bluuebunny/crossref_metadata_2025 huggingface dataset:
Flow patterns, sedimentation and deposit architecture under a hydraulic jump on a non‐eroding bed: defining hydraulic‐jump unit bars
Authors: MACDONALD ROBERT G. , ALEXANDER JAN , BACON JOHN C. , COOKER MARK J.
Published: January 2009

This paper presents results from two flume runs of an ongoing series examining flow structure, sediment transport and deposition in hydraulic jumps. It concludes in the presentation of a model for the development of sedimentary architecture, considered characteristic of a hydraulic jump over a non‐eroding bed. In Run 1, a hydraulic jump was formed in sediment‐free water over the solid plane sloping flume floor. Ultrasonic Doppler velocity profilers recorded the flow structure within the hydraulic jump in fine detail. Run 2 had identical initial flow conditions and a near‐steady addition of sand, which formed beds with two distinct characteristics: a laterally extensive, basal, wedge‐shaped massive sand bed overlain by cross‐laminated sand beds. Each cross‐laminated bed recorded the initiation and growth of a single surface feature, here defined as a hydraulic‐jump unit bar. A small massive sand mound formed on the flume floor and grew upstream and downstream without migrating to form a unit bar. In the upstream portion of the unit bar, sand finer than the bulk load formed a set of laminae dipping upstream. This set passed downstream through the small volume of massive sand into a foreset, which was initially relatively coarse‐grained and became finer‐grained downstream. This downstream‐fining coincided with cessation of the growth of the upstream‐dipping cross‐set. At intervals, a new bed feature developed above and upstream of the preceding hydraulic‐jump unit bar and grew in the same way, with the foreset climbing the older unit bar. The composite architecture of the superimposed unit bars formed a fanning, climbing coset above the massive wedge, defined as one unit: a hydraulic‐jump bar complex.
Bromide distribution characteristics of different Zechstein 2 rock salt sequences of the Southern Permian Basin: a comparison between bedded and domal salts
Authors: KÜSTER YVONNE , SCHRAMM MICHAEL , BORNEMANN OTTO , LEISS BERND
Published: January 2009

The bromide profile of the bedded Zechstein 2 rock salts in the Southern Permian Basin is characterized by a continuous increase in the bromide contents from base to top, indicating progressive evaporation of sea water. Former studies have suggested that the bromide distribution in domal salts is more irregular, raising such questions as whether there is a causal relationship between bromide distribution and deformation‐related processes or whether various halite types with different primary bromide contents account for such irregularities. In this study, the bromide distribution of a defined stratigraphic section (Hauptsalz) of the Zechstein 2 was investigated in three salt deposits, with bedded salt (Teutschenthal) compared with domal salts (Morsleben and Gorleben). Furthermore, two different halite types (Kristallbrocken, matrix) were distinguished during sampling. Comparison between the locations reveals that: (i) the characteristic trend of the bromide profile was generally preserved in both the bedded and the more intensely deformed domal salts; (ii) the dispersion of bromide contents along the running average curve is lower in domal salt, especially in the lower half of the Hauptsalz; and (iii) the Kristallbrocken are absent in the lower half of the Hauptsalz of Morsleben and Gorleben. The absence of the Kristallbrocken and the lower dispersion of the bromide contents in the domal salts are clear indications for the influence of salt migration‐related processes on the bromide distribution characteristics. It shows that these processes are associated with a redistribution of bromide, which eventually results in a homogenization of the originally varying bromide contents. On the other hand, preservation of the characteristic trend in the bromide profiles indicates that large‐scale brecciation, folding processes or circulating bromide‐rich fluids played only a minor role during the formation of the salt domes. Selective sampling of the Kristallbrocken and matrix halite displays a disparity in bromide content that is not consistent between the studied locations. These specific phenomena might be related to different depositional locations in the Zechstein Basin or to post‐depositional processes.
Salt shield: intracellular salts provide cellular protection against ionizing radiation in the halophilic archaeon, Halobacterium salinarum NRC‐1
Authors: Kish A. , Kirkali G. , Robinson C. , Rosenblatt R. , Jaruga P. , Dizdaroglu M. , DiRuggiero J.
Published: January 2009

The halophilic archaeon Halobacterium salinarum NRC‐1 was used as a model system to investigate cellular damage induced by exposure to high doses of ionizing radiation (IR). Oxidative damages are the main lesions from IR and result from free radicals production via radiolysis of water. This is the first study to quantify DNA base modification in a prokaryote, revealing a direct relationship between yield of DNA lesions and IR dose. Most importantly, our data demonstrate the significance of DNA radiation damage other than strand breaks on cell survival. We also report the first in vivo evidence of reactive oxygen species scavenging by intracellular halides in H. salinarum NRC‐1, resulting in increased protection against nucleotide modification and carbonylation of protein residues. Bromide ions, which are highly reactive with hydroxyl radicals, provided the greatest protection to cellular macromolecules. Modified DNA bases were repaired in 2 h post irradiation, indicating effective DNA repair systems. In addition, measurements of H. salinarum NRC‐1 cell interior revealed a high Mn/Fe ratio similar to that of Deinococcus radiodurans and other radiation‐resistant microorganisms, which has been shown to provide a measure of protection for proteins against oxidative damage. The work presented here supports previous studies showing that radiation resistance is the product of mechanisms for cellular protection and detoxification, as well as for the repair of oxidative damage to cellular macromolecules. The finding that not only Mn/Fe but also the presence of halides can decrease the oxidative damage to DNA and proteins emphasizes the significance of the intracellular milieu in determining microbial radiation resistance.
Relationship between post‐occlusive forearm skin reactive hyperaemia and vascular disease in patients with Type 2 diabetes—a novel index for detecting micro‐ and macrovascular dysfunction using laser Doppler flowmetry
Authors: Yamamoto‐Suganuma R. , Aso Y.
Published: January 2009

