bluuebunny/crossref_metadata_2025 huggingface dataset:
Detection of the Siphon Internal Carotid Artery Stenosis: Transcranial Doppler versus Digital Subtraction Angiography
Authors: You Yong , Hao Qing , Leung Thomas , Mok Vincent , Chen Xiangyan , Lau Alex , Leung Howan , Wong Ka Sing
Published: November 2009

BACKGROUND

Transcranial Doppler (TCD) is widely applied to evaluate the intracranial large artery stenosis. We aimed to evaluate the accuracy of TCD in detecting siphon internal carotid artery (SICA) stenosis against digital subtraction angiography (DSA).

METHODS

A total of 145 patients with TCD and DSA performed were recruited. The SICA and other intracranial arteries were evaluated through transorbital and transtemporal acoustic window by TCD. We defined the best cutoff value for significant SICA stenosis by receiver‐operating characteristic (ROC) curve analyses and calculated the sensitivity, specificity, and positive and negative predictive values (PPV and NPV).

RESULTS

Mean age of the patients was 65.7 years (range 28‐88 years) and 75.1% (109/145) were men. The peak systolic velocity (PSV) = 120 cm/second had the largest area under the ROC curve (area under the ROC curve = .868) compared with the MFV = 70 cm/second and MFV = 80 cm/second (area under the ROC curve = .822 and .845). So the criteria for SICA stenoses were defined as PSV = 120 cm/second plus additional parameters (abnormal spectrum, circumscribed velocity changes, or side‐to‐side difference). Twenty‐nine patients were diagnosed with SICA stenosis or occlusion on TCD. Fourteen patients had abnormal TCD findings that were not confirmed by DSA. One patient with normal TCD but DSA showed mild (40%) stenoses. Accuracy parameters for TCD were as follows: sensitivity = 96.7% (95% confidence interval [CI]= 80.9‐99.8), specificity = 93.9% (95% CI = 89.9‐96.4), PPV = 65.9% (95% CI = 50.0‐79.1), NPV = 99.6% (95% CI = 97.2‐1.0). Most false‐positive patients (11 of 15 patients) had other significant intracranial large arteries lesions.

CONCLUSIONS

The criteria have limited but acceptable sensitivity and specificity in detecting SICA stenoses. Abnormal findings of siphon carotid on TCD require further clarification.
Myocardial Stress Perfusion with a Novel Dual‐Source CT Scanner – Technical Update and Initial Clinical Experience
Authors: Bamberg F. , Nikolaou K. , Becker A. , Klotz E. , Schmidt B. , Flohr T.
Published: November 2009

Traditionally, myocardial perfusion imaging by CT has been hampered by limited detector size and stability of Hounsfield Units in moving cardiac acquisition modes. In the present article, we describe the technical principles of a novel, dynamic heart shuttle scan acquisition using a second generation dual source CT system (SOMATOM Definition Flash, Siemens Healthcare, Forchheim, Germany). With simultaneous injection of iodinated contrast agent, this protocol allows for sequential assessment of myocardial enhancement with reasonable radiation exposure of less than 10 mSv. We also present the case of a 69‐year‐old male patient who underwent dynamic CT‐based myocardial perfusion imaging to determine the hemodynamic relevance of a stenosis in the left anterior descending coronary artery.
A clinical review of 105 patients with PFAPA (a periodic fever syndrome)
Authors: Feder HM , Salazar JC
Published: November 2009

Aims: We describe the presentations and clinical outcomes of pediatric patients diagnosed with PFAPA (Periodic Fever, Aphthous lesions, Pharyngitis, and cervical Adenitis).

Materials and methods: The medical records of children with recurrent fever and referred between 1998 and 2007 to a tertiary pediatric care hospital were reviewed. Children who met clinical criteria for PFAPA were then asked to participate in a follow‐up study.

Results: One hundred and five children met study criteria for PFAPA which included at least six episodes of periodic fever. Most (62%) were males, the mean age at onset of PFAPA was 39.6 months (80% were <5 years at onset), the mean duration of individual fever episodes was 4.1 days, and the mean interval between episodes was 29.8 days. Accompanying signs and symptoms included aphthous stomatitis (38%), pharyngitis (85%), cervical adenitis (62%), headache (44%), vomiting with fever spikes (27%) and mild abdominal pain (41%). A prodrome (usually fatigue) preceded the fever in 62% of patients. Parents noted that when their child with PFAPA had fever, other family members remained well. Laboratory tests in patients with PFAPA were nonspecific. Individual episodes of fever usually resolved with a single oral dose (∼1 mg/kg) of prednisilone. The interval between fever episodes shortened in 50% of patients who used prednisilone. PFAPA resolved spontaneously (mean length 33.2 months) in 211105 (20%) patients. PFAF’A episodes continued (mean length 23 months) at the end of this study in 661105 (63%) patients. Cimetidine therapy was associated with the resolution of the fevers in 7/26 (27%) patients; tonsillectomy was associated with the resolution of the fevers in 11/11 (100%) patients.

Conclusion: PFAPA can usually be defined by its clinical characteristics. Individual febrile episodes usually resolve dramatically with oral prednisilone. The cause of PFAPA is unknown and research is needed to define its etiology. The overall prognosis for children with PFAPA is excellent.
The prognostic value of amplitude integrated EEG in neonatal sepsis and/or meningitis
Authors: Ter Horst HJ , Van Olffen M , Remmelts HJ , De Vries H , Bos AF
Published: November 2009

Aim:  To investigate the longitudinal course and prognostic value of amplitude integrated EEG (aEEG) in infants with neonatal sepsis or meningitis.

