic issues of platform pricing in a two‐sided market.
How Provider Selection and Management Contribute to Successful Innovation Outsourcing: An Empirical Study at Siemens
Authors: Cui Zhijian , Loch Christoph , Grossmann Bernd , He Ru
Published: March 2011

It is becoming increasingly common to involve external technology providers in developing new technologies and new products. Two important phases involved in working with technology vendors are vendor selection and vendor management. Because for both steps theory development of key decision guidelines is still immature, we use detailed case studies of 31 innovation outsourcing projects at Siemens to develop grounded theory on provider selection criteria and on project management success drivers. A selection criterion often associated with successful outsourcing is the provider's “track record” or previous experience. Our cases suggest that there is no standard “track record” for success but that a “match” between the client firm's outsourcing motivation and the provider's strengths appears to be a necessary condition for a successful outsourcing collaboration. As to the second phase—managing the vendor—we identify a number of operational project success drivers. There seems to be no universal checklist, but the most important drivers seem to be contingent on the type of vendor chosen and on the maturity of the technology. We compare five provider types—universities, competitors, customers, start‐up companies, and component suppliers—and find that some success drivers are common to all providers, while others are relevant only for certain types of provider. Moreover, drivers in the case of a mature technology are more focused on successful transfer to manufacturing than on development itself. Our findings offer guidelines for innovation managers on how to select innovation providers and how to manage them during the project.
Correlation between clinical and histopathological diagnoses in periapical inflammatory lesions
Authors: Diegues Liliane Lopes , Colombo Robazza Carlos Roberto , Costa Hanemann João Adolfo , Costa Pereira Alessandro Antônio , Silva Cléverson O.
Published: March 2011

Aim:  The purpose of the present study was to evaluate the correlation between clinical and histopathological diagnoses of periapical inflammatory lesions, focusing mainly on cystic conditions.

Methods:  Files dating from 1998 to 2006 at the Oral Pathology Laboratory, School of Dentistry, Alfenas Federal University, Brazil, were reviewed to identify cases with histopathological diagnoses of periapical inflammatory lesions. A total of 1788 files were analyzed, and 255 cases were identified with clinical diagnoses of periapical inflammatory lesions.

Results:  The most prevalent clinical diagnosis was apical periodontal cyst (59%), followed by periapical granuloma (20%), and dentoalveolar abscess (2%). After histopathological analysis, 53% of the cases represented apical periodontal cyst, 42% periapical granuloma, and 5% dentoalveolar abscess.

Conclusions:  The outcomes of the present study show a high prevalence of periapical cysts among periapical inflammatory lesions. Moreover, this study highlights the importance of histopathological evaluation for the correct diagnosis of periapical inflammatory lesions.
Current concepts on gingival fibromatosis‐related syndromes
Authors: Poulopoulos Athanasios , Kittas Dimitrios , Sarigelou Asimina
Published: March 2011

Gingival fibromatosis is a rare, benign, slowly‐growing fibrous overgrowth of the gingiva, with great genetic and clinical heterogeneity. Gingival fibromatosis/overgrowth can be inherited as an isolated trait (hereditary gingival fibromatosis) and/or as a component of a syndrome, or it can be drug induced. As a clinical manifestation of a syndrome, gingival fibromatosis is usually associated with generalized hypertrichosis, mental retardation, or epilepsy. Gingival fibromatosis and its related syndromes are mainly inherited in an autosomal‐dominant manner, but autosomal‐recessive inheritance has also been reported. Clinical syndromic presentation includes Zimmermann–Laband syndrome, Ramon syndrome, Rutherford syndrome, Cowden syndrome, Cross syndrome, Göhlich–Ratmann syndrome, Avani syndrome, and I‐cell disease. However, a phenotypic overlap has been suggested, as many combinations of their systemic manifestations have been reported. Treatment of choice is usually gingivectomy with gingivoplasty. Before any therapy, clinical practitioners must take into consideration the clinical course of a particular syndrome and every possible functional and esthetic disorder.
Dynamic mobilisation exercises increase cross sectional area ofmusculus multifidus
Authors: STUBBS N. C. , KAISER L. J. , HAUPTMAN J. , CLAYTON H. M.
Published: March 2011

Reason for performing study:In human subjects with back pain, the deep spinal stabiliserm. multifidusis inhibited ipsilaterally leading to atrophy, asymmetry and intervertebral instability. Specific physiotherapeutic exercises are required to reactivatem. multifidus. This study assesses the effect of dynamic mobilisation exercises on size and symmetry ofm. multifidusin the equine caudal thoracic and lumbar spine.