Aims  To investigate the relationship between the novel post‐occlusive forearm skin reactive hyperaemia (PORH) index and macro‐ and microangiopathy by comparing it with traditional indices and a morphological analysis of skin blood flow after ischaemia.

Methods  We studied 20 control subjects and 104 patients with Type 2 diabetes. Cutaneous blood flow (flux) in response to 5‐min arterial occlusion in the forearm was measured using laser Doppler flowmetry. We defined the PORH index as the ratio of the area under the curve (AUC) 1 min after the release of the cuff relative to the AUC of a 1‐min period before cuff inflation. The flux in response to arterial occlusion was divided morphologically into three patterns. Brachial‐ankle pulse wave velocity (baPWV) was measured.

Results  The PORH index was markedly lower in patients with diabetes than in control subjects. The PORH index correlated negatively with urinary albumin, peroneal motor nerve conduction velocity, and baPWV in the patients with diabetes. The PORH index, but not the morphological analysis, was an independent determinant of cardiovascular disease in patients with diabetes.

Conclusions  The PORH index may be the most sensitive indicator of micro‐ and macrovascular disease of the various measures of PORH in patients with Type 2 diabetes.
Haemodialysis is associated with changes in cutaneous microcirculation in diabetes mellitus
Authors: Beckert S. , Sundermann K. , Wolf S. , Königsrainer A. , Coerper S.
Published: January 2009

Aims  To examine the cutaneous microcirculation on the dorsum of the foot before, during and after haemodialysis in diabetic and non‐diabetic patients.

Methods  Fourteen age‐matched patients (seven diabetic, seven non‐diabetic) without active foot ulceration were studied. Cutaneous microcirculation was assessed using a micro‐lightguide spectrophotometer to measure venous oxygen saturation and relative blood flow determined at two tissue depths: 2 and 6 mm. Cumulative relative changes of each parameter during haemodialysis were calculated as area under the curve. Differences between and within the groups were calculated by Mann–Whitney U‐test and anova following post hoc testing, respectively.

Results  At baseline, relative blood flow at 6 mm tissue depth was significantly greater in diabetic patients (P = 0.048). Thirty minutes after the end of dialysis, relative blood flow at 2 and 6 mm tissue depth was significantly higher in non‐diabetic patients (P = 0.048 and P = 0.001). Mean cumulative relative changes in venous oxygen saturation and relative blood flow at 2 mm as well as 6 mm tissue depth were positive for non‐diabetic subjects and negative for diabetic patients.

Conclusions  Haemodialysis is associated with changes in cutaneous microcirculation, which differ between people with and without diabetes. In those without diabetes, we found an increase in blood flow during haemodialysis, whereas blood flow was reduced in diabetic patients. This may be the result of abnormal vasomotor regulation due to distal neuropathy.
Agreement between an isolated rater and a group of raters
Authors: Vanbelle S. , Albert A.
Published: January 2009

The agreement between two raters judging items on a categorical scale is traditionally assessed by Cohen's kappa coefficient. We introduce a new coefficient for quantifying the degree of agreement between an isolated rater and a group of raters on a nominal or ordinal scale. The group of raters is regarded as a whole, a reference or gold‐standard group with its own heterogeneity. The coefficient, defined on a population‐based model, requires a specific definition of the concept of perfect agreement. It has the same properties as Cohen's kappa coefficient and reduces to the latter when there is only one rater in the group. The new approach overcomes the problem of consensus within the group of raters and generalizes Schouten's index. The method is illustrated on published syphilis data and on data collected from a study assessing the ability of medical students in diagnostic reasoning when compared with expert knowledge.
Shrinkage Inverse Regression Estimation for Model-Free Variable Selection
Authors: Bondell Howard D. , Li Lexin
Published: January 2009

The family of inverse regression estimators that was recently proposed by Cook and Ni has proven effective in dimension reduction by transforming the high dimensional predictor vector to its low dimensional projections. We propose a general shrinkage estimation strategy for the entire inverse regression estimation family that is capable of simultaneous dimension reduction and variable selection. We demonstrate that the new estimators achieve consistency in variable selection without requiring any traditional model, meanwhile retaining the root n estimation consistency of the dimension reduction basis. We also show the effectiveness of the new estimators through both simulation and real data analysis.
Impact of a modified directly administered antiretroviral treatment intervention on virological outcome in HIV‐infected patients treated in Burkina Faso and Mali
Authors: Pirkle CM , Boileau C , Nguyen V‐K , Machouf N , Ag‐Aboubacrine S , Niamba PA , Drabo J , Koala S , Tremblay C , Rashed S
Published: January 2009

Objective

This study explores whether viral load measurements can be used in resource‐limited settings to target those in need of adherence assistance. It was hypothesized that high plasma viral loads (pVLs) (≥500 HIV‐1 RNA copies/mL) were the result of poor antiretroviral therapy adherence and amenable to improvement with adherence assistance.