Methods:  Amplitude integrated EEG recordings of 22 infants with sepsis/meningitis were retrospectively evaluated. Mean gestational age was 38 weeks (range: 34–42 weeks). Thirteen infants had meningitis. Survivors were seen for neurological follow‐up. Four infants died, two were severely abnormal at 24 months. Amplitude integrated EEG background pattern, sleep wake cycling (SWC) and electrographic seizure activity (EA) were appraised.

Results:  All infants with continuous low voltage or flat trace on aEEG (n = 4) had an adverse outcome. Low voltage aEEGs (n = 9) had a positive LR (LR+) for an adverse outcome of 5.3 (95% CI: 1.9–14.8) at 6 h and 8.3 (95% CI: 1.3–55) at 24 h after admission. EA was more frequent in infants with adverse outcome (p < 0.01) and had a LR+ for adverse outcome of 10.6 (95% CI: 1.5–76). SWC appeared more frequent in infants with good outcome (p < 0.05).

Conclusion:  Low voltage background pattern, SWC and EA on aEEG are helpful to predict neurological outcome in infants with neonatal sepsis or meningitis.
The X‐Ray Structure of Carboxypeptidase A Inhibited by a Thiirane Mechanism‐Based Inhibitor
Authors: Fernández Daniel , Testero Sebastian , Vendrell Josep , Avilés Francesc X. , Mobashery Shahriar
Published: November 2009

The three‐dimensional X‐ray crystal structure of carboxypeptidase A, a zinc‐dependent hydrolase, covalently modified by a mechanism‐based thiirane inactivator, 2‐benzyl‐3,4‐epithiobutanoic acid, has been solved to 1.38 Å resolution. The interaction of the thiirane moiety of the inhibitor with the active site zinc ion promotes its covalent modification of Glu‐270 with the attendant opening of the thiirane ring. The crystal structure determination at high resolution allowed for the clear visualization of the covalent ester bond to the glutamate side chain. The newly generated thiol from the inhibitor binds to the catalytic zinc ion in a monodentate manner, inducing a change in the zinc ion geometry and coordination, while its benzyl group fits into the S1’ specificity pocket of the enzyme. The inhibitor molecule is distorted at the position of the carbon atom that is involved in the ester bond linkage on one side and the zinc coordination on the other. This particular type of thiirane‐based metalloprotease inhibitor is for the first time analyzed in complex to the target protease at high resolution and may be used as a general model for zinc‐dependent proteases.
Arterial Occlusion Sites on Magnetic Resonance Angiography Influence the Efficacy of Intravenous Low-Dose (0·6 mg/kg) Alteplase Therapy for Ischaemic Stroke
Authors: Nakashima T. , Toyoda K. , Koga M. , Matsuoka H. , Nagatsuka K. , Takada T. , Naritomi H. , Minematsu K.
Published: November 2009

Aims

To determine the predictors of efficacy, including magnetic resonance imaging information, for low-dose intravenous alteplase therapy for stroke patients.

Methods

Seventy-eight patients were prospectively enrolled in a single Stroke Unit (SU) receiving alteplase at a dose of 0·6 mg/kg during the initial 27 months after its approval in Japan. Ischaemic changes and vascular lesions were identified using computed tomography, diffusion-weighted magnetic resonance imaging, and magnetic resonance angiography. Early ischaemic signs were assessed using the Alberta Stroke Program Early CT Score.

Results

The median baseline National Institutes of Health Stroke Scale score of 78 patients was 12. In 19 patients (24%), the National Institutes of Health Stroke Scale score improved by ≥8 points at 24 h. After multivariate adjustment, occlusion at the internal carotid artery (odds ratio 11·82, 95% confidence interval 1·73–142·74), Alberta Stroke Program Early CT Score on diffusion-weighted imaging ≤6 (15·23, 1·88–351·50), and a lower National Institutes of Health Stroke Scale score (1·24, 1·08–1·47, per 1-point decrease) were inversely correlated with early improvement. Four patients (5%) had symptomatic intracranial haemorrhage. At 3 months, 76 patients (98%) survived, and 36 of 78 patients (46%) overall, but only two of 19 patients (11%) with internal carotid artery occlusion, had a favourable functional outcome, corresponding to a modified Rankin scale score 1. After multivariate adjustment, internal carotid artery occlusion (odds ratio 15·84, 95% confidence interval 3·12–128·69) and Alberta Stroke Program Early CT Score on diffusion-weighted imaging ≤6(15·62, 1·78–410·12) were independent predictors of poor outcome.

Conclusions

Intravenous alteplase therapy at a dose of 0·6 mg/kg resulted in a relatively good overall outcome when compared with outcomes reported by western studies using an alteplase dose of 0·9 mg/kg. However, patients with occlusion at the internal carotid artery did not respond to this low-dose alteplase therapy.
Implant for Augmentation of Cerebral Blood Flow Trial 1: A Pilot Study Evaluating the Safety and Effectiveness of the Ischaemic Stroke System for Treatment of Acute Ischaemic Stroke
Authors: Khurana D. , Kaul S. , Bornstein N. M.
Published: November 2009

Introduction

In rat stroke models, sphenopalatine ganglion stimulation up to 24 h after stroke onset augments cerebral blood flow, reduces infarct volume and improves neurological deficits. The ischaemic stroke system 500 has been designed to stimulate the sphenopalatine ganglion in humans.