Hypotheses:Regular performance of dynamic mobilisation exercises over a period of 3 months increases cross sectional area (CSA) and left‐right symmetry ofm. multifidusmuscles in the caudal thoracic and lumbar spine.

Methods:Eight horses performed dynamic mobilisation exercises (3 cervical flexions, one cervical extension and 3 lateral bending exercises to the left and right sides) with 5 repetitions/exercise/day on 5 days/week for 3 months during which time they were not ridden. Left and rightm. multifidusCSA was measured ultrasonographically at 6 levels from T10 to L5 at the start (initial evaluation) and end (final evaluation) of the 3 month study. Changes in CSA of the right and leftm. multifidusmuscles and symmetry ofm. multifidusCSA on the right and left sides between the 2 evaluations were sought using analysis of variance (P<0.05).

Results:Between the initial evaluation and final evaluationm. multifidusCSA increased significantly at all 6 spinal levels on both right and left sides. Asymmetries inm. multifidusCSA between the right and left sides decreased between the initial and final evaluations.

Conclusions:Hypertrophy of multifidus occurred over a 3 month period during which dynamic mobilisation exercises were the only exercise performed.

Potential relevance:Dynamic mobilisation exercises maybe a useful rehabilitative technique for horses in whichm. multifidushas atrophied in response to back pain.
Nuclear magnetic resonance‐based metabonomic study of early time point laminitis in an oligofructose‐overload model
Authors: KELLER M. D. , POLLITT C. C. , MARX U. C.
Published: March 2011

Reasons for performing study: NMR‐metabonomics is an unbiased evaluation method, which allows to comprehensively study changes of the equine metabolic profile in early time point laminitis. This might give insight into the early stages of disease development.

Objectives: To detect hitherto unknown changes in blood metabolites during the development of oligofructose‐induced laminitis by comparing pre‐ and post induction blood samples.

Methods: Prior to laminitis induction blood was sampled to establish control values. Post oligofructose administration (POA) blood was collected every 3 h for 24 h. One‐dimensional 1H‐NMR spectra of the blood plasma were statistically analysed.

Results: NMR resonances of >20 metabolites were identified using this technique. Already known changes (e.g. lactate concentrations) were confirmed using this method. Interestingly, oligofructose, a carbohydrate usually considered indigestible in the small intestine, or derivatives of oligofructose, was detected in plasma. Horses also showed increased phosphatidylcholine and/or low density lipoprotein levels POA, indicating a change in blood lipid composition. An increase in phosphatidylcholine is consistent with the breakdown of the mucosal layer of the large intestine and increased permeability of the gut.

Conclusion: Due to the nontargeted approach of metabonomics, new unexpected changes can be identified, in this case the hitherto unknown oligofructose uptake through the mucosal wall and the phospholipid changes.

Potential relevance: Metabolic changes in disease can be observed using NMR metabonomics. Oligofructose is used in feedstuffs and transport mechanisms through the mucosa should be studied. Phospholipids could point to a compromise of the intestinal wall during laminitis development.
Assessment of sotalol prescribing in a community hospital: opportunities for clinical pharmacist involvement
Authors: Finks Shannon W , Rogers Kelly C , Manguso Amy H
Published: March 2011

Objective

Due to risk of serious adverse drug events (ADEs) sotalol use is limited in renal insufficiency and heart failure. To reduce potential life-threatening ADEs, medication safety initiatives that ensure appropriate dosing of sotalol are necessary. Pharmacist-managed renal dosing assessment programmes ensure appropriate dosing of renally eliminated medications. A prospective medication safety evaluation was conducted to assess the need to include sotalol in an existing renal dosing assessment programme as well as the impact of clinical pharmacist assessment on sotalol prescribing.