Design

A single‐arm, multicentre pilot study was conducted from November 2003 to March 2004 on 606 treatment‐experienced patients who had initiated an antiretroviral regimen in Mali and Burkina Faso ≥6 months before study enrolment. In these patients, those whose pVL was ≥500 copies/mL were offered 1 month of modified directly administered antiretroviral treatment (mDAART) with weekly follow‐up visits from pharmacists or adherence counsellors.

Methods

An adherence questionnaire was given to all cohort patients and viral load was used to screen for patients with ≥500 copies/mL. mDAART participants included cohort patients with ≥500 copies/mL, who completed the adherence questionnaire. Genotypic analyses were conducted on samples taken prior to and after the intervention. The intervention was considered effective when there was a decrease of ≥1 log10 in pVL.

Results

mDAART was effective in over one‐third of the intervention participants, while in two‐thirds no decrease in pVL was observed. The majority of mDAART participants had major resistance mutations.

Conclusions

pVL measurement was useful to identify patients who needed adherence assistance. However, because it was performed ≥6 months after starting treatment, mDAART came too late for most participants, as they had already developed important resistance mutations that might have been avoided with better laboratory monitoring.
Migraine is a Risk Factor for Hypertensive Disorders in Pregnancy: A Prospective Cohort Study
Authors: Facchinetti F , Allais G , Nappi RE , D'Amico R , Marozio L , Bertozzi L , Ornati A , Benedetto C
Published: January 2009

The aim was to assess whether women suffering from migraine are at higher risk of developing hypertensive disorders in pregnancy. In a prospective cohort study, performed at antenatal clinics in three maternity units in Northern Italy, 702 normotensive women with singleton pregnancy at 11–16 weeks' gestation were enrolled. Women with a history of hypertensive disorders in pregnancy or presenting chronic hypertension were excluded. The presence of migraine was investigated according to International Headache Society criteria. The main outcome measure was the onset of hypertension in pregnancy, defined as the occurrence of either gestational hypertension or preeclampsia. Two hundred and seventy women (38.5%) were diagnosed with migraine. The majority (68.1%) suffered from migraine without aura. The risk of developing hypertensive disorders in pregnancy was higher in migraineurs (9.1%) compared with non-migraineurs (3.1%) [odds ratio (OR) adjusted for age, family history of hypertension and smoking 2.85, 95% confidence interval (CI) 1.40, 5.81]. Women with migraine also showed a trend to increased risk for low birth weight infants with respect to women without migraine (OR 1.97, 95% CI 0.98, 3.98). Women with migraine are to be considered at increased risk of developing hypertensive disorders in pregnancy. The diagnosis of primary headaches should be taken into account at antenatal examination.
Superficial basal cell carcinoma treated with imiquimod 5% topical cream for a 4‐week period: a case series
Authors: Ruiz‐Villaverde R , Sánchez‐Cano D , Burkhardt‐Pérez P
Published: January 2009

Basal cell carcinoma (BCC) is a malignant cutaneous neoplasm with a tendency to spread locally and with several clinical and histological subsets. We studied 82 patients with a clinical diagnosis of superficial BCC on different anatomical locations, to whom imiquimod 5% cream was administered on a low‐frequency regime (three times a week for 4 weeks), and who were followed up 2 years after completion of treatment. Clinical clearance rate at 1 and 2 years were 89% and 85%, respectively. We conclude that imiquimod seems to be an appropriate therapeutic alternative for the treatment of superficial BCC in patients with associated comorbidities.

Conflicts of interest

None declared
Shared and disorder‐specific prefrontal abnormalities in boys with pure attention‐deficit/hyperactivity disorder compared to boys with pure CD during interference inhibition and attention allocation
Authors: Rubia Katya , Halari Rozmin , Smith Anna B. , Mohammad Majeed , Scott Stephen , Brammer Michael J.
Published: January 2009

Background:  Inhibitory and attention deficits have been suggested to be shared problems of disruptive behaviour disorders. Patients with attention deficit hyperactivity disorder (ADHD) and patients with conduct disorder (CD) show deficits in tasks of attention allocation and interference inhibition. However, functional magnetic resonance imaging (fMRI) of inhibitory and attention control has only been investigated in patients with ADHD, including comorbidity with CD, finding fronto‐striatal and temporo‐parietal dysfunction. This study investigates differences and commonalities in functional neural networks mediating interference inhibition and attention allocation between medication‐naïve children and adolescents with pure CD and those with pure ADHD.

Methods:  Event‐related fMRI was used to compare brain activation of 13 boys with non‐comorbid CD, 20 boys with non‐comorbid ADHD and 20 healthy comparison boys during a Simon task that measures interference inhibition and controls for attention allocation, thus tapping into interference inhibition and selective attention networks.

