bluuebunny/crossref_metadata_2025 huggingface dataset:
MAPPING AND CLASSIFYING FLOW UNITS IN THE UPPER PART OF THE MID‐CRETACEOUS SARVAK FORMATION (WESTERN DEZFUL EMBAYMENT, SW IRAN) BASED ON A DETEMINATION OF RESERVOIR ROCK TYPES
Authors: Beiranvand B. , Ahmadi A. , Sharafodin M.
Published: October 2007

The mid‐Cretaceous Sarvak Formation, the second‐most important reservoir unit in Iran, is composed mainly of grain‐supported carbonates. For the purposes of this study, flow units in the upper part of the formation were identified, mapped and classified as part of an integrated reservoir characterization study at a giant oilfield in SW Iran. Pore types and geometries, pore‐scale diagenetic history and core‐scale depositional attributes were logged using conventional petrographic and lithological methods. The resulting data were combined with core descriptions, mercury‐injection capillary pressure data, and wireline log and geophysical data to identify five reservoir rock types: (i) highly oil‐stained, grain‐supported carbonates, including patch reef and barrier complex deposits with high porosities and permeabilities; (ii) leeward and seaward shoal deposits including grain‐supported packstones and skeletal wackestones with high porosities and permeabilities; (iii) dominantly mud‐supported lagoonal and open‐marine facies with fair porosity and permeability; (iv) grain‐supported but highly cemented facies which had poor reservoir characteristics; and (v) calcareous shales and shaly limestones with no reservoir quality.

Based on the reservoir rock types, eight flow units were recognised. Subsequently, four reservoir zones were defined based on these flow units at a field scale.

This study has contributed to our understanding of flow units in this complex carbonate reservoir, and has improved our ability to characterize and model the architecture of the reservoir from pore to core to field scale.
QUANTITATIVE ESTIMATES OF OIL LOSSES DURING MIGRATION, PART I: THE SATURATION OF PATHWAYS IN CARRIER BEDS
Authors: Luo X. R. , Zhou B. , Zhao S. X. , Zhang F. Q. , Vasseur G.
Published: October 2007

Estimates of hydrocarbon losses during migration are critical to petroleum resource assessments based on mass balance calculations. Using knowledge acquired from physical experiments, we conducted numerical experiments to qualitatively simulate migration processes on a basin scale, and we have estimated the proportions of oil lost along different parts of the migration pathway. Between the point where oil is expelled from a source rock and its arrival in a trap, migration pathways were divided into three sections, namely vertical and lateral pathways within the area of the effective source rock (W1), and lateral pathways outside this area (W2).

With reference to the concept of an independent migration unit (IMU), a prism‐shaped domain with square top and bottom faces, the proportion of vertical pathways (Q1) and lateral pathways (Q2) in carrier beds in W1 may be estimated, using parameters obtained in migration experiments. The proportion of oil lost in W2 was obtained by statistical analysis of modelled results. It is found that the loss of oil within W2 decreases rapidly with increasing distance from the contact between W1 and W2.

Relative oil losses in migration pathways were estimated by considering two typical migration models: a sloping rectangular plate model, and a circular synclinal model. Simulation results show that, for sandstone carrier beds at a basin scale, Q2 is one order of magnitude less than Q1, and losses (Q3) in W2 are two orders of magnitude less than those (Q1+ Q2) in W1.
Political Economy of the Asia‐Pacific Free Trade Area: A Dilemma for China
Authors: Sheng Bin
Published: October 2007

The Asia‐Pacific Free Trade Area (FTAAP) has become a topic of focus since the proposal was first raised in 2004. The present paper considers China's policy towards the FTAAP from a political economy perspective by probing the gains, impediments and concerns for China, and makes judgments based on several possible scenarios. The author argues that from an economic perspective, China would benefit from joining the FTAAP both in a static and a dynamic manner because both its main trade partners and trade barriers in export markets are concentrated in the Asia‐Pacific region. However, whether the Chinese Government is likely to support the initiative is largely dependent on certain crucial political and diplomatic elements, including the APEC approach, US‐Chinese relations, quality of treaty, sensitive sectors, competitive proposal of alternative and membership of Chinese Taipei. Therefore, if the Chinese Government cannot ratify the ideology and terms of the initiative, or issues that are central to China's interests are not addressed, the FTAAP will only remain a proposal possessing economic possibility in the long run, without political feasibility in the near term.
Institutional Root Cause of the Irregularity of Social Security Funds in China
Authors: Zheng Bingwen
Published: October 2007

This paper analyzes institutional defects in the Chinese social security system, based on irregularities in social security funds revealed in the Audit Report by the China National Audit Office. The author divides the irregularities into five categories according to the nature of fund use. The results show that the institutional root cause of the irregularities lies in the unreasonable design and operation of the social security system, which currently faces management and institutional risks. This paper argues that simple rhetoric about strengthening regulation and supervision cannot help to reduce illegal practices, or to realize risk control. The only solution is to reform the social security system. Specifically, the Chinese Government should regulate the administrative cost of the social security system, and the behavior of its agencies, through legislation, reform the investment regime to increase rate of return of pension assets, and adjust and reshape the existing social security system, so as to elevate its pooling level.
Classification of Growth Clubs and Convergence: Evidence from Panel Data in China, 1981–2004
Authors: Zou Wei , Zhou Hao
Published: October 2007