Methods

Patients in a 736-bed community hospital, receiving sotalol during a 6-week period, were prospectively evaluated. Information was collected on indication, dosing, concomitant disease states and medications, renal function, QTc length, symptoms of toxicity and readmissions. Pharmacist recommendations were made when necessary and were followed to determine acceptance rate and patient outcomes.

Key findings

Thirty-six patients were prescribed sotalol for atrial tachyarrhythmias. Thirty-two (89%) were dosed inappropriately with respect to renal function. Twenty (56%) had left-ventricular dysfunction as defined by an ejection fraction of ≤40%. At time of initial assessment, 15 (42%) were exhibiting signs of potential sotalol toxicity. Pharmacists provided recommendations regarding discontinuation or dosage adjustment on 32 patients with a 38% full and a 12% partial acceptance rate. All-cause readmission rates for patients receiving appropriate therapy, including those after pharmacist recommendations were accepted (Group A; n = 16), were compared to those remaining on inappropriate therapy (Group B; n = 20). Readmission rates within 6 months differed between groups (31% for Group A, 55% for Group B; P = 0.095, odds ratio 3.7).

Conclusion

This medication safety evaluation suggests the need for pharmacist assessment in patients receiving sotalol. Dosage adjustment or avoidance in patients with renal insufficiency, heart failure and other relative contraindications is often necessary to avoid toxicity. Sotalol was inappropriately prescribed in the majority of patients secondary to renal insufficiency. Based on this evaluation, it was recommended to add sotalol to the institution's pharmacist-managed renal dosing adjustment programme. Ensuring clinical pharmacist assessment when sotalol is prescribed can help reduce potential life-threatening ADEs and hospital readmissions.
Can I help you? A qualitative study of pharmacist and pharmacy assistant views on the role of pharmacy assistants in New Zealand
Authors: Sheridan Janie , Kelly Fiona , Basheer Mariam , Jan Reem , Lee Alice
Published: March 2011

Objectives

To begin to explore the role of PAs more fully in a New Zealand context, through semi-structured interviews with PAs and pharmacists.

Methods

Semi-structured, qualitative interviews with a convenience sample of pairs of PAs and pharmacists working in a pharmacy together.

Key findings

Pharmacists and PAs both described important roles for PAs. The PAs tended to see themselves as the first point of contact for customers, and that they fulfilled an important healthcare role for the public. Pharmacists agreed that they were the first point of contact yet viewed this more as a gatekeeper role to the pharmacist. Views were also expressed about the difference between PAs and other retail employees. Pharmacists and PAs noted that the ‘public’ expected PAs to have a basic knowledge of non-prescription medicines and their uses. PAs described difficulties when requesting personal information from customers or asking essential questions where the customer had made a specific product request. Being able to know when to refer to the pharmacist was seen as a key role.

Conclusion

Despite being able to describe a number of roles for PAs, these were highly variable. The lack of mandatory training and a clearly articulated role for PAs in New Zealand meant that in some cases PAs might be seen as little more than general retail assistants – a view not in line with their actual roles and practices. Attention to these issues may well help to resolve this, as will public education about the PA's role.
Social change as an important goal or likely outcome: How regulatory focus affects commitment to collective action
Authors: Zaal Maarten P. , Van Laar Colette , Ståhl Tomas , Ellemers Naomi , Derks Belle
Published: March 2011