Results:  During interference inhibition, both patient groups shared reduced activation compared to controls in right superior temporal lobe and in predominantly right precuneus. During the oddball condition, both patient groups showed reduced activation compared to healthy control children in right medial prefrontal lobe. However, only ADHD patients showed a disorder‐specific under‐activation compared to the other two groups in an extensive activation cluster in left inferior prefrontal cortex.

Conclusions:  This study shows shared dysfunction in both patients groups in right hemispheric temporal and parietal brain regions during interference inhibition and in right dorsolateral prefrontal cortex during attention allocation. Ventrolateral prefrontal dysfunction, however, was specific to ADHD and not observed in patients with CD in the context of attention allocation. The findings suggest that the typically reduced functional activation in patients with ADHD in ventrolateral prefrontal cortex may be specific to the disorder, at least when compared to patients with CD.
The Inefficiencies of Regionalised Milk Quota Trade
Authors: Hennessy Thia , Shrestha Shailesh , Shalloo Laurence , Wallace Michael
Published: January 2009

This paper estimates the inefficiencies associated with the regionalisation of the milk quota trade. An optimisation model is developed to estimate the economic value of quota. Quota values are aggregated to derive quota sale and purchase curves under two scenarios: first, where quotas can be traded nationally and second, where the trade of quota is regionally restricted. Quota trade is simulated and the consequent effects on supplier structure estimated. Through the derivation of sectoral cumulative cost curves it is possible to estimate the impact of regionalising quota trade on sector efficiency. The model is solved using National Farm Survey data from Ireland and the inefficiencies of regionalised quota trade in Ireland are estimated at €27 million. The paper concludes by discussing the implications of restricted quota trade, especially in the context of eventual quota removal.
Lack of evidence of transfusion transmission of Creutzfeldt‐Jakob disease in a US surveillance study
Authors: Dorsey Kerri , Zou Shimian , Schonberger Lawrence B. , Sullivan Marian , Kessler Debra , Notari Edward , Fang Chyang T. , Dodd Roger Y.
Published: January 2009

BACKGROUND: Since 2004, several reported transfusion transmissions of variant Creutzfeldt‐Jakob disease (vCJD) in the United Kingdom have reawakened concerns about the possible risk of similar transmissions of nonvariant or classic forms of CJD.

STUDY DESIGN AND METHODS: Patients with a CJD diagnosis and a history of donating blood were reported to the study coordinator. Through review of blood distribution and hospital records, the recipients of blood components from these donors were identified. We then determined each recipient's vital status and, if deceased, the cause(s) of death identified by matching the recipient's personal identifiers with the Centers for Disease Control and Prevention's National Death Index database. We conducted such searches after recipients were enrolled in this study and annually thereafter for those who remained alive.

RESULTS: The study included a total of 36 blood donors who subsequently developed CJD and 436 recipients. Through 2006, 91 of these recipients were still alive, 329 were deceased, and 16 were lost to follow‐up. After transfusion, these three groups had survived a total of 2096.0 person‐years. A total of 144 recipients survived 5 years or longer after transfusion and 68 of them had received blood donated 60 or fewer months before the onset of CJD in the donor. We identified no recipient with CJD.

CONCLUSIONS: The current results of this large, ongoing lookback study show no evidence of transfusion transmission of CJD. They reinforce the conclusion that the risk, if any, of transfusion transmission of prion disease by CJD donors is significantly lower than the comparable risk of such transmission by vCJD donors.
Supplementary feeding with fortified spread among moderately underweight 6–18‐month‐old rural Malawian children
Authors: Phuka John , Thakwalakwa Chrissie , Maleta Kenneth , Cheung Yin Bun , Briend André , Manary Mark , Ashorn Per
Published: January 2009

We aimed to analyse growth and recovery from undernutrition among moderately underweight ambulatory children receiving micronutrient‐fortified maize–soy flour (Likuni Phala, LP) or ready‐to‐use fortified spread (FS) supplementary diet. One hundred and seventy‐six 6–18‐month‐old individuals were randomized to receive 500 g LP or 350 g FS weekly for 12 weeks. Baseline and end of intervention measurements were used to calculate anthropometric gains and recovery from underweight, wasting and stunting. Mean weight‐for‐age increased by 0.22 (95% CI 0.07–0.37) and 0.28 (0.18–0.40) Z‐score units in the LP and FS groups respectively. Comparable increase for mean weight‐for‐length was 0.39 (0.20–0.57) and 0.52 (0.38–0.65) Z‐score units. Recovery from underweight and wasting was 20% and 93% in LP group and 16% and 75% in FS group. Few individuals recovered from stunting and mean length‐for‐age was not markedly changed. There were no statistically significant differences between the outcomes in the two intervention groups. In a poor food‐security setting, underweight infants and children receiving supplementary feeding for 12 weeks with ready‐to‐use FS or maize–soy flour porridge show similar recovery from moderate wasting and underweight. Neither intervention, if limited to a 12‐week duration, appears to have significant impact on the process of linear growth or stunting.
QT Dispersion and Heart Rate Predict the Risk of Sudden Unexpected Cardiac Death in Men: The Manitoba Follow‐up Study
Authors: Edward Cuddy Thomas , Halli Priyanka S. , Tate Robert B.
Published: January 2009