This paper uses provincial panel data to examine club convergence in China during 1981–2004. We estimate the province‐specific initial technology level, A(0), and classify the Chinese economy into “developed club” and “underdeveloped club” based on the economic characteristics of A(0), instead of on geographical location. We find significant evidence of conditional convergence across provinces, and that the convergence speed in the developed club is faster than that in the underdeveloped club. We also find that: (i) human capital accumulation contributes more than physical capital does to club convergence; (ii) there is a positive correlation between infrastructure and growth convergence at the national level and within the developed club, while the spillover effect of infrastructure has not been developed in the developing club; and (iii) the effect of economic openness on convergence is tiny, and insignificant across and within clubs.
New Compensation Standard for Land Expropriation in China
Authors: Zou Xiuqing , Oskam Arie J.
Published: October 2007

This paper explores a new compensation standard for use in agricultural land conversion in China during the land‐expropriation process, based on the market value definition. Assuming identical bargaining power between the buyer and the seller, efficient and equitable compensation is obtained through a market transaction and bargaining negotiation mechanism, under the assumpation of a perfect market. From the state‐of‐the‐art viewpoint of land appraising, a practical approximation of the theoretical optimal compensation will provide an effective solution for China, under the current collective‐owned land property rights structure.
Extrusion of Pea Starch Containing Lysozyme and Determination of Antimicrobial Activity
Authors: Nam S. , Scanlon M.G. , Han J.H. , Izydorczyk M.S.
Published: October 2007

ABSTRACT:  Pea starch, which has inherently good gel strength, was used as the source material for manufacturing a biodegradable and bioactive packaging material. Extrudates containing 99% pea starch and 1% lysozyme were produced under various extrusion conditions (high and low shear screw configurations, 30% to 40% moisture contents, 70 to 150 °C die temperatures). The physical and mechanical properties of the extrudates were determined through various expansion indices, piece and cell wall solid density, compression, and 3‐point bending tests. The expansion of extrudates increased with an increase in die temperature, whereas increasing moisture content had the opposite effect. Extrudate densities decreased as extrusion temperature increased, whereas lower moisture content in the extrudate dough decreased extrudate densities. The elastic modulus and fracture strengths were highly correlated in a power‐law fashion to relative density, showing that the mechanical properties of extrudates were dependent on solid density and foam structure. Up to 48% of the initial lysozyme activity was recovered from the extruded pea starch matrix. The lysozyme released from extrudates showed an inhibition zone against Brochotrix thermosphacta B2. Extruded pea starch matrix containing lysozyme has potential application as an edible and biodegradable packaging material with antimicrobial activity.
Browning Prevention by Ascorbic Acid and 4‐Hexylresorcinol: Different Mechanisms of Action on Polyphenol Oxidase in the Presence and in the Absence of Substrates
Authors: Arias E. , González J. , Peiró J. M. , Oria R. , Lopez‐Buesa P.
Published: October 2007

ABSTRACT: We have investigated the mechanism of action of 4‐hexylresorcinol (4‐HR) and ascorbic acid (AA) on the polyphenol oxidase (PPO) catalyzed oxidation of phenolic substrates. Incubation of PPO with 4‐HR diminishes strongly PPO activity. This effect can be erroneously interpreted, due to the high affinity of 4‐HR for PPO, as irreversible inactivation of PPO. However, PPO activity can be recovered by dialysis after incubation with 4‐HR. 4‐hexylresorcinol is a canonical enzyme inhibitor that binds preferentially to theoxyform of PPO. It is a mixed‐type inhibitor, because it influences both apparentVmax(1.26 compared with 0.4 units in the absence and presence of 4‐HR, respectively) andKmvalues (0.28 mM compared with 0.97 mM in the absence and in the presence of 4‐HR, respectively) of PPO. AA can prevent browning by 2 different mechanisms: In the absence of PPO substrates it inactivates PPO irreversibly, probably through binding to its active site, preferentially in itsoxyform. In the presence of PPO substrates, AA reduces PPO oxidized reaction products, which results in a lag phase when measuring PPO activity by monitoring dark product formation but not when monitoring O2consumption. The simultaneous use of both 4‐HR and AA on PPO results in additive prevention of browning.
Amino Acid, Fatty Acid, and Mineral Profiles of Materials Recovered from Rainbow Trout (Oncorhynchus mykiss) Processing By‐Products Using Isoelectric Solubilization/Precipitation
Authors: Chen Y.‐C. , Tou J.C. , Jaczynski J.
Published: October 2007