The results of three experiments showed that regulatory focus influences the way in which the importance and likelihood of social change affect individuals’ commitment to collective action. In Studies 1 (N= 82) and 2 (N= 153), the strength of participants’ chronic regulatory focus was measured. In Study 3 (N= 52), promotion or prevention focus was experimentally induced. The results showed that for individuals under promotion focus, commitment to collective action depended on the perceived likelihood that through this action important social change would be achieved. Individuals under prevention focus were willing to commit to collective action when they attached high importance to its goal, regardless of the extent to which they believed that attainment of this goal was likely. Implications of these results for work on regulatory focus and collective action are discussed.
Single‐unit muscle sympathetic nervous activity and its relation to cardiac noradrenaline spillover
Authors: Lambert Elisabeth A. , Schlaich Markus P. , Dawood Tye , Sari Carolina , Chopra Reena , Barton David A. , Kaye David M. , Elam Mikael , Esler Murray D. , Lambert Gavin W.
Published: March 2011

Non‐technical summary  Recent work has demonstrated differences in the firing pattern of sympathetic nerves in a variety of patient groups. The significance or consequences of this firing pattern remain unknown. We examined whether the nerve firing pattern was associated with increased noradrenaline release from the heart. The activity and pattern of the nerve firing was recorded in the peroneal nerve and subjects were divided into two groups according to the firing pattern as ‘low firing rate’ or ‘high firing rate’. In those with a high firing rate, the noradrenaline released by the heart was two times higher than that of subjects with a low firing rate. This study indicates that the nerve firing pattern may dictate the amount of noradrenaline released by the heart.
Performance Analysis of a Novel Compact Flotation Unit
Authors: Hayatdavoudi A. , Howdeshell M. , Godeaux E. , Pednekar N. , Dhumal V.
Published: March 2011

The oil and gas industry produces large quantities of water as a by-product of petroleum production. Discharge specification of produced water requires efficient management and sophisticated technology. Conventional technologies such as those based on gravity separation, cyclonic separation method, filtration techniques, flotation technique, and natural gas/air sparge tube systems are used for treating produced water. However, most, if not all, of these technologies require a large footprint. This problem has created a challenge for the produced water industry, as well as for operators managing the offshore production facilities. Responding to the challenge at hand, Siemens Water Technologies Corporation has developed a novel compact flotation unit (CFU) equipped with a dissolved gas flotation (DGF) pump for treating produced water. The CFU has a small foot print and shorter residence time. The DGF pump is equipped with a unique, dual-sided impeller, which pulls the blanket gas on one side and the produced water on the other. Under applied backpressure, the gas entering the DGF pump dissolves in a portion of a recycled, cleaned water stream. The dissolved gas generates bubbles due to the pressure drop when the mixture of produced water and gas passes through a special valve before entering the CFU. The ratio of the inlet produced water flow rate to the DGF pump output rate plays an important role in optimum separation of oil droplets from the produced water. Besides the above-mentioned ratio, generation of an adequate number and size of bubbles provides another critical key factor in efficient operation of the CFU system. To validate our theoretical approach regarding the controlled forced vortex of the multiphase flow, we performed various tests in the shop facility of Siemens Water Technologies Corporation, as well as on a platform facility offshore Louisiana. We used a response surface methodology technique to analyze the CFU performance data and to generate an optimum surface response for free oil and grease removal efficiency. For optimizing the size of the piping and CFU dimensions, we used the rigorous yet simple principles of the constrained similitude. The free oil removal efficiency results in the shop and field tests, for CFU without the use of packing material, were satisfactory. Additionally, we found that CFU system tests resulted in the removal efficiency of water soluble oil (WSO). We did not expect this additional outcome as the CFU system was not designed to affect the removal of WSO.
An Experimental Study on Robustness and Process Capability of the Warm Hydroforming Process
Authors: Koç Muammer , Agcayazi Ali , Carsley John
Published: March 2011