As many as half of all sudden cardiac deaths are unexpected, with no preceding symptoms or signs of cardiac problems. Since 1948, the Manitoba Follow‐up Study has prospectively recorded routine medical information and resting electrocardiographic (ECG) findings from a cohort of 3983 men. During 58 years of follow‐up, 180 men experienced sudden unexpected cardiac death (SUCD). Heart rate, the longest QT interval, the shortest QT interval, and their difference and QT dispersion (QTD) on ECGs recorded prior to SUCD and 5 years and 10 years earlier were compared with QT intervals on ECGs of age‐matched controls. QTD and heart rate each were significantly (P<.01) and independently associated with increased risk for SUCD. Only primary prevention can reduce the risk for SUCD. Hence, this relationship between QTD and heart rate and SUCD emphasizes the importance of longitudinal noninvasive QT measurements on routine ECGs in healthy men.
LA‐(MC)‐ICP‐MS Trends in 2006 and 2007 with Particular Emphasis on Measurement Uncertainties
Authors: Sylvester Paul J.
Published: January 2009

Research in 2006 and 2007 dealing with laser ablation‐(multicollector)‐inductively coupled plasma‐mass spectrometry, LA‐(MC)‐ICP‐MS, involved studies concerned with optimising the technique itself, as well as applying the method to a variety of problems in the Earth sciences. The causes of elemental and isotopic fractionation produced during laser ablation continues to be of considerable interest, with evidence mounting that processes occurring both at the ablation site and in the argon plasma of the ICP are culpable. There is growing excitement in the use of femtosecond lasers for LA‐(MC)‐ICP‐MS, with the hope that they reduce or eliminate melting and non‐congruent volatilisation at the ablation site and thus approach stoichiometric sampling. Ablation chamber design emerged as a serious concern, particularly with respect to achieving the rapid washout needed for fine‐scale compositional mapping of geological objects. LA‐MC‐ICP‐MS provided data for a wide range of isotopic systems, especially hafnium, but also B, S, Mg, Cu, Fe, Sr, Nd, Pb and U. Measurement uncertainties in LA‐ICP‐MS were discussed by several researchers, and are critically reviewed here ‐ total uncertainties for trace element concentration measurements of silicates including errors on the calibration values of common reference materials are ∼10% (95% confidence limits), though the precision of individual spot measurements (50 to 100 μm) is much better, ∼1% RSD, using a 193 nm laser and a sector field‐ICP‐MS. LA‐ICP‐MS U‐Pb ages for zircon and other U‐rich accessory phases are claimed by most geoanalysts to have 2s uncertainties of ∼0.7 and 1.3% respectively but the actual accuracy of the method is probably only as good as ∼2% (2s), when uncertainties associated with laser‐induced Pb/U fractionation are included.
PSYCHOTHERAPY AND THE ‘PLAGUE’: SOME CONTRIBUTIONS TO THE UNDERSTANDING OF A RECURRING THREAT
Authors: Briant Michael
Published: January 2009

abstract  Violence perpetrated in the name of religious or moral regeneration is neither new nor peculiar to any particular creed or ideology. It is an ancient phenomenon, the history and psychology of which have been extensively studied, especially in Northern and Central Europe.

The paper considers a case history of one major manifestation of it in the twentieth century, and related attempts to conceptualize key problems it raises. A link is made with the more recent research of James Gilligan, a leading modern theorist of violence. This wider perspective is needed if we are to understand and combat the re‐emergence of the phenomenon today.
PSYCHOTHERAPY AND RESEARCH: A RELATION THAT NEEDS TO BE REINVENTED
Authors: Vanheule Stijn
Published: January 2009

abstract  In this paper I question whether the randomized controlled trial (RCT) and the evidence‐based medicine model are well suited for psychotherapy research. First I discuss general characteristics of the randomized controlled trial and argue that, given a number of incompatibilities with the discipline of psychotherapy, these trials tend to provide us with data that have limited validity. The methodological objections I raise are important as the treatment protocols produced within the context of randomized controlled trials tend to be forced upon clinical practice in uncritical ways. On the other hand, I argue that systematic research is relevant for psychotherapy. If research is designed to address concerns arising from clinical practice – in particular, the far‐reaching complexity of the therapeutic encounter – it can be a powerful tool for further developing our discipline.
Uncertainty propagation in a London flood simulation
Authors: Golding B.W.
Published: January 2009

Following recent costly flood events in the United Kingdom, there is considerable societal and political pressure to reduce flooding and improve warnings. In response to this, the Flood Risk Management Research Consortium (FRMRC) has been created to investigate the potential of several areas of existing research to be brought into operational use. In this paper, the estimation of flood impact and probability is analysed and illustrated with examples from a simulated forecast of a Thames Estuary flood event carried out at a FRMRC workshop. The forecast modelling chain consisted of meteorology, storm surge, estuary hydrodynamics, defence failure and inundation. The workshop concluded that end‐to‐end propagation of probability was feasible in an integrated real‐time flood forecasting system, and that the basis of such a system had been demonstrated.
Estimation of Unknown Boundary Heat Flux in Laminar Circular Pipe Flow Using Functional Optimization Approach: Effects of Reynolds Number
Authors: Ding Peng , Tao Wen-Quan
Published: January 2009