ABSTRACT:  Protein, lipid, and insolubles (bones, skin, scales, fins, insoluble protein, and more) were recovered from rainbow trout processing by‐products by means of isoelectric solubilization/precipitation at basic pH and acidic pH. Isoelectric solubilization/precipitation of the trout processing by‐products resulted in the recovery of protein that was higher (P < 0.05) in essential amino acids (EAAs), non‐EAAs, and total EAA/total AA ratio when compared to the processing by‐products. Basic pH treatments yielded a higher (P < 0.05) content of EAAs than the acidic pH treatments. Nutritional quality of the recovered protein was high based on EAAs meeting the FAO/WHO/UNU recommendations for adults. The presence of omega‐3 and omega‐6 fatty acids (ω‐3, ω‐6 FAs) and the ω‐3/ω‐6 ratio in the recovered lipids were similar to the trout processing by‐products, indicating that the pH treatments had no effect on these FAs. Ca and P contents of the processing by‐products exceeded the recommended dietary allowances (RDA), but Fe and Mg did not. Basic pH treatments yielded protein with the lowest (P < 0.05) amount of minerals and the highest (P < 0.05) amount of Ca, P, and Mg in the insolubles when compared to acidic pH. The isoelectric solubilization/precipitation of the processing by‐products effectively removed minerals from the recovered protein without removal of the bones, skin, scales, fins, and so on, prior to processing. The results indicated that isoelectric solubilization/precipitation, particularly at basic pH, permitted recovery of high‐quality protein and lipids from fish processing by‐products for human food uses; also, the recovered insolubles may be used in animal feeds as a source of minerals.
Massive transfusion in trauma patients
Authors: Huber‐Wagner S. , Kanz K. G.
Published: October 2007

About 5–15% of severely injured patients require massive blood transfusion (MBT) defined by the need of equal or more than 10 units of packed red blood cells (PRBCs) within the first post‐traumatic 24 h. Continued haemorrhage is still a leading cause of death in trauma patients. Treatment principles of haemorrhage subsume the surgical control of bleeding and fluid resuscitation. The latter includes not only crystalloid and colloid infusion but also blood component therapy comprising PRBC, fresh frozen plasma, platelets and fibrinogen. In addition, prevention and therapy of hypothermia and acidosis is also an important treatment target. However, there is a lack of definite and evaluated transfusion protocols. According to expert opinion, the relation of PRBC to fresh frozen plasma is recommended to count 1 : 1. One of the topmost complications of haemorrhage in trauma patients comprises the underestimation of coagulopathy and delayed therapy. Being a well‐known fact, coagulopathy significantly increases the probability of mortality. The early recognition of coagulopathy is definitely improved by the use of bedside thrombelastography and thereby provides a basis for its treatment optimization. In general, prognosis of trauma patients receiving MBT has been quite serious in the past. Nevertheless, there is a notable increase of MBT receiving trauma patients’ outcome since the early 1990s. Although MBT is considered as to be an independent mortality risk factor, at least every second trauma patient with MBT survives. No cut‐off value for the number of PRBC could yet be determined in the literature. Thereby, rationale and extended transfusion management even comprising high amounts of blood components is justified.
Preparation and viral inactivation of cryoprecipitate in blood banks in resource‐limited countries
Authors: Burnouf T. , Goubran H. A. , Radosevich M. , El‐Ekiaby M.
Published: October 2007

Non‐virally inactivated cryoprecipitate prepared by blood banks is still used in many countries, especially in the developing world, for the treatment of bleeding disorders due to factor VIII (FVIII), von Willebrand factor (VWF), or fibrinogen deficiency. As a consequence, patients receiving cryoprecipitate are at high risk of being infected by plasma‐borne viruses, such as HIV, and hepatitis B virus (HBV) or C virus (HCV). It is therefore urgent to develop easy‐to‐use, affordable and efficient methods for the viral inactivation of cryoprecipitate under conditions that ensure good maintenance of its haemostatic properties. Preparation of cryoprecipitate from large‐pool solvent‐detergent (SD) plasma seems not economically or technically feasible in developing countries. Cryoprecipitate prepared from single‐donor plasma virally inactivated by methylene‐blue/illumination has significantly reduced content of factor VIII and fibrinogen. There are no data on the quality of cryoprecipitate produced from plasma virally inactivated by techniques in development such as S‐51 psoralen/UV irradiation or by riboflavin/UV irradiation, but loss of FVIII and fibrinogen is reported in S‐51/UV‐treated plasma. Dry‐heat treatments of smallpool cryoprecipitate or intermediate‐purity factor VIII have been developed for use by blood banks, but they are not much used and some have not stopped the risk of transmission of HCV. Recently, a mini‐pool process and a closed bag system to perform SD treatment of cryoprecipitate have been developed for use by blood banks. Recovery of factor VIII, VWF, and fibrinogen is over 95%. Viral validation studies revealed reduction factors of > 4·17, > 4·73, and > 4·72 for HIV, BVDV, and PRV, respectively, within a few minutes of treatment. The SD bag system is in the process of CE‐marking and field testing should start in the near future.
Thalassaemia management in Hong Kong
Authors: Au W.‐Y. , Liang R.
Published: October 2007

Thalassaemia is the most common genetic disease in the world and is especially prevalent in the Asian region. The management of thalassaemia is the combination of public health and clinical efforts. Advances in prenatal diagnosis have made it theoretically possible to reduce new cases of severe thalassaemia to negligible levels. However, this can only be achieved with good maternity public health network and good public education. Thalassaemia major patients rely on chronic transfusion for survival. A safe and affordable blood supply is the prerequisite for any modern thalassaemia management. The most common cause of death in thalassaemia in developed countries is heart failure relating to haemosiderosis. The availability of new oral chelators that can effectively remove cardiac iron and the advent of magnetic resonance imaging monitoring to assess cardiac iron will hopefully give significant impact on thalassaemia survival.
Accuracy of serum transferrin receptor levels in the diagnosis of iron deficiency among hospital patients in a population with a high prevalence of thalassaemia trait
Authors: ONG K. H. , TAN H. L. , TAM L. P. , HAWKINS R. C. W. , KUPERAN P.
Published: October 2007