The warm sheet hydroforming process was investigated to determine the optimal process conditions of temperature, pressure, and pressurization rate for maximum formability of AA5754-O using an experimental stretch forming die shape. The optimal process conditions were evaluated to determine the robustness and process capability based on physical measurement of formed parts including thickness strain, cavity fill ratio, and radius of curvature. For the simple die shape investigated, a temperature of 268°C, a pressure of 25 MPa, and a pressurization rate of 0.22 MPa/s provided the most balanced combination of uniform thickness strain with the greatest cavity fill ratio and sharpest radius. Temperature had a greater effect on measured properties than either pressure or pressurization rate, although the effect of pressure increased as temperature decreased. The procedures demonstrated in this experimental study could be used to optimize process parameters for robust operation of production applications for more complex automotive body panels fabricated by the warm hydroforming process.
Identifying a Minimal Rheological Configuration: A Tool for Effective and Efficient Constitutive Modeling of Soft Tissues
Authors: Jordan Petr , Kerdok Amy E. , Howe Robert D. , Socrate Simona
Published: March 2011

We describe a modeling methodology intended as a preliminary step in the identification of appropriate constitutive frameworks for the time-dependent response of biological tissues. The modeling approach comprises a customizable rheological network of viscous and elastic elements governed by user-defined 1D constitutive relationships. The model parameters are identified by iterative nonlinear optimization, minimizing the error between experimental and model-predicted structural (load-displacement) tissue response under a specific mode of deformation. We demonstrate the use of this methodology by determining the minimal rheological arrangement, constitutive relationships, and model parameters for the structural response of various soft tissues, including ex vivo perfused porcine liver in indentation, ex vivo porcine brain cortical tissue in indentation, and ex vivo human cervical tissue in unconfined compression. Our results indicate that the identified rheological configurations provide good agreement with experimental data, including multiple constant strain rate load/unload tests and stress relaxation tests. Our experience suggests that the described modeling framework is an efficient tool for exploring a wide array of constitutive relationships and rheological arrangements, which can subsequently serve as a basis for 3D constitutive model development and finite-element implementations. The proposed approach can also be employed as a self-contained tool to obtain simplified 1D phenomenological models of the structural response of biological tissue to single-axis manipulations for applications in haptic technologies.
Detached Eddy Simulation of Atmospheric Flow About a Surface Mounted Cube at High Reynolds Number
Authors: Haupt Sue Ellen , Zajaczkowski Frank J. , Peltier L. Joel
Published: March 2011

Modeling high Reynolds number (Re) flow is important for understanding wind loading on structures, transport and dispersion of airborne contaminants, and turbulence patterns in urban areas. This study reports a high fidelity computational fluid dynamics simulation of flow about a surface mounted cube for a Reynolds number sufficiently high to represent atmospheric flow conditions. Results from detached eddy simulations (DES) and zonal DES that compare well with field experiment data are presented. A study of reducing grid resolution indicates that further grid refinement would not make a significant difference in the flow field, adding confidence in the accuracy of the results. We additionally consider what features are captured by coarser grids. The conclusion is that these methods can produce high fidelity simulations of high Reynolds number atmospheric flow conditions with a modest grid resolution.
Numerical Prediction of Flow Patterns in Bubble Pumps
Authors: Benhmidene Ali , Chaouachi Bechir , Bourouis Mahmoud , Gabsi Slimane
Published: March 2011

In the present study, the ammonia-water mixing flow in a bubble pump is numerically simulated. The flow patterns of a two-phase flow in a bubble pump were studied under different conditions of heat flux and tube diameter. A one-dimensional two-fluid model was developed under constant heat flux. This model was used to predict the variations in void fraction and liquid and vapor velocities throughout the tube. Then, the void fraction profile and the curve of liquid velocity versus vapor velocity were used to predict the flow patterns along the tube length. It was found that at heat fluxes below 15 kW m−2, bubbly, slug, and churn flows are the dominating regimes, and the length of these flow regimes depends on the tube diameter. For heat fluxes higher than 15 kW m−2, the bubble pump operates under the churn and annular regimes, and the bubble pump performance is improved when the tube diameter increases.
A Level Set-Based Topology Optimization Method for Maximizing Thermal Diffusivity in Problems Including Design-Dependent Effects
Authors: Yamada Takayuki , Izui Kazuhiro , Nishiwaki Shinji
Published: March 2011