An inverse forced convection problem was studied in this paper. The unknown space-dependent heat flux at the outer boundary of a circular pipe was identified from the temperature measurements within the flow using the algorithm based on an improved conjugate gradient method, which is a combination of the modified inverse algorithm proposed by Ozisik et al. (Huang and Ozisik, 1992, “Inverse Problem of Determining Unknown Wall Heat Flux in Laminar Flow Through a Parallel Plate Duct,” Numer. Heat Transfer, Part A 21, pp. 2615–2618) and the general inverse algorithm based on the conjugate gradient method. The effects of the convection intensity, the number of thermocouples, the location of the thermocouples, and the measurement error on the performance of the modified inverse algorithm method and the improved inverse algorithm were studied thoroughly through three examples. It is shown that the improved inverse algorithm can greatly improve the solution accuracy in the entire computation domain. The accuracy and stability of both the modified inverse algorithm method and the improved inverse algorithm are strongly influenced by the Reynolds number and the shape of the unknown heat flux. Those functions, which contain more high-frequency components of Fourier series, are more sensitive to the increase in the Reynolds number.
Effect of Coal Type on Emission Characteristics of Alkali Metal Compounds in Particulate Matters
Authors: Takuwa Tsuyoshi , Naruse Ichiro
Published: January 2009

Some metal compounds in coal vaporize and form fumes during combustion. The fumes are generally exhausted through the flue gas. For coal-fired combined power generation systems such as pressurized fluidized bed combustion (PFBC), hot vapors may contact with the surfaces of gas-turbine blades. As this contact of the hot vapors with the surface has corrosive effect, it is necessary to control the formation of those fumes, which mainly contain alkali metal compounds. In this paper, the evolution behavior of alkali metal compounds, especially for sodium compounds, has been studied, using an electrically heated drop tube furnace with a low-pressure impactor. The main objective in this study is to elucidate the conditions and the possible mechanisms to form alkali metal compounds in particulate matter during combustion. Two types of coal with different sodium content were tested, where the coal conversion characteristics were established. Furthermore, the evolution and inclusion of sodium compounds into the sub-micron particles were studied in relation to the particle size distribution formed and sodium fraction distribution in the collected fine particulates. The study proved that the evolution and inclusion of sodium in the sub-micron particles depended on function of type of coal via its composition and the form by which sodium compounds existed in coal. The reaction-controlled mechanism and heterogeneous condensation via chemical reactions during combustion affected the inclusion of sodium in the sub-micron particles. In the coarse particles of above about 0.5 μm, reaction that formed those particles was mainly via gas film diffusion surrounding the particle.
Experimental Research and Analysis on Self-Desulfuration Efficiency of Coal in Circulating Fluidized Combustor
Authors: Wang Zhiwei
Published: January 2009

The SO2 emission is less than the theoretical value without additional limestone put in a circulating fluidized bed (CFB) combustor because of the self-desulfurization ability of calcium-based minerals in coal ash. The modeling and experiment on limestone sulfur retention should consider the self-desulfurization of coal ash. The self-desulfurization performance of some coal (18 kinds of coal) are researched and analyzed by the 1MWth CFB combustor in order to evaluate the limestone desulfurization performance. The experimental results show that the self-desulfurization efficiency decreases with the temperature increasing. The self-desulfurization difference exits between different types of coal and has effect on the sulfur retention with additional limestone. Through the experimental result of 18 coals, simple equations of the self-desulfurization efficiency based on the total sulfur and the combustible sulfur are proposed. The self-desulfurization efficiency based on the combustible sulfur is between 40–40%. For high incombustible sulfur fraction in coal, the self-desulfurization efficiency and the sulfur retention of limestone is very high.
Horizontal Pressure Fluctuation in Bubbling Fluidized Bed
Authors: Walle´n Vesa V.
Published: January 2009

Pressure measurements were conducted in a two-dimensional hot atmospheric bubbling fluidized bed reactor in the laboratory of Energy and Process Engineering at Tampere University of Technology. A set of six fast pressure transducers was used to detect the rapid pressure fluctuations inside the bubbling bed of the reactor. These pressure transducers were placed both vertically and horizontally into the reactor. From these measurements it was found that the vertical pressure fluctuation took place at the same time at different levels of the bed. Also the same fluctuation could be seen under the air distributor. The horizontal pressure fluctuation was found to vary both by place and time. At the bottom part of the bed the highest pressure peaks was found at centre of the bed. Most of the time there was a pressure gradient the highest pressure being in the centre of the bed. This gradient creates horizontal flow of gases from middle to the sides. The velocity of this flow varies with the size of the pressure gradient. The opposite effect can be found in the upper part of the bed. The highest pressure was no more in the middle part of the bed. Instead, it was found to be between the centre of the bed and left and right walls. The pressure was low at the walls but also rather low at the middle of the bed. There must be flow towards the walls and to the centre axis. These pressure fluctuations can provide an explanation for the well-known “wandering plume” effect. They can also give a tool to better describe the mixing inside a bubbling fluidized bed. This kind of tool is needed when biomass combustion is modelled in bubbling fluidized bed.
Combustion of Waste Fuels in Sound-Assisted Fluidized Beds
Authors: Cammarota A. , Chirone R. , Urciuolo M.
Published: January 2009