The diagnosis of iron deficiency in hospital patients can be difficult in the presence of inflammation. A raised serum transferrin receptor (sTfR) level is useful as a marker of iron deficiency as it is unaffected by inflammation. However, diseases that cause an increase in erythropoietic activity can also result in a raised sTfR level. In South‐East Asia, the prevalence of thalassaemia trait is high. As thalassaemia trait is associated with ineffective erythropoiesis and therefore an increase in the sTfR level, we studied the influence of thalassaemia trait on the diagnosis of iron deficiency in hospital patients. Among 431 patients with different combinations of iron deficiency, α‐ and β‐thalassaemia trait, we found that the sTfR level is an excellent diagnostic test for iron deficiency only in patients without thalassaemia trait. α‐Thalassaemia trait worsened its diagnostic accuracy and β‐thalassaemia trait rendered it a non‐diagnostic test. We conclude that in populations with a high prevalence of thalassaemia trait, the sTfR level is not useful in diagnosing iron deficiency unless the patient’s thalassaemia status is known.
Can one single test protocol for provoking exercise‐induced bronchoconstriction also be used for assessing aerobic capacity?*
Authors: Stensrud T. , Carlsen K.‐H.
Published: October 2007

Introduction:  Several different exercise protocols are used to assess exercise‐induced bronchoconstriction (EIB), and to measure peak oxygen uptake (V̇O2 peak) and peak minute ventilation (V̇Epeak).

Objective:  The aim of this study was to evaluate if one single test protocol for assessing EIB can also be used to determine aerobic capacity measured by V̇O2 peak and V̇Epeak.

Methods:  In a randomised cross‐over design, 40 healthy subjects (♀/♂ = 17/23) aged 14–40 years performed two exercise tests on a treadmill. Twenty subjects (♀/♂ = 7/13) performed the two exercise tests at a treadmill inclination of 10.5%; the remaining 20 subjects (♀/♂ = 10/10) performed at an inclination of 5.3%. A common stepwise protocol with 20 min of warming up was compared to an EIB test protocol of an 8‐min treadmill run without warming up, with a workload corresponding to 95% of maximum heart rate during the last 4 min.

Results:  V̇O2 peak did not differ significantly between the two test protocols at 10.5% inclination: 63.3 mL/kg min−1(59.3, 67.4) [mean (95% confidence intervals)] and 63.9 mL/kg min−1 (60.0, 68.0), respectively, or at 5.3% inclination: 56.0 mL/kg min−1 (52.1, 60.0) and 56.1 mL/kg min−1 (51.9, 60.2), respectively. Also, V̇Epeak did not differ between the protocols 158 (144, 173) vs 161 L/min (145, 176) at 10.5% inclination and 123 (114, 132) vs 127 L/min (116, 138) at 5.3% inclination, with the EIB protocol and the stepwise protocol, respectively.

Conclusion:  V̇O2 peak and V̇Epeak did not differ between the two test protocols, and one single standardised EIB test may thus be used both for both provoking EIB and assessing V̇O2 peak.

Please cite this paper as: Stensrud T and Carlsen K‐H. Can one single test protocol for provoking exercise‐induced bronchoconstriction also be used for assessing aerobic capacity? The Clinical Respiratory Journal 2008; 2: 47–53.
Oxidative stress and cerebrovascular dysfunction in mouse models of Alzheimer's disease
Authors: Hamel E. , Nicolakakis N. , Aboulkassim T. , Ongali B. , Tong X‐K.
Published: October 2007

Several factors have been implicated in Alzheimer's disease (AD) but there is no definite conclusion as to the main pathogenic agents. Mutations in the amyloid precursor protein (APP) that lead to increased production of amyloid β peptide (Aβ) are associated with the early‐onset, familial forms of AD. However, in addition to ageing, the most common risk factors for the sporadic, prevalent form of AD are hypertension, hypercholesterolaemia, ischaemic stroke, the ApoE4 allele and diabetes, all characterized by a vascular pathology. In AD, the vascular pathology includes accumulation of Aβ in the vessel wall, vascular fibrosis, and other ultrastructural changes in constituent endothelial and smooth muscle cells. Moreover, the ensuing chronic cerebral hypoperfusion has been proposed as a determinant factor in the accompanying cognitive deficits. In transgenic mice that overexpress mutated forms of the human APP (APP mice), the increased production of Aβ results in vascular oxidative stress and loss of vasodilatory function. The culprit molecule, superoxide, triggers the synthesis of other reactive oxygen species and the sequestration of nitric oxide (NO), thus impairing resting cerebrovascular tone and NO‐dependent dilatations. The Aβ‐induced cerebrovascular dysfunction can be completely abrogated in aged APP mice with antioxidant therapy. In contrast, in mice that overproduce an active form of the cytokine transforming growth factor‐β1 and recapitulate the vascular structural changes seen in AD, antioxidants have no beneficial effect on the accompanying cerebrovascular deficits. This review discusses the beneficial role and limitations of antioxidant therapy in AD cerebrovascular pathology.
Sensory and autonomic nerve changes in the monosodium glutamate‐treated rat: a model of type II diabetes
Authors: Morrison John F. B. , Shehab Safa , Sheen Rajan , Dhanasekaran Subramanian , Shaffiullah Mohammed , Mensah‐Brown Eric
Published: October 2007