This paper proposes an optimum design method, based on our level set-based topology optimization method, for maximizing thermal diffusivity in problems dealing with generic heat transfer boundaries that include design-dependent boundary conditions. First, a topology optimization method using a level set model incorporating a fictitious interface energy for regularizing the topology optimization is briefly discussed. Next, an optimization method for maximizing thermal diffusivity is formulated based on the concept of total potential energy. An optimization algorithm that uses the finite element method when solving the equilibrium equation and updating the level set function is then constructed. Finally, several numerical examples are provided to confirm the utility and validity of the proposed topology optimization method.
Layer-to-Layer Height Control for Laser Metal Deposition Process
Authors: Tang Lie , Landers Robert G.
Published: March 2011

A laser metal deposition height control methodology is presented in this paper. The height controller utilizes a particle swarm optimization (PSO) algorithm to estimate model parameters between layers using measured temperature and track height profiles. Using the estimated model, the powder flow rate reference profile, which will produce the desired layer height reference, is then generated using iterative learning control (ILC). The model parameter estimation performance using PSO is evaluated using a four-layer single track deposition, and the powder flow rate reference generation performance using ILC is tested using simulation. The results show that PSO and ILC perform well in estimating model parameters and generating powder flow rate references, respectively. The proposed height control methodology is then tested experimentally for tracking a constant height reference with constant traverse speed and constant laser power. The experimental results indicate that the controller performs well in tracking constant height references in comparison with the widely used fixed process parameter strategy. The application of layer-to-layer height control produces more consistent layer height increment and a more precise track height, which saves machining time and increases powder efficiency.
Investigation on Multi-Pump Liquid-Cooling Loop Based on Thermomagnetic Effect
Authors: Lian Wenlei , Xuan Yimin , Li Qiang
Published: March 2011

When the thermomagnetic convection of a temperature-sensitive magnetic fluid takes place in a loop-shape channel, a continuous circulation of the fluid may be maintained due to the magnetic force resulting from the synergy of external magnetic field and the temperature gradient in the fluid, which plays as a thermomagnetic “pump”. This kind of loops can be used as automatic cooling systems. Researches on such thermomagnetic convection cooling loop have been limited to the “single-pump” situation. In this paper, mathematical models of series-wound and shunt-wound “multi-pump” thermomagnetic convection loops are established by considering the impact of different magnetic fields on each other. The flow and heat transport features of these “multipump” systems are numerically investigated, which are then compared with those in the conventional “single-pump” loop. It is shown that the performance of such a loop is radically changed as more “pumps” join in. The flow and heat transport features of the fluid in a thermomagnetic convection loop system can be easily controlled by the number of “pumps” as well as the way they are connected.
Experimental Investigation of Submerged Impinging Jet Using Cu-Water Nanofluid
Authors: Li Qiang , Xuan Yimin , Yu Feng , Tan Junjie
Published: March 2011

An experimental investigation was performed to study the heat transfer and flow features of Cu-water nanofluids (Cu particles with 26 nm diameter) in a submerged jet impingement cooling system. Three particular nozzle-to-heated surface distances (2, 4 and 6 mm) and four particle volume fractions (1.5%, 2.0%, 2.5% and 3.0%) are involved in the experiment. The experimental results reveal that the suspended nanoparticles increase the heat transfer performance of the base liquid in the jet impingement cooling system. Within the range of experimental parameters considered, it has been found that highest surface heat transfer coefficients can be achieved using a nozzle-to-surface distance of 4 mm and the nanofluid with 3.0% particle volume fraction. In addition, the experiments show that the system pressure drop of the dilute nanofluids is almost equal to that of water under the same entrance velocity.
Development of Advanced Cooling Network Systems for Data Centers
Authors: Abe Yoshiyuki , Ouchi Mayumi , Fukagaya Masato , Kitagawa Takashi , Ohta Haruhiko , Shinmoto Yasuhisa , Sato Masahide , Iimura Ken-ichi
Published: March 2011