Objectives

( 1 ) To determine the safety and tolerability of the ischaemic stroke system 500 in acute ischaemic stroke within 24 h of stroke onset. ( 2 ) To determine the effectiveness of ischaemic stroke system 500 in acute ischaemic stroke treatment.

Design/Methods

Implant for augmentation of cerebral blood flow trial-1 is a multi-national open-label study in patients of acute ischaemic stroke in the anterior circulation with National Institutes of Health Stroke Scales 7–20. The treatment initiation will be within 24 h of stroke onset. The ischaemic stroke system is implanted adjacent to the sphenopalatine ganglion via the greater palatine canal using local anaesthesia and a minimally invasive approach. The treatment protocol is constituted as 3–4 h of daily stimulation over 5–7 days. Conclusions The implant for augmentation of cerebral blood flow trial-1 will determine the safety and tolerability of the ischaemic stroke system 500 in acute ischaemic stroke as reflected by the incidence of adverse events.
Oxidative Stress and Its Role in the Pathogenesis of Ischaemic Stroke
Authors: Allen C. L. , Bayraktutan U.
Published: November 2009

Stroke is one of the leading causes of mortality and morbidity, with astronomical financial repercussions on health systems worldwide. Ischaemic stroke accounts for approximately 80–85% of all cases and is characterised by the disruption of cerebral blood flow and lack of oxygen to the affected area. Oxidative stress culminates due to an imbalance between pro-oxidants and antioxidants and consequent excessive production of reactive oxygen species. Reactive oxygen species are biphasic, playing a role in normal physiological processes and are also implicated in a number of disease processes, whereby they mediate damage to cell structures, including lipids, membranes, proteins, and DNA. The cerebral vasculature is a major target of oxidative stress playing a critical role in the pathogenesis of ischaemic brain injury following a cerebrovascular attack. Superoxide, the primary reactive oxygen species, and its derivatives have been shown to cause vasodilatation via the opening of potassium channels and altered vascular reactivity, breakdown of the blood-brain barrier and focal destructive lesions in animal models of ischaemic stroke. However, reactive oxygen species are involved in normal physiological processes including cell signalling, induction of mitogenesis, and immune defence. Primarily, this review will focus on the cellular and vascular aspects of reactive oxygen and nitrogen species generation and their role in the pathogenesis of ischaemia–reperfusion phenomena. Secondly, the proposed mechanisms of oxidative stress-related neuronal death will be reflected upon and in summation specific targeted neuroprotective therapies targetting oxidative stress and their role in the pathogenesis of stroke will be discussed.
Food use and nutrient intake at worksite canteen or in packed lunches at work among Finnish employees
Authors: Raulio Susanna , Roos Eva , Ovaskainen Marja‐Leena , Prättälä Ritva
Published: November 2009

Finnish employees have lunch at worksite canteens or have packed lunch, but the nutritional quality of neither is known. We investigated the food use and nutrient intake of Finnish employees who eat either at worksite canteens vis‐à‐vis those who eat packed lunches. Dietary data were collected by a 48‐hour‐dietary‐recall in the FINDIET 2002 survey. Employed Finns aged 25–64 years were included (n = 261). Men ate more fresh vegetables and salad dressing at the canteen than in packed lunches. Women consumed more fresh vegetables, vegetable foods and fish dishes at canteens. Among men, energy, vitamin A and carotenoid intake from canteen lunches were higher than from packed lunches. Among women, the canteen users got more energy and fat, but fewer carbohydrates and less sugar and fibre. Even though the nutritional differences in the meals eaten at different places were modest, eating at the canteen improved the diets of employees by increasing their vegetable intake.
Lethal and sub‐lethal effects of ivermectin on north temperate dung beetles,Aphodius aterandAphodius rufipes(Coleoptera: Scarabaeidae)
Authors: O’HEA NORMA M. , KIRWAN LAURA , GILLER PAUL S. , FINN JOHN A.
Published: November 2009

Abstract. 1. Ivermectin is an anthelmintic veterinary medicine, and is excreted in the dung of treated livestock in a mainly unmetabolised form. Ivermectin is known to have toxic effects on dung beetles, but most studies to date have been conducted on tropical and sub‐tropical species. Relatively few laboratory studies have focused on the specific effects of ivermectin on survival and development of north temperate dung beetles.

2. In this study, we experimentally investigated the effect of ivermectin concentration on various life stages of twoAphodiusdung beetle species. Dung was collected from cattle groups that had been treated with a subcutaneous injection of ivermectin. Laboratory bioassays were conducted by feeding adults of two beetle species (Aphodius aterandAphodius rufipes) with dung that contained different concentrations of ivermectin. Adult survival and oviposition were measured, and the subsequent development and survival of produced larvae was monitored over time.

3. Larval development rates were significantly slowed by ivermectin. Ivermectin had significant negative effects on the survival of larvae. Overall, ivermectin concentration caused large and significant reductions in the cohort size from an individual dung pat that would potentially contribute to the next generation of beetles.