Rats that had been injected with monosodium glutamate (MSG) neonatally were studied for up to 70 weeks and compared with age‐matched control rats to study changes in glucose tolerance and in sympathetic and sensory nerves. At 61 and 65 weeks of age, there were significant differences in glucose tolerance between the MSG and control groups, and the MSG group had raised fasting blood glucose. These changes were not associated with changes in the number of β‐cells in the islets of Langerhans. In addition, the diabetic MSG‐treated rats had central obesity and cataracts. Hypoalgesia to thermal stimuli was present in MSG‐treated rats as early as 6 weeks and persisted at 70 weeks. However, no differences were observed in the distribution of substance P, the neurokinin‐1 receptor or calcitonin gene‐related peptide in the dorsal horn of L3–L5 at this age (70 weeks). Diabetic MSG‐treated animals at 65 and 70 weeks of age had significantly reduced noradrenaline concentrations in the heart, tail artery and ileum, while concentrations in the adrenal gland and corpus cavernosum were significantly increased. There was also a significant increase in adrenal adrenaline, dopamine and serotonin, largely attributable to changes in weight of the adrenal gland in the MSG‐treated animals. The results indicate that MSG‐treated animals develop a form of type II diabetes by about 60 weeks of age, and that there are significant changes in amine levels in various tissues associated with these developments.
Resistance training in men is associated with increased arterial stiffness and blood pressure but does not adversely affect endothelial function as measured by arterial reactivity to the cold pressor test
Authors: Kawano Hiroshi , Tanimoto Michiya , Yamamoto Kenta , Sanada Kiyoshi , Gando Yuko , Tabata Izumi , Higuchi Mitsuru , Miyachi Motohiko
Published: October 2007

Resistance training is a popular mode of exercise, but may result in stiffening of the central arteries. Changes in carotid artery diameter were determined using the cold pressor test (CPT), which results in production of nitric oxide via sympathetic activation and is one of the novel methods available for assessing endothelial function in the carotid artery. To investigate the effect of resistance training on endothelial function, we designed a cross‐sectional study of carotid arterial vasoreactivity to CPT in men participating in regular resistance training with increased carotid arterial stiffness compared with age‐matched control subjects. Twelve resistance‐trained middle‐aged men (age 38.7 ± 1.7 years) and 17 age‐matched control subjects (age 36.8 ± 1.2 years) were studied. The direction and magnitude of changes in carotid artery diameter were measured by B‐mode ultrasonography during sympathetic stress induced by submersion of the foot in ice slush for 90 s. Carotid arterial β‐stiffness index, and systolic and mean arterial blood pressure were higher (7.7 ± 0.7 versus 6.0 ± 0.4 arbitrary units, 116 ± 2 versus 131 ± 4 mmHg and 86 ± 2 versus 95 ± 2 mmHg, respectively, all P < 0.05) in the resistance training group compared with control subjects. There were, however, no significant differences in the amount or percentage change in carotid artery diameter in CPT between the two groups (resistance training group, 0.33 ± 0.07 mm and 5.2 ± 1.1%; control group, 0.37 ± 0.06 mm and 5.8 ± 0.9%, respectively). These findings suggest that while carotid arterial stiffening and higher blood pressure are observed in regular resistance‐trained men, these are not associated with abnormalities in carotid arterial vasoreactivity to sympathetic stimulus, which implies intact endothelial function.
The Lomakin Effect in Annular Gas Seals Under Choked Flow Conditions
Authors: Arghir Mihai , Defaye Cyril , Frêne Jean
Published: October 2007

The paper deals with the static stability of annular gas seals under choked flow conditions. For a centered straight annular seal, choking can occur only in the exit section because the gas is constantly accelerated by friction forces. From the mathematical standpoint, the flow choking corresponds to a singularity that was never dealt with numerically. The present work introduces an original numerical treatment of this singularity that is validated by comparisons to the analytical solution for planar channel flow. An interesting observation stemming from these results is that the usual hypothesis of considering the flow as being isothermal is not correct anymore for a gas accelerated by a pressure gradient; the characteristics of the flow are the same but the quantitative results are different. The analysis of eccentric annular seals then shows that choked flow conditions produce a change in the static stiffness. For a subsonic exit section, the Lomakin effect is represented by a centering radial force opposed to the rotor displacement. For a choked exit section, the radial force stemming from an eccentricity perturbation has the same direction as the rotor displacement. The annular seal becomes then statically unstable. From the physical standpoint, this behavior is explained by the modification of the Lomakin effect, which changes sign. The pressure and Mach number variations along the seal depict the influence of high compressible flow regimes on the Lomakin effect. This characteristic has never been depicted before.
Nonlinear Flame Transfer Function Characteristics in a Swirl-Stabilized Combustor
Authors: Bellows Benjamin D. , Bobba Mohan K. , Seitzman Jerry M. , Lieuwen Tim
Published: October 2007