Energy utilization in data centers, especially cooling systems for server racks, needs extensive improvement. The present authors proposed advanced cooling network systems for data centers, and R & D activities have been conducted under the so-called Green IT Project sponsored by NEDO (New Energy and Industrial Technology Development Organization). In the present concept, CPUs in servers are cooled down by either direct liquid cooling system or heat pipes with liquid cooling systems in the condensation region. The liquid cooling systems are integrated in each server rack and among server racks. A series of studies on both single phase and two phase narrow channel heat exchangers, high performance heat pipes with self-rewetting fluids and nanofluids for heat transfer enhancement are ongoing. In addition, a prototype server rack with the cooling network systems is also under development toward commercial products. This paper reports the updated status of the present R & D.
Numerical Investigation of a Symmetrical Combustion Burner and External Convection Heat Transfer Characteristics
Authors: Li Xing , Jia Li , Yang Hui
Published: March 2011

Combustion characteristic of natural gas (NG) in a symmetrical combustion chamber and external convection heat transfer characteristic of water flow has been investigated numerically. The burner using a combination of swirling premixed and jet diffusion flames to achieve high flame stability. The combined eddy dissipation model/finite rate chemistry (EDM/FRC) combustion models coupled with RNG k-ε turbulence model were applied to model turbulence combustion. The discrete transfer method (DTM) coupled with weighted sum of gray gas model (WSGGM) were applied to solve the radiation heat transfer. Accurate calculation results were obtained by coupling calculation of combustion in the combustion chamber and external water flow and heat transfer. The temperature fields, heat transfer characteristic in the combustor and water tank were obtained by numerical simulation. The effects of water inlet mass flow rate on combustion and external heat transfer characteristics were discussed. The results indicated that water flow has significant effect on external heat transfer. The temperature distribution is quite uniform in the water tank. Radiation heat transfer plays a dominant role of heat transfer in the combustor.
Turbulent Flow and Heat Transfer in Initial Stage of Ribbed Channel
Authors: Miura Takahiro , Matsubara Koji , Nagai Yoshiyuki , Sakurai Atsushi
Published: March 2011

Direct numerical simulations were performed for air flows and related heat transfer in a developing region of the ribbed channel, where five ribs were attached to one wall. Three rib pitch-to-height ratios, Pi/H = 7, 4 and 2, were considered. The Reynolds number based on the bulk velocity and the channel width was 4,560. For the same parameters, simulations were also made for periodic fully developed cases. Although the largest rib pitch, Pi/H = 7, was the best choice for a heat transfer enhancement ratio in the fully developed cases, the enhancement ratio was larger for the smaller values of rib pitch, Pi/H = 4 or Pi/H = 2 in the initial region. Preference of smaller rib spacing in the initial region was found to come from: (1) the pressure drop was kept low due to the modest meandering of the stream lines; (2) downstream ribs were placed immediately behind the upstream ribs being exposed to the thin thermal layer; (3) the turbulent heat transport was active because of the fluctuation based on the Kelvin-Helmholtz type instability in Pi/H = 4 though fluctuation was weak in Pi/H = 2. Therefore, flow structures positively contributed the heat transfer enhancement of Pi/H = 4 and 2 in the developing region, and the smaller values of the rib pitch was recommended to be selected in such situations.
Numerical Study on Spectral Properties of MIM (AG/MGF2/AG) Structure With Periodic Rectangular Holes
Authors: Xuan Yimin , Gou Yuchun , Han Yuge
Published: March 2011

Spectral properties of metal/insulator/metal (MIM) structure with two-dimensional-hole arrays (2DHAs) are investigated by using the finite-difference time-domain (FDTD) method. The effects of the period, the hole ratio, the thickness of front layer and core layer, and the incident angle as well as the polarization angle on the spectral properties of structured surfaces are studied. It is found that extraordinary optical transmission (EOT) can be excited by the combined effect of waveguide cutoff function and surface plasmon polaritons (SPPs). For some special structure parameters, the MIM structure shows strong absorption of incident wave due to odd mode of SPPs and Fabry–Pe´rot resonance at the sub-wavelength region and relatively longer wavelength region, respectively. These results provide guide information for the application of MIM structure to the EOT devices, absorbers or radiators.
Two-Phase Critical Flow Simulations by Using a New Non-Equilibrium Model and a Modified Equilibrium Model
Authors: Chung Moon-Sun , Yi Sung-Jae , Chang Keun-Shik
Published: March 2011