4. In general, ivermectin concentration did not have significant negative effects on adult survival. The number of eggs per femaleA. rufipeswas significantly reduced by ivermectin concentration in one of two bioassays, but the magnitude of the effect was not large. The actual impacts on dung beetle population dynamics in farmland would depend on several other factors, which are discussed.
A PCR‐based method for diet analysis in freshwater organisms using 18S rDNA barcoding on faeces
Authors: CORSE EMMANUEL , COSTEDOAT CAROLINE , CHAPPAZ RÉMI , PECH NICOLAS , MARTIN JEAN‐FRANÇOIS , GILLES ANDRÉ
Published: November 2009

The development of DNA barcoding from faeces represents a promising method for animal diet analysis. However, current studies mainly rely on prior knowledge of prey diversity for a specific predator rather than on a range of its potential prey species. Considering that the feeding behaviour of teleosts may evolve with their environment, it could prove difficult to establish an exhaustive listing of their prey. In this article, we extend the DNA barcoding approach to diet analysis to allow the inclusion of a wide taxonomic range of potential prey items. Thirty‐four ecological clade‐specific primer sets were designed to cover a large proportion of prey species found in European river ecosystems. Selected primers sets were tested on isolated animal, algal or plant tissues and thereafter on fish faeces using nested PCR to increase DNA detection sensitivity. The PCR products were sequenced and analysed to confirm the identity of the taxa and to validate the method. The methodology developed here was applied to a diet analysis of three freshwater cyprinid species that are assumed to have similar feeding behaviour [Chondrostoma toxostoma toxostoma (Vallot 1837), Chondrostoma nasus nasus (Linnaeus, 1758) and Barbus barbus, (Linneaus 1758)]. These three species were sampled in four different hydrographic basins. Principal Component Analysis based on prey proportions identified distinct perilithon grazer and benthophagous behaviours. Furthermore, our results were consistent with the available literature on feeding behaviour in these fish. The simplicity of the PCR‐based method and its potential generalization to other freshwater organisms may open new perspectives in food web ecology.
Galantamine‐ER For Cognitive Dysfunction In Bipolar Disorder and Correlation with Hippocampal Neuronal Viability: A Proof‐of‐Concept Study
Authors: Iosifescu Dan V. , Moore Constance M. , Deckersbach Thilo , Tilley Claire A. , Ostacher Michael J. , Sachs Gary S. , Nierenberg Andrew A.
Published: November 2009

Background: Many subjects with bipolar disorder experience significant cognitive dysfunction, even when euthymic, but few studies assess biological correlates of or treatment strategies for cognitive dysfunction.

Method: Nineteen subjects with bipolar disorder in remission, who reported subjective cognitive deficits, were treated with open‐label galantamine‐ER 8–24 mg/day for 4 months. Ten healthy volunteers matched for age and gender were also assessed. Mood and subjective cognitive questionnaires were administered monthly. At the beginning and the end of the trial all subjects were administered neuropsychological tests, including tests of attention (Conners CPT) and episodic memory (CVLT). Bipolar subjects underwent proton magnetic resonance spectroscopy (1H‐MRS) measurements before and after treatment, healthy volunteers completed baseline 1H‐MRS. We acquired 1H‐MRS data at 4.0 T from voxels centered on the left and right hippocampus to measure hippocampal N‐acetyl aspartate (NAA, a measure of neuronal viability) and choline containing compounds (Cho, a marker of lipid metabolism and membrane turn‐over).

Results: Compared to healthy volunteers, bipolar subjects had higher baseline subjective cognitive deficits and lower scores on objective tests of attention (Conner's CPT) and verbal episodic memory (CVLT). After treatment, bipolar subjects experienced significant improvement of subjective cognitive scores and on objective tests of attention (Conner's CPT) and verbal episodic memory (CVLT). In the left hippocampus NAA increased and choline (Cho) decreased in bipolar subjects during treatment.

Conclusion: Bipolar subjects had cognitive dysfunction; treatment with Galantamine‐ER was associated with improved cognition and with increases in neuronal viability and normalization of lipid membrane metabolism in the left hippocampus.

This study was registered on ClinicalTrials.gov (NCT00181636).
RESEARCH: Cognitive Rehabilitation for Bipolar Disorder: An Open Trial for Employed Patients with Residual Depressive Symptoms
Authors: Deckersbach Thilo , Nierenberg Andrew A. , Kessler Ronald , Lund Hannah G. , Ametrano Rebecca M. , Sachs Gary , Rauch Scott L. , Dougherty Darin
Published: November 2009

Bipolar disorder is characterized by recurrent episodes of depression and/or mania along with interepisodic mood symptoms that interfere with psychosocial functioning. Despite periods of symptomatic recovery, individuals with bipolar disorder often continue to experience impairments in psychosocial functioning, particularly occupational functioning. Two determinants of psychosocial functioning of euthymic (neither fully depressed nor manic) individuals with bipolar disorder are residual depressive symptoms and cognitive impairment (i.e., difficulties with executive functioning, attention, and memory). The present study explored whether a new cognitive remediation (CR) treatment designed to treat residual depressive symptoms and, for the first time to the best of our knowledge, address cognitive impairment would be associated with improvement in psychosocial functioning in individuals with bipolar disorder. Following a neuropsychological and clinical assessment 18 individuals with DSM‐IV bipolar disorder were treated with 14 individual sessions of CR. Results indicated that at the end of treatment, as well as at the 3‐months follow‐up, patients showed lower residual depressive symptoms, and increased occupational, as well as overall psychosocial functioning. Pretreatment neuropsychological impairment predicted treatment response. Improvements in executive functioning were associated with improvements in occupational functioning. These findings suggest that treating residual depressive symptoms and cognitive impairment may be an avenue to improving occupational and overall functioning in individuals with bipolar disorder.
Correlated expression of peroxisome proliferator‐activated receptor γ with high histologic grade and basal type in invasive ductal carcinoma of the breast
Authors: Jeong Hoiseon , Lee Youngseok , An Jungsuk , Woo Ok Hee , Park KyongHwa , Kim Aeree
Published: November 2009