An understanding of the amplitude dependence of the flame response to acoustic excitation is required in order to predict and/or correlate combustion instability amplitudes. This paper describes an experimental investigation of the nonlinear response of a lean, premixed flame to imposed acoustic oscillations. Detailed measurements of the amplitude dependence of the flame response were obtained at approximately 100 test points, corresponding to different flow rates and forcing frequencies. It is observed that the nonlinear flame response can exhibit a variety of behaviors, both in the shape of the response curve and the forcing amplitude at which nonlinearity is first observed. The phase between the flow oscillation and heat release is also seen to have substantial amplitude dependence. The nonlinear flame dynamics appear to be governed by different mechanisms in different frequency and flowrate regimes. These mechanisms were investigated using phase-locked, two- dimensional OH Planar laser-induced fluorescence imaging. From these images, two mechanisms, vortex rollup and unsteady flame liftoff, are identified as important in the saturation of the flame’s response to large velocity oscillations. Both mechanisms appear to reduce the flame’s area and thus its response at these high levels of driving.
A Study on Fluidized Bed-Type Particulate Filter for Diesel Engines
Authors: Kee Sung-Sub , Mohammadi Ali , Ishiyama Takuji , Kakuta Takaaki
Published: October 2007

A fluidized bed-type diesel particulate filter (DPF) was applied to filter particulate matter (PM) in diesel engine exhaust gas. The effects of the fluidized bed design parameters, such as gas velocity, bed particle size, and height, on PM and smoke filtration efficiencies, and pressure drop were experimentally investigated using a single-cylinder direct injection (DI) diesel engine. High PM filtration efficiency and low pressure drop were achieved with the DPF, especially at a lower gas velocity. The PM filtration efficiency was higher with a smaller bed particle size at the lower gas velocity; however, it drastically decreased with an increase in gas velocity due to excessive fluidization of the bed particles. Increase in bed height led to higher PM filtration efficiency while causing an increase in pressure drop. The theoretical work was also conducted for further investigation of the effects of the above-mentioned parameters on PM filtration. These results indicated that diffusion filtration was the dominant mechanism for PM filtration under the conditions of this study and that the decrease in PM filtration efficiency at high gas velocity was caused by a deterioration in the diffusion filtration. The bed particle diameter and the bed height should be optimized in order to obtain a high filtration efficiency without increasing the DPF size.
The Maximum Power Operating Point for a Combustion-Driven Thermoelectric Converter With Heat Recirculation
Authors: Peterson Richard B.
Published: October 2007

A model is developed for determining the ideal operating point, based on maximum power output, for a thermoelectric conversion (TEC) element coupled to a combustor. In the analysis, heat recirculation from the combustor exhaust is included. Results presented here are relevant to the operating characteristics of small, combustion-driven energy systems. The model is composed of a TEC element, a combustor, a counterflow heat exchanger, and a thermal shunt resistance to the surroundings. Including the shunt is necessary due to the increased importance of this effect in small-scale thermal systems. From this combination of components, an optimal combustor operating temperature is found giving maximum power output and efficiency. The model is used to determine ideal performance figures as a function of system parameters such as the effectiveness of heat regeneration, loss of heat by conduction, and the parameters describing the thermoelectric conversion element (the so-called ZT parameter). Although a high degree of idealization is employed, the results show the importance of heat recirculation and the significance of thermal losses on system operation.
A New Bump-Type Foil Bearing Structure Analytical Model
Authors: Le Lez Sébastien , Arghir Mihaï , Frene Jean
Published: October 2007

A gas bearing of bump foil type comprises an underlying structure made of one or several strips of corrugated sheet metal covered by a top foil surface. The fluid film pressure needs to be coupled with the behavior of the structure for obtaining the whole bearing characteristics. Unlike in classical elasto-aerodynamic models, a foil bearing (FB) structure has a very particular behavior due to friction interfaces, bump interactions, and nonisotropic stiffness. Some authors have studied this complex behavior with the help of three-dimensional finite element simulations. These simulations evidenced a lack of reliable analytical models that can be easily implemented in a FB prediction code. The models found in the literature tend to overestimate the foil flexibility because most of them do not consider the interactions between bumps that are highly important. The present work then develops a model that describes the FB structure as a multidegree of freedom system of interacting bumps. Each bump includes three degrees of freedom linked with elementary springs. The stiffnesses of these springs are analytically expressed so that the model can be adjusted for any dimensions and material properties. Once the stiffness matrix of the whole FB structure is obtained, the entire static system is solved taking friction into account. Despite its relative simplicity, comparisons with finite elements simulations for various static load distributions and friction coefficients show a good correlation. This analytical model has been integrated into a foil bearing prediction code. The load capacity of a first generation foil bearing was then calculated using this structure model as well as other simplified theoretical approaches. Significant differences were observed, revealing the paramount influence of the structure on the static and dynamic characteristics of the foil bearing. Some experimental investigations of the static stiffness of the structure were also realized for complete foil bearings. The structure reaction force was calculated for a shaft displacement with zero rotation speed, using either the multidegree of freedom model or the usual stiffness formulas. The comparisons between theoretical and experimental results also tend to confirm the importance of taking into account the bump interactions in determining the response of the structure.
Removal of bone in CT angiography by multiscale matched mask bone elimination
Authors: Gratama van Andel H. A. F. , Venema H. W. , Streekstra G. J. , van Straten M. , Majoie C. B. L. M. , den Heeten G. J. , Grimbergen C. A.
Published: October 2007