In the present work, sound-assisted fluidized bed combustion has been investigated by means of a 41mm laboratory scale apparatus fed with combustible powders of different fuels: a tyre derived fuel, a lignite and a petroleum coke. The experiments aim at studying the effect of sound intensity and frequency on carbon conversion of elutriable fines generally produced during fluidized bed combustion of solid fuels. The effectiveness of sound application is evaluated in terms of effects on bed carbon loading, carbon elutriation rate, combustion time and degree of conversion of fixed carbon. Experimental data prove that application of acoustic fields of appropriate intensity and frequency may: increase bed carbon loading and combustion time, reduce elutriation of carbon fines and increase efficiency of fixed carbon conversion. The effects are different for each fuel depending on its characteristics. A simplified model of sound-assisted fluidized bed has been developed. The model has been validated by comparing the experimental optimum intensity and frequency with calculated values of minimum intensity and optimum frequency. The present formulation of the model is useful for the design of the acoustic field to be used in sound-assisted fluidized bed combustors.
Optimizing the Fuel Reactor for Chemical Looping Combustion
Authors: Ada´nez Juan , Garci´a-Labiano Francisco , de Diego Luis F. , Plata Ainhoa , Celaya Javier , Gaya´n Pilar , Abad Alberto
Published: January 2009

A mathematical model for a bubbling fluidized bed has been developed to optimize the performance of the fuel reactor in chemical looping combustion systems. This model considers both the hydrodynamic of the fluidized bed (dense bed and freeboard) and the kinetics of the oxygen carrier reduction. Although the model is valid for any of the possible oxygen carriers and fuels, the present work has been focused in the use of a carrier, CuO-SiO2, and CH4 as fuel. The shrinking core model has been used to define the particle behavior during their reduction. The simulation of the fuel reactor under different operating conditions was carried out to set the operating conditions and optimize the process. The effect of different design or operating variables as the bed height, the oxygen carrier/fuel ratio, and the gas throughput was analyzed. Finally, a sensitivity analysis to the solid reactivity, the bubble diameter, and to the gas/solid contact efficiency in the freeboard was done. At vigorous fluidization, solid present in the freeboard can strongly contribute to the gas conversion in the fuel reactor. However, the gas/solid contact efficiency in this zone must be determined for each particular case.
The Gasification of Sewage Sludge in Bubbling Fluidized Beds
Authors: Harris A. T. , Scott S. A. , Dennis J. S. , Hayhurst A. N. , Davidson J. F.
Published: January 2009

This paper gives the first measurements from a project investigating the gasification of dried sewage sludge in a laboratory scale, bubbling fluidized bed at atmospheric pressure. The aim of the work was to examine the reactions occurring in a fluidized bed gasifier rather than simply treat the reactor as a ‘black box’. Experiments were performed to investigate the rates of drying, devolatilisation, gasification and combustion. Thermogravimetric analysis, as well as batch fluidized bed experiments using mechanically dewatered, dried and pelletised municipal sewage sludges from different regions in the UK were performed. A comparison was made between the different samples of sludge and a low rank coal and softwood biomass. A distributed activation energy model (DAEM) for interpreting the kinetics of devolatilisation was also investigated. The model was able to reduce the results from several TGA experiments to a single curve characterised by a single parameter, the pre-exponential factor, A.
Fireside Deposit Formation in Biomass Fired FBC: A Comparison Between Tests Performed in Three Significantly Different Sized Combustors
Authors: Skrifvars Bengt-Johan , Yrjas Patrik , Hupa Mikko , Aho Martti , Silvennoinen Jaani , Etela¨aho Risto , Kouki Juha , Saari Kari
Published: January 2009

This paper deals with the prediction of ash related problems in fluidized bed boilers during co-firing of various bio-fuels. A study was performed where the slagging and fouling behavior was monitored in three different sized bubbling fluidized bed combustors, a 20 kW semi-pilot reactor, a 2 MW pilot-scale device and a 105 MW full-scale boiler. The aim of the study was to learn about how well slagging and fouling in a small-scale device compares to a full-scale boiler and to see how well the slagging and fouling can be predicted with a small-scale device. Various types of Scandinavian bio-fuels as well as peat were used both separately and mixed. From all three devices ash and deposit samples were collected during as uniform and stable conditions as possible. The fuels used in the three devices during the test campaigns were carefully chosen so that they would be as similar as possible. Bed, furnace and flue gas temperatures were monitored as well as flue gas emissions. The fuels, ashes and deposits were analyzed on their main components and deposition rates were calculated based on the deposit measurements. These data were finally used for assessing the slagging and fouling propensity of the fired fuel. The paper compares and discusses the results from the three different size classes.
CFD Based Ash Deposition Prediction in a BFB Firing Mixtures of Peat and Forest Residue
Authors: Mueller Christian , Lundmark Dan , Skrifvars Bengt-Johan , Backman Rainer , Zevenhoven Maria , Hupa Mikko
Published: January 2009