Backgroud and aim: Peroxisome proliferator‐activated receptor γ (PPARγ) is one of the ligand‐activated transcription factors belonging to the nuclear hormone receptor family. The protein is expressed in various kinds of tumor and has been implicated as a tumor suppressor in most cancers. We aimed to understand the role of PPARγ in breast cancer. Methods: The expression of PPARγ in 288 cases of invasive ductal carcinoma was examined using tissue microarray and immunohistochemistry. Results: PPARγ immunoreactivity was detected in 21.5% of cases and significantly associated with expression of EGFR and ki‐67 (P= 0.008; P= 0.046). PPARγ expression was correlated with high histological grade and basal type (P≤ 0.001; P= 0.009). Conclusions: PPARγ expression is related to poor prognostic factors of breast cancer. It is considered that PPARγ has evident tumor promoting properties in vivo, but receptor‐independent effects of PPARγ ligands may compound its biologic effects in cancer. A better understanding of action mechanisms of the activated PPARγ is required.
Study and Optimization of Horizontal-Base Pin-Fin Heat Sinks in Natural Convection and Radiation
Authors: Sahray D. , Shmueli H. , Ziskind G. , Letan R.
Published: November 2009

This paper aims at deeper understanding of heat transfer from horizontal-base pin-fin heat sinks with exposed edges in free convection of air. The effects of fin height and fin population density are studied experimentally and numerically. The sinks are made of aluminum, and there is no contact resistance between the base and the fins. All the sinks studied have the same base dimensions and are heated using foil electrical heaters. The fins have a constant square cross section, whereas the fin height and pitch vary. The heat input is set, and temperatures of the base and fins are measured. In the corresponding numerical study, the sinks and their environment are modeled using the FLUENT 6.3 software. The results show that heat-transfer enhancement due to the fins is not monotonic. The differences between sparsely and densely populated sinks are assessed quantitatively and analyzed for various fin heights. Also analyzed is the heat flux distribution at the edges and center of the sink. A relative contribution of outer and inner fin rows in the sink is assessed, together with the effect of fin location in the array on the heat-transfer rate from an individual fin. By decoupling convection from radiation, a dimensional analysis of the results for natural convection is attempted. A correlation presenting the Nusselt number versus the Rayleigh number is suggested, where the “clear” spacing between fins serves as the characteristic length.
Optimal Distribution of Heat Sources in Convergent Channels Cooled by Laminar Forced Convection
Authors: Jassim E. , Muzychka Y. S.
Published: November 2009

The constructal theory is applied to the flow in a convergent channel. The primary goals of this work are to analyze the heat source distribution and generalize the formula concerning such configurations, to study the spacing between consecutive elements, and to verify the analysis by comparing the proposed configuration with numerical simulations. The results show that nonuniform distributions enhance the performance of the system by allowing the heat source element to work near its maximum condition. Furthermore, the optimal distribution occurs when the heat sources are placed closer to each other near the leading edge of the channel. While the literature shows that the spacing between any consecutive element increases as the sources move downstream from the leading edge, the present results proved that such conclusions are restricted, depending on the ratio of outlet to inlet freestream velocity. Accordingly, the spacing has a maximum value when the exit freestream velocity is more than twice that of the inlet. For design issues, the study also addresses the minimum heat required to achieve optimal system performance. The results show that the amount of heat needed by the system to work close to its optimal performance varies exponentially with the convergent angle and increases with the increase in the heating element’s width. The comparison of the present distribution of the heat source elements with a regular one (fixed spacing) is performed numerically to demonstrate the efficiency of the proposed configuration. The results show that the present model forces the system to work more efficiently than the uniform distribution.
Non-Darcy Mixed Convection With Thermal Dispersion in a Saturated Porous Medium
Authors: Sobha V. V. , Vasudeva R. Y. , Ramakrishna K. , Latha K. Hema
Published: November 2009

Thermal dispersion due to local flows is significant in heat transfer with forced convection in porous media. The effects of parametrized melting (M), thermal dispersion (D), inertia (F), and mixed convection (Ra/Pe) on the velocity distribution, temperature, and Nusselt number on non-Darcy, mixed convective heat transfer from an infinite vertical plate embedded in a saturated porous medium are examined. It is observed that the Nusselt number decreases with increase in melting parameter and increases with increase in thermal dispersion.
Optimal Heat Distribution Among Discrete Protruding Heat Sources in a Vertical Duct: A Combined Numerical and Experimental Study
Authors: Sudhakar T. V. V. , Shori Arun , Balaji C. , Venkateshan S. P.
Published: November 2009