An accurate prediction of a critical flow discharged from a pressurized pipe system is of most importance in such a safety analysis of nuclear power plants, since it provides the transient boundary conditions during the depressurization transients initiated by a pipe break in primary or secondary systems and during the over-pressurization transients resulting in a relief of coolant through valves. Mass and energy discharge through the opening of pressure boundary affects the system thermal hydraulic responses, that is, phase changes and flow distribution in the system, and the mass inventory remaining in the system necessary to remove core decay heat of a nuclear reactor. Therefore, the safety significance relating to the critical flow led to a development of various empirical and mechanistic critical flow models. However, the accuracies of these models are still in question especially during two-phase critical flow condition. A good example of that is a homogeneous equilibrium model (HEM). The HEM is the basis of several system codes, such as early versions of RELAP, for nuclear loss-of-coolant accident (LOCA). The major non-equilibrium phenomena that are ignored in the HEM are vapor bubble nucleation and interface heat, mass, and momentum transfer. Henry-Fauske empirically handled non-equilibrium vapor generation by introducing a non-equilibrium parameter that allows only a fraction of the equilibrium vapor generation to occur. This approach boils down in essence to a correlation of the deviation between the measured flow rate and the prediction from the HEM: The details of the flow path do not have to be worked out and only needs to know the upstream conditions. However, if we treat non-equilibrium phenomena with this model, it requires an empirical database of the non-equilibrium parameters or their correlations that are so far unknown. Further, because the coefficients are not applied separately to the subcooled liquid and two-phase mixture, we have not been able to treat the non-equilibrium phenomena with the phase change properly. For this reason, we propose the non-equilibrium parameters for subcooled liquid and two-phase mixture, respectively, and then we adopt their combinations according to the flow conditions through the phase change process using the RELAP5/MOD3 code. In addition, we discuss the assessment results of Marviken LBLOCA tests using these non-equilibrium parameter sets with those from the non-equilibrium model by Trapp-Ransom and Chung et al.
Experimental Study on the Flow Regime Identification in the Case of Co-Current Condensation of R134a in a Vertical Smooth Tube
Authors: Dalkilic Ahmet Selim , Wongwises Somchai
Published: March 2011

The present study investigates an intensive comparison of flow regime maps for the verification of annular condensation flow of R134a checked by sight glasses at the inlet and outlet sections of a vertical smooth copper tube having inner diameter of 8.1 mm and a length of 500 mm. R134a and water are used as working fluids in the tube side and annular side of a double tube heat exchanger, respectively. The experimental apparatus are designed to capable of changing the different operating parameters such as mass flow rate, condensation temperature of refrigerant, cooling water temperature and mass flow rate of cooling water etc. and investigate their effect on heat transfer coefficients and pressure drops. Condensation experiments are performed at the mass flux of 456 kg m−2s−1, the saturation temperature is around 40°C, heat fluxes and average qualities are between 16.16–50.89 kW m−2 and 0.81–0.93 respectively. Considering Chen et al.’s annular flow theory on the heat transfer coefficients that are independent from tube orientation as long as annular flow exists along the tube length, experimental data belong to annular flow inside the test tube are plotted on the various flow regime maps and used in the flow regime identification correlations proposed for two-phase flow in horizontal and vertical tubes separately. In spite of their different operating conditions, Barnea et al., Hewitt and Robertson, Baker, Thome, Kattan et al., Chen et al.’s flow regime maps and Taitel and Dukler’s, Dobson’s, Akbar et al.’s, Breber et al.’s, Cavallini et al.’s, Soliman’s flow pattern correlations from literature are found to be predictive for the annular flow conditions in the test tube.