For clear visualization of vessels in CT angiography (CTA) images of the head and neck using maximum intensity projection (MIP) or volume rendering (VR) bone has to be removed. In the past we presented a fully automatic method to mask the bone [matched mask bone elimination (MMBE)] for this purpose. A drawback is that vessels adjacent to bone may be partly masked as well. We propose a modification, multiscale MMBE, which reduces this problem by using images at two scales: a higher resolution than usual for image processing and a lower resolution to which the processed images are transformed for use in the diagnostic process. A higher in‐plane resolution is obtained by the use of a sharper reconstruction kernel. The out‐of‐plane resolution is improved by deconvolution or by scanning with narrower collimation. The quality of the mask that is used to remove bone is improved by using images at both scales. After masking, the desired resolution for the normal clinical use of the images is obtained by blurring with Gaussian kernels of appropriate widths. Both methods (multiscale and original) were compared in a phantom study and with clinical CTA data sets. With the multiscale approach the width of the strip of soft tissue adjacent to the bone that is masked can be reduced from 1.0 to 0.2 mm without reducing the quality of the bone removal. The clinical examples show that vessels adjacent to bone are less affected and therefore better visible. Images processed with multiscale MMBE have a slightly higher noise level or slightly reduced resolution compared with images processed by the original method and the reconstruction and processing time is also somewhat increased. Nevertheless, multiscale MMBE offers a way to remove bone automatically from CT angiography images without affecting the integrity of the blood vessels. The overall image quality of MIP or VR images is substantially improved relative to images processed with the original MMBE method.
A simple geometric algorithm to predict optimal starting gantry angles using equiangular‐spaced beams for intensity modulated radiation therapy of prostate cancer
Authors: Potrebko Peter S. , McCurdy Boyd M. C. , Butler James B. , El‐Gubtan Adel S. , Nugent Zoann
Published: October 2007

A fast, geometric beam angle optimization (BAO) algorithm for clinical intensity‐modulated radiation therapy (IMRT) was implemented on ten localized prostate cancer patients on the Radiation Therapy Oncology Group (RTOG) 0126 protocol. The BAO algorithm computed the beam intersection volume (BIV) within the rectum and bladder using five and seven equiangular‐spaced beams as a function of starting gantry angle for comparison to the V and V . A mathematical theory was presented to explain the correlation of BIV with dose and dose‐volume metrics. The class solution ‘W’ pattern in the rectal V and V as a function of starting gantry angle using five equiangular‐spaced beams (with two separate minima centered near 20° and 50°) was reproduced by the 5 BIV within the rectum. A strong correlation was found between the rectal 5 BIV and the rectal V and V as a function of starting gantry angle. The BAO algorithm predicted the location of the two dosimetric minima in rectal V and V (optimal starting gantry angles) to within 5°. It was demonstrated that the BIV geometric variations for seven equiangular‐spaced beams were too small to translate into a strong dosimetric effect in the rectal V and V . The relatively flat distribution with starting gantry angle of the bladder V and V was reproduced by the bladder five and seven BIV for each patient. A geometric BAO method based on BIV has the advantage over dosimetric BAO methods of simplicity and rapid computation time. This algorithm can be used as a standalone optimization method or act as a rapid calculation filter to reduce the search space for a dosimetric BAO method. Given the clinically infeasible computation times of many dosimetric beam orientation optimization algorithms, this robust geometric BIV algorithm has the potential to facilitate beam angle selection for prostate IMRT in clinical practice.
Optimal kVp selection for dual‐energy imaging of the chest: Evaluation by task‐specific observer preference tests
Authors: Williams D. B. , Siewerdsen J. H. , Tward D. J. , Paul N. S. , Dhanantwari A. C. , Shkumat N. A. , Richard S. , Yorkston J. , Van Metter R.
Published: October 2007

Human observer performance tests were conducted to identify optimal imaging techniques in dual‐energy (DE) imaging of the chest with respect to a variety of visualization tasks for soft and bony tissue. Specifically, the effect of kVp selection in low‐ and high‐energy projection pairs was investigated. DE images of an anthropomorphic chest phantom formed the basis for observer studies, decomposed from low‐energy and high‐energy projections in the range and , respectively, with total dose for the DE image equivalent to that of a single chest radiograph. Five expert radiologists participated in observer preference tests to evaluate differences in image quality among the DE images. For visualization of soft‐tissue structures in the lung, the pair provided optimal image quality, whereas proved optimal for delineation of the descending aorta in the retrocardiac region. Such soft‐tissue detectability tasks exhibited a strong dependence on the low‐kVp selection (with providing maximum soft‐tissue conspicuity) and a weaker dependence on the high‐kVp selection (typically highest at ). Qualitative examination of DE bone‐only images suggests optimal bony visualization at a similar technique, viz., . Observer preference was largely consistent with quantitative analysis of contrast, noise, and contrast‐to‐noise ratio, with subtle differences likely related to the imaging task and spatial‐frequency characteristics of the noise. Observer preference tests offered practical, semiquantitative identification of optimal, task‐specific imaging techniques and will provide useful guidance toward clinical implementation of high‐performance DE imaging systems.
A global calibration model for EPIDs used for transit dosimetry
Authors: Nijsten S. M. J. J. G. , van Elmpt W. J. C. , Jacobs M. , Mijnheer B. J. , Dekker A. L. A. J. , Lambin P. , Minken A. W. H.
Published: October 2007