This paper reports the results of experimental and numerical investigations of optimal heat distribution among the protruding heat sources under laminar conjugate mixed convection heat transfer in a vertical duct. A printed circuit board with 15 heat sources forms a wall of a duct. Three-dimensional governing equations of flow and heat transfer were solved in the flow domain along with the energy equation in the solid domain using FLUENT 6.3. A database of temperatures of each of the heat sources for different heat distributions is generated numerically. Artificial neural networks (ANNs) were used as a forward model to replace the time consuming complex computational fluid dynamics (CFD) simulations. The functional relationship between heat input distribution and the corresponding temperatures of the heat sources obtained by training the network is used to drive a genetic algorithm based optimization procedure to determine the optimal heat distribution. The optimal distribution here refers to the apportioning of a fixed quantity of heat among 15 heat sources, keeping the maximum of the temperatures of the heat sources to a minimum. Furthermore, the heat distribution corresponding to a set of specified target temperatures of the heat sources is obtained using a network that is trained and tested with a database of temperatures of the heat sources generated using FLUENT 6.3 in the range of total heat dissipation of 5–25 W. Using this network, it was possible to maximize the total heat dissipation from the heat sources for a given target temperature directly. In order to validate the optimization method, a low speed vertical wind tunnel has been used to carry out the mixed convection experiments for different combinations of heat distribution and also for the optimal heat distribution, and the temperatures of the heat sources were measured. The results of the numerical simulations, ANN, and the corresponding experimental results are in good agreement.
Thermal Protection of a Ground Layer With Phase Change Materials
Authors: Duan X. , Naterer G. F.
Published: November 2009

Conventional ground surface insulation can be used to protect power line foundations in permafrost regions from the adverse effects of seasonal freezing and thawing cycles. But previous studies have shown ineffective thermal protection against the receding permafrost with conventional insulation. In this paper, an alternative thermal protection method (phase change materials (PCMs)) is analyzed and studied experimentally. Seasonal ground temperature variations are estimated by an analytical conduction model, with a sinusoidal ground surface temperature variation. A compensation function is introduced to predict temperature variations in the foundation, when the ground surface reaches a certain temperature profile. Measured data are acquired from an experimental test cell to simulate the tower foundation. With thermal energy storage in the PCM layer, the surface temperature of the soil was modified, leading to changes in temperature in the foundation. Measured temperature data show that the PCM thermal barrier effectively reduces the temperature variation amplitude in the foundation, thereby alleviating the seasonal freezing and thawing cycles. Different thermal effects of the PCM thermal barrier were obtained under different air temperature conditions. These are analyzed via melting degree hours and freezing degree hours, compared with a critical number of degree hours.
Modeling the Instability of Carbon Nanotubes: From Continuum Mechanics to Molecular Dynamics
Authors: Duan Wen Hui , Wang Qing , Wang Quan , Liew Kim Meow
Published: November 2009

A hybrid continuum mechanics and molecular mechanics model is developed in this paper to predict the critical strain, stress, and buckling load of the inelastic buckling of carbon nanotubes. With the proposed model, the beamlike and shell-like buckling behavior of carbon nanotubes can be analyzed in a unified approach. The buckling solutions from the hybrid model are verified from molecular dynamics simulations via the MATERIALS STUDIO software package and from available research findings. The existence of the optimum diameter, at which the buckling load reaches its maximum, and the correlation of the diameter with the length of carbon nanotubes, as predicted by Liew et al. (2004, “Nanomechanics of Single and Multiwalled Carbon Nanotubes,” Phys. Rev. B, 69(11), pp. 115429), are uncovered by the hybrid model. The simplicity and effectiveness of the proposed model are not only able to reveal the chiral and size-dependent buckling solutions for carbon nanotubes, but also enable a thorough understanding of the stability behavior of carbon nanotubes in potential applications.
Molecular Motors as Components of Future Medical Devices and Engineered Materials
Authors: Agarwal Ashutosh , Hess Henry
Published: November 2009

A new frontier in the development of prosthetic devices is the design of nanoscale systems which replace, augment, or support individual cells. Similar to cells, such devices will require the ability to generate mechanical movement, either for transport or actuation. Here, the development of nanoscale transport systems, which integrate biomolecular motors, is reviewed. To date, close to 100 publications have explored the design of such “molecular shuttles” based on the integration of synthetic molecules, nano- and microparticles, and micropatterned structures with kinesin and myosin motors and their associated cytoskeletal filaments, microtubules, and actin filaments. Tremendous progress has been made in addressing the key challenges of guiding, loading, and controlling the shuttles, providing a foundation for the exploration of applications in medicine and engineering.
Novel Design of Carbon Nanotube Based RF Inductors
Authors: Kim Bruce C.
Published: November 2009

In this paper, we describe the design and simulation of multiwall carbon nanotube (MWCNT) based stacked inductors, which provide high inductance and quality values that are suitable for next-generation rf products. We have designed novel stacked MWCNT-based embedded rf inductors on silicon and ceramic substrates.
Predicting Temperatures in Flowing Oil Wells
Authors: Shiu K. C. , Beggs H. D.
Published: November 2009

An empirical method is presented for calculating temperature profiles in flowing oil wells. The method is applicable to wells in which two-phase flow is occurring and in which the inlet fluid temperature is known. It was developed from field data and can be used in design problems which require accurate subsurface temperatures, such as flowing pressure traverse calculation and gas-lift design.
Submerged Production System—A Final Report
Authors: Burkhardt J. A. , Childers T. W. , Anderson R. E. , Loth W. D. , Michie T. W.
Published: November 2009