Fuels currently used for energy production in thermal power plants are characterized by their huge variety ranging from fossil fuels to biomass and waste. This multitude of fuels offers opportunities to the energy industry and nowadays many power plants do not fire either of these fuels but mixtures of them are burnt. While this procedure may lead to overall economic and environmental advantages it is very demanding for the boiler operators to still meet expectations concerning boiler performance, boiler availability and emission regulations. In the course of this latest trend in boiler operation, ash related operational problems such as slagging, fouling and corrosion are ranking very high on the list of reasons leading to significant reduction of boiler availability. Ash related problems strongly dependent on fuel specific aspects, such as the mineral matter distribution in the fuel, aspects specific to the used combustion technique as well as design aspects unique for the combustion chamber of any operating power plant. The overall goal in combustion related research is therefore the prediction of potential operational problems originating from fuel streams entering the combustion chamber as well as those originating from the design of individual furnaces. In our earlier work we have strongly focused on developing an advanced ash behavior prediction tool for biomass combustion combining computational fluid dynamic calculations (CFD) and advanced fuel analysis. In this paper the tool is applied to analyze the slagging and fouling tendency in a 295 MW bubbling fluidized bed boiler fired with mixtures of peat and forest residue. In addition to the overall deposition prediction this work focuses on details of the models used in the computational fluid dynamic calculations. These include a study on the importance of the accurate description of the fuel feeding system and related to this aspect the advanced description of the bubbling bed with regard to release of primary gas and ash particles from its surface to the freeboard. Evaluation of the predictions comparing simulation results with deposits on the furnace walls show good agreement.
Gas-Mixing in Bubbling Fluidized Bed Combustors: Hydrodynamics and Macromixing Associated With Bubble Bursting at the Bed Surface
Authors: Solimene R. , Marzocchella A. , Salatino P. , Ragucci R.
Published: January 2009

Gas-mixing phenomena may play a significant role in fluidized bed combustion of solid fuels. Issues associated with gas mixing include: a) effectiveness of mass transfer between the bubble and the emulsion phases in the bed; b) degree of mixing between segregated gaseous streams in plume-like or bubbly flow in the bottom bed; c) extent of mixing between segregated gaseous pockets/streams in the splashing zone or in the upper freeboard. Among the others, issues b) and c) turn out to be relevant to fluidized bed combustion of high-volatile solid fuels (biomass, RDF, etc.). In this case, the rate of gas mixing often overcomes intrinsic kinetics as the rate-controlling step in volatile matter burn-out, especially under “stratified” combustion conditions. Despite several and significant contributions to the subject, understanding of gas-mixing in bubbling fluidized beds is still poor and calls for additional investigation. The present work aims at investigating gas-mixing in bubbling fluidized bed with specific reference to the above issue c). A laser assisted imaging technique has been used to characterize the hydrodynamic patterns associated with the bursting of either isolated bubbles or couples of closely time-delayed bubbles at the surface of a fluidized bed. Quantitative image analysis procedures were exploited in order to assess parameters defining the general fluid-dynamic behaviour and macromixing of the bubble-generated gas pockets with the mainstream gas. The formation of toroidal flow structures upon bubble bursting is highlighted in the case of isolated bubbles. The toroidal pockets entrain mainstream gas and grow accordingly while rising along the splash zone. Toroidal flow structures are observed also in the case of couples of closely time-delayed bubbles, but interference between leading and trailing pockets leads to more complex structures characterized by multiple incoherent eddies. The relevance of macromixing to volatile matter burning under conditions of stratified fluidized bed combustion is assessed and discussed.
Control of Ash-Related Operational Problems in BFB Combustion of Biofuels and Waste
Authors: Enestam Sonja H. , Fabritius Marko K. , Hulkkonen Seppo K. , Ro¨ppa¨nen Jukka T.
Published: January 2009

When moving towards CO2 neutral bio fuels and waste derived fuels, new challenges are set for combustion facilities and technical boiler solutions. A common feature for both bio- and waste fuels is a big variety in composition, often high levels of alkali metals, chlorine and moisture which make these fuels difficult to burn in facilities designed for conventional fuels such as coal, peat and wood. The problems that might occur due to high alkali and chlorine levels in the fuels, are slagging, fouling, corrosion and bed sintering. The Fortum BioMAC BFB boilers are designed especially for difficult, unconventional fuels such as rice husk, olive waste, straw, construction residue, de-inking sludge, etc. The design of each individual boiler is made based on advanced theoretical prediction tools and extensive fuel testing in laboratory and in pilot scale combustion facilities. The theoretical tools consist of a multi-phase multi-component chemical equilibrium model that estimates the slagging/fouling, sintering and corrosion propensity of the fuels/fuel mixtures and of a computational fluid dynamics part. CFD calculations are used to optimize the flow pattern and the temperature of the boiler in order to avoid hot temperatures in the vicinity of refractory linings and cooled surfaces. The chemical equilibrium calculations predict the melting behavior of the fuel ash, which is used as an indicator for the placement of the superheaters. The bottom ash removal is controlled for efficient removal of coarse material, screening and recirculation. The ash related problems of important bio and waste fuels, the analytical procedure of the evaluation of the usability of the fuels and the adaptation of the boiler design are discussed in the paper.