Electronic portal imaging devices (EPIDs) are not only applied for patient setup verification and detection of organ motion but are also increasingly used for dosimetric verification. The aim of our work is to obtain accurate dose distributions from a commercially available amorphous silicon EPID for transit dosimetry applications. For that purpose, a global calibration model was developed, which includes a correction procedure for ghosting effects, field size dependence and energy dependence of the EPID response. In addition, the long‐term stability and additional buildup material for this type of EPID were determined. Differences in EPID response due to photon energy spectrum changes have been measured for different absorber thicknesses and field sizes, yielding off‐axis spectrum correction factors based on transmission measurements. Dose measurements performed with an ionization chamber in a water tank were used as reference data, and the accuracy of the dosimetric calibration model was determined for a large range of treatment conditions. Gamma values using 3% as dose‐difference criterion and as distance‐to‐agreement criterion were used for evaluation. The field size dependence of the response could be corrected by a single kernel, fulfilling the gamma evaluation criteria in case of virtual wedges and intensity modulated radiation therapy fields. Differences in energy spectrum response amounted up to 30%–40%, but could be reduced to less than 3% using our correction model. For different treatment fields and (in)homogeneous phantoms, transit dose distributions satisfied in almost all situations the gamma criteria. We have shown that EPIDs can be accurately calibrated for transit dosimetry purposes
Design and implementation of a water phantom for IMRT, arc therapy, and tomotherapy dose distribution measurements
Authors: Pallotta Stefania , Marrazzo Livia , Bucciolini Marta
Published: October 2007

The aim of this paper is to present a new phantom for arc therapy, intensity‐modulated radiation therapy (IMRT), and tomotherapy dose distribution measurement in pretreatment verification. The presented phantom is innovative for its use of water as the tissue equivalent material, together with a technical solution specifically designed to support radiographic or radiochromic film and ionization chambers in any desired position. The phantom comprise a container, whose present shape and dimensions offer the possibility to simulate a human torso or abdomen; the container can be filled with water by opening the upper cover. On the internal side of the cover, a set of carbon pipes can support film in the desired coronal, axial, or sagittal planes. At one of the two ends of the phantom, an ionization chamber can be positioned parallel to the rotation axis of the accelerator gantry in all possible positions within a diameter cylinder, for film calibration purposes. Inhomogeneities can be inserted into the phantom using the same carbon pipes and plastic sheets used to support film. An example of vertebra‐shaped inserts made of bone equivalent material is reported. Radiochromic film can be dipped in water, while radiographic film must be protected to prevent damage. To accomplish this, radiographic film is laminated using a cold laminating film. In order to assess the effects of both the lamination itself and the effects of water on laminated Kodak EDR2 film, the optical density (OD) of conventional, laminated, and laminated film immersed in water and exposed to a range of doses from 0 to 300 cGy were compared. The OD of the three samples receiving the same radiation dose did not present any significant difference, thus proving that laminated EDR2 film can also be used in water. A prerequisite for any dosimetric comparison between planned and measured data is a proper film to plan registration. The solution proposed here is an extrinsic in‐plane registration technique using four reference points marked on each film in predefined positions. The four points and the millimeter scales fixed on the carbon pipes that support the film are designed and manufactured so as to transfer onto the film the same reference system used during the planning procedure, thus allowing a straightforward registration. Tests to assess the accuracy of the proposed registration method demonstrate that the distances between measured and intended marker positions, evaluated for coronal, axial, and sagittal planes, were about for both anteroposterior and lateral projections.
Diagnosis of Parkinsonian disorders using a channelized Hotelling observer model: Proof of principle
Authors: Bal H. , Bal G. , Acton P. D.
Published: October 2007

Imaging dopamine transporters using PET and SPECT probes is a powerful technique for the early diagnosis of Parkinsonian disorders. In order to perform automated accurate diagnosis of these diseases, a channelized Hotelling observer (CHO) based model was developed and evaluated using the SPECT tracer [Tc‐99m]TRODAT‐1. Computer simulations were performed using a digitized striatal phantom to characterize early stages of the disease (20 lesion‐present cases with varying lesion size and contrast). Projection data, modeling the effects of attenuation and geometric response function, were obtained for each case. Statistical noise levels corresponding to those observed clinically were added to the projection data to obtain 100 noise realizations for each case. All the projection data were reconstructed, and a subset of the transaxial slices containing the striatum was summed and used for further analysis. CHO models, using the Laguerre–Gaussian functions as channels, were designed for two cases: (1) By training the model using individual lesion‐present samples and (2) by training the model using pooled lesion‐present samples. A decision threshold obtained for each CHO model was used to classify the study population . It was observed that individual lesion trained CHO models gave high diagnostic accuracy for lesions that were larger than those used to train the model and vice‐versa. On the other hand, the pooled CHO model was found to give a high diagnostic accuracy for all the lesion cases (average diagnostic ; Fisher's exact test). Based on our results, we conclude that a CHO model has the potential to provide early and accurate diagnosis of Parkinsonian disorders, thereby improving patient management.