The offshore pilot test of Exxon’s Submerged Production System (SPS) has reached a successful conclusion. This pilot test encompassed the entire spectrum of SPS equipment, spanning from the well completion intervals to, but not including, common surface processing and storage facilities. Since the SPS is designed to meet all the life cycle needs of a subsea field, one of the objectives of the pilot test was to evaluate both the techniques and the equipment used to install, operate, and maintain a prototype version of the SPS. The equipment under test was designed for use in water depths up to 2000 ft, but with minor modifications it is capable of operating in significantly greater depths. Evaluation of pilot test results has shown that the deep water installation techniques are practicable and that the deep water maintenance machinery is competent to repair any failures likely to occur in an operating system. One of the most significant problems in conducting the pilot test was achieving adequate quality control during equipment manufacture. The test results have demonstrated that, with relatively minor modifications, the SPS is suitable for commercial application.
Dynamics of Suspended Marine Pipelines
Authors: Hall J. E. , Healey A. J.
Published: November 2009

As the development of offshore oil and gas production proceeds, the dynamic stresses in pipelines induced by laying operations become more important. The contribution of this paper is to the finite-element modelling of the dynamics of a large pipeline where nonlinear bottom reactions and ocean fluid drag are included. A time domain simulation procedure is described for computing the dynamic motion and stress response for arbitrary time history inputs at the surface. Also, a method of linearizing the seaway fluid drag terms and of handling the nonlinear bottom reactions is shown for harmonic seaway inputs. The two methods are compared and illustrate the reasonable accuracy of the linearized method. It is shown that dynamic bending stressess can be significant in the sag bend regions indicating the need for evaluation for future deep water applications. Additionally, it was found that dynamic bending stress magnitudes increased with ocean bottom rigidity. The model concentrates on the pipeline analysis and assumes a ramp-style stinger, the dynamics of which has not been included.
Selection and Sizing of Velocity-Actuated Subsurface Safety Valves
Authors: Beggs H. D. , Brill J. P. , Proan˜o E. A. , Roman-Lazo C. E.
Published: November 2009

Subsurface safety valves (SSSVs) are installed in offshore oil and gas wells to shut in the wells in case of pressure loss at the wellhead. The selection of these SSSVs requires prediction of the oil and gas flow rates at which the valve will close. A study was performed to improve the design criteria used in the selection. Improved correlations were developed to predict pressure drop across a SSSV as a function of flow rates, and the pressure drop at which a SSSV will close.
Theoretical and Experimental Research on Hydraulic Fracturing
Authors: Hanson M. E. , Anderson G. D. , Shaffer R. J.
Published: November 2009

We are conducting a joint theoretical/experimental research program on hydraulic fracturing. Newly developed two-dimensional numerical models (which include complete descriptions of the elastic continuum and porous flow fluids) have been applied to analyze the effects of pore pressure on the fracturing process. By means of small-scale experiments, we are acquiring a better understanding of the effects of the in-situ stress field, the porosity and permeability of the solid, and the presence of interfaces or layering in the solid. Experimentally, we have been studying the growth of cracks near an interface in several materials, including polymethylmethacrylate (PMMA), Nugget sandstone, and Indiana limestone. Results have shown that the mechanical properties of the interface relative to the properties of the materials on either side are important. A crack will not cross a well-bonded interface between two pieces of PMMA, even in the presence of a 13.79-MPa (2000-psi) normal load. Cracks will cross a well-bonded interface from PMMA to limestone, but not vice versa. Similarly, cracks will propagate across a bonded interface from Nugget sandstone to limestone, but not the other way. Pressure-driven cracks will cross an unbonded interface between limestone blocks at normal loads as low as 3.45 MPa (500 psi).
A Technique and Computer Program for Predicting Far Field Noise Levels from Piping Runs
Authors: Ajax M. F.
Published: November 2009

Acoustic energy as radiated from effective incremental cylindrical surfaces is considered, which during the course of initial propagation are assumed to become hemisperhical and divergent. These are summed along piping runs under chosen gradient conditions representing an intensity decay along the pipe. A computer program for scanning the geometry of these incremental radiating surfaces is provided to include the effect of barriers in the line of propagation. Printout is both octave-band and “A” weighted.
Breaking Ice with Gravity Waves
Authors: Bates H. F. , Shapiro L. H.
Published: November 2009

The plane-wave impulse response of a laterally compressed floating elastic plate, derived in earlier work, provides a simple means of describing the response of a floating ice sheet to gravity waves induced by a moving vehicle. Vehicle speeds above the cut-off phase velocity produce gravity waves that grow in amplitude with time. These waves grow in amplitude most rapidly when the vehicle speed equals the critical gravity-wave phase velocity. For vehicle speeds above the critical phase velocity, the critical wave is excited at an angle to the vehicle motion; hence, the amplitude grows at a high but decreasing rate as the vehicle speed increases from the critical speed. The critical speed is the optimum speed for breaking an ice sheet by moving vehicle. Vehicles travelling at speeds below the cut-off phase velocity do not excite growing waves that increase the deflection of the ice sheet; thus, vehicular travel below the cut-off speed is recommended. Easily derived plots of the cut-off and critical phase velocities and wave lengths are presented as functions of ice thickness and water depth.
OTEC Power System Modeling, Analysis and Design via Geometric Programming
Authors: Lavi A.
Published: November 2009

A complex power system may be modeled by a system of inequalities representing the constraints imposed by the physical laws: heat transfer, energy balance, cycle efficiency and so forth. The nature of the resulting mathematical model is such that the terms contain complex expressions involving the design and operating variables of the process. With the addition of an objective function involving the cost of major system components, a multivariable nonlinear programming problem can be formulated. Seldom does the model lend itself to analytical treatment. This paper is concerned with a specific formulation and solution of nonlinear programming problems which arise in the design of ocean thermal energy conversion (OTEC) power plants. The technique used is geometric programming, GP. It is shown that GP serves as an excellent tool for system analysis because it provides sensitivity information essential to the designer.
Utilization of Fluidized Bed Combustion in Energy Recovery from Solid Wastes
Authors: Hamm J. R. , Keairns D. L.
Published: November 2009

Fluidized bed combustion is capable of utilizing a wider variety of fuels (including solid wastes) than is any other combustion process. Thus, it has the potential for wide application in systems for recovering energy from solid wastes in industry, commercial sites, institutions, forestry, and agriculture to produce electric power, process steam, process heat, and space heating. Three fluidized bed combustion concepts are identified for near-term application: atmospheric fluidized bed boiler, exhaust-heated gas turbine or combined cycle, and closed-cycle gas turbine.
Thermodynamic and Economic Analysis of Heat Pumps for Energy Recovery in Industrial Processes
Authors: Urdaneta-B A. H. , Schmidt P. S.
Published: November 2009

A computer code has been developed for analyzing the thermodynamic performance, cost and economic return for heat pump applications in industrial heat recovery. Starting with basic defining characteristics of the waste heat stream and the desired heat sink, the algorithm first evaluates the potential for conventional heat recovery with heat exchangers, and if applicable, sizes the exchanger. A heat pump system is then designed to process the residual heating and cooling requirements of the streams. In configuring the heat pump, the program searches a number of parameters, including condenser temperature, evaporator temperature, and condenser and evaporator approaches. All system components are sized for each set of parameters, and economic return is estimated and compared with system economics for conventional processing of the heated and cooled streams (i.e., with process heaters and coolers). Several thermodynamic and economic performance ratios are computed for comparative evaluation of heat pumps versus conventional systems. Two case studies are evaluated, one in a food processing application and the other in an oil refinery unit. Results of the case studies are presented to illustrate the use of the program and to show the sensitivity of heat pump system economics to the various design parameters.
A Three-Dimensional Anisotropic Yield Condition for Green River Shale
Authors: Smith M. B. , Cheatham J. B.
Published: November 2009

A three-dimensional, transversely isotropic yield condition is combined with a plane of weakness to describe the initial yield limit for Green River Shale. This theory is compared to experimental results for two different qualities of oil shale, including true three-dimensional tri-axial stress tests. It is interesting to note that a decrease in the anisotropy of the material with increasing mean stress is predicted by the yield condition and is borne out by the experimental results. For large confining stresses, the material ceases to fail preferentially along the plane of weakness.
Inertia Coefficients for Riser Configurations
Authors: Dalton C.
Published: November 2009

Inertia coefficients for arrays of cylinders, such as might be found in risers or conductor pipes, are determined. The method used is theoretical and does not take into account viscous-related phenomena. Values of the inertia coefficient for individual cylinders in three different geometrical arrays are determined using the method of images. It is shown quite vividly the effect the geometry can have on the individual cylinder values.
Criterion for Allowable Lower Ball Joint Angle in Floating Drilling
Authors: Fowler J. R. , Gardner T. N.
Published: November 2009

In drilling from floating vessels, most operators and drilling contractors specify an allowable lower ball joint angle of 3–5 deg for drilling and 1–3 deg for running casing. Presently, no one uses tension in the drill pipe or casing as a factor in setting allowable ball joint angles. The results of the analysis detailed in this paper show that the allowable ball joint angles in use are justified for well depths less than 5000 ft below the ball joint. However, the allowable angle is too high for continual operation for well depths below the ball joint of 10,000 ft or more. The increased drill pipe or casing tension in deeper wells causes high alternating stresses in the drill pipe and high wear rates where the pipe bears against equipment in the ball joint region. The principal conclusion of this paper is that the allowable lower ball joint angle should not be constant, but should vary with the tension in the drill pipe as the well is being drilled.
Dynamic Analysis of Marine Risers With Vortex Excitation
Authors: Nordgren R. P.
Published: November 2009

The basic equations for nonplanar transverse vibrations of marine risers are derived from the theory of elastic rods. A numerical method is developed for solution of the equations by time integration. Spatial discretization is accomplished by a hybrid finite element method. Vortex excitation is modeled by the coupled wake oscillator proposed by Iwan and Blevins. The vortex oscillator equations are integrated numerically in time along with the riser equations. By way of example, several typical riser problems are analyzed including forced vibration and vortex-induced vibration.
Application of an Adaptive Numerical Technique to 3-D Pipeline Problems With Strong Nonlinearities
Authors: Konuk I.
Published: November 2009

Several three-dimensional pipeline problems are used to illustrate a general pipeline and riser model with twist. A continuation technique is developed to solve convergence problems. Suitable stiff numerical methods are reviewed for general applications.