bluuebunny/crossref_metadata_2025 huggingface dataset:
Coercivity and microstructure of Mn–Ni–N sintered alloys
Authors: Sugimoto S. , Isogai K. , Hattori T. , Matsumoto H. , Yoshida S. , Tezuka N.
Published: December 2007

This paper describes the relationship between magnetic properties and microstructure in Mn‐Ni‐N sintered alloys. The Mn‐Ni‐N alloy heat‐treated at 1200 °C for 3 h and then jacket‐quenched in a nitrogen atmosphere, exhibits a high coercivity of 352 kAm‐1. The EDX analysis reveals that the sample jacket‐quenched and then annnealed in nitrogen, consists of two phases with different Ni content forming a lamellar structure. From TEM observations, the jacket‐quenched sample contains many stacking faults and twins with nano‐meter size. Therefore, it is considered that they play a role as pinning sites of domain wall motion and high coercivity observed with the quenched sample is casued by the domain wall pinning mechanism. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Recent developments toward understanding magnetization processes in Nd‐Fe‐B permanent magnet materials
Authors: Hirosawa S. , Fukagawa T. , Maki T.
Published: December 2007

The quick rise of an enormous market of high‐coercivity grades of Nd‐Fe‐B sintered magnets for hybrid electric vehicles (HEV) has created a new concern about resources of certain elements such as Tb and Dy which is used in order to guarantee stability of magnetic flux at operating temperatures. Accordingly, improvements of coercivity in the Nd‐Fe‐B magnets at elevated temperatures without heavily using these scarece elements are required. For this goal, deeper understanding of the coercivity mechanism is neccesarry. In order to clearly study the relationship beween local microstructure and coercivity related to that microstructure, an approach using a model magnet composed of a thin sintered magnet and an Nd layer doposited on its surface is reported. Besides this micropscopic apporach, macroscopic approaches are also indespensable. Also described in this paper is investigation of successive recoil curves and their relation with magnetic domain structures in a system composed of submicron size grains of Nd2Fe14B that can be prepared by means of hydrogenation‐disproportionation‐dehydrogenation‐decomposition process. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of interface intermixing on the magnetoresistive and the exchange coupling in bottom‐ and top‐spin valves
Authors: Kim Jong Soo , Park Dae‐Won , Lee Seong‐Rae
Published: December 2007

We investigated the interfacial mixing phenomena associated with magnetoresistance and exchange coupling in a top spin valve (T‐SV) and bottom spin valve (B‐SV) at IrMn/CoFe and CoFe/IrMn interfaces. The difference in the surface free energies of IrMn and CoFe is the major factor determining the degree to which interfacial mixing occurs, but it depends on the deposition sequence. A B‐SV featuring a gradational IrMn/CoFe interface had a small Hex in the as‐deposited state, but showed improved exchange coupling on annealing as a result of limited interdiffusion. By contrast, a T‐SV featuring a sharp CoFe/IrMn interface had a high Hex in the as‐deposited state, but suffered a reduction in exchange coupling on annealing, due to a moderate level of interdiffusion. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Annealing temperature dependence of microwave permeability in CoFe/MnIr bilayers
Authors: Kim Dong Young , Parvatheeswara Rao B. , Kim Chong‐Oh , Tsunoda Masakiyo , Takahashi Migaku
Published: December 2007

We measured microwave permeability in thermal annealed CoFe/MnIr bilayers. The ferromagnetic resonance frequency (fFMR) and Gilbert damping constant (αG) are analyzed using the Landau‐Lifshitz‐Gilbert equation. The fFMR increases with the exchange bias field, and it can be easily tuned over 10 GHz either by controlling the CoFe thickness or through modifications of unidirectional anisotropy by thermal annealing. The extracted αG is inversely proportional to the exchange bias field, and this behavior is caused by the suppression of the anisotropy field distribution due to an increase in the exchange bias field. Thus, low loss performance in microwave frequency range can be achieved in exchange biased CoFe/MnIr bilayers. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Exchange bias effect in Fe films deposited on Si(100) substrates
Authors: Wang Wenhong , Takano Fumiyoshi , Takenaka Masato , Ofuchi Hironori , Akinaga Hiro
Published: December 2007

The crystal structure and exchange bias effect in Fe films deposited on Si(100) substrates have been investigated. X‐ray diffraction and fluorescence‐extended X‐ray absorption fine structure measurements reveal that the as‐deoposited Fe films are polycrystalline with a preferred (110) texture. In addition, we observe a shift in the magnetic hysteresis loop of Fe films deposited on Si (100) where there is existance of a thin oxidized layer. By comparison, for Fe film deposited on Si(100) lacking the oxidized layer, it does not exhibit any features of shift in the magnetic hysteresis loop. We postulate the effect results from a coupling between the ferromagnetic Fe film and the antiferromagnetic Fe oxide that forms spontaneously in the interface. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Design and construction of a claw‐pole PM dynamo
Authors: Hwang C. C. , Li P. L. , Lai Y. C. , Liang C. H.
Published: December 2007

This paper aims to develop a claw‐pole permanent magnet (PM) dynamo for the generation of electric power for bicycles. The design of the machine is done with the aid of electromagnetic field analysis based on the finite element method (FEM). The prototype dynamo has been simulated and tested under no‐load and load conditions. The comparison of terminal voltages between the predicted and measured is seen to be excellent. The generation of terminal voltage of the dynamo meets the voltage requirement for bicycles. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A superconductor material model for hysteresis losses computation
Authors: Satiramatekul Thitipong , Bouillault Frédéric
Published: December 2007

The aim of this work was to calculate the hysteresis losses in the superconductor materials. For that, we used one macroscopic model which obtained by altering Bean's model. We propose the finite element method for the numerical modeling. Our problem consists of an infinitely long superconducting line plunged in a uniform field varying periodically in time. In this paper, we present the influence of the shape and the amplitude of the applied magnetic field to the instantaneous losses. We also present two various methods for calculating the average losses. Moreover, we could in particular obtain the quantities such as the current density or the magnetization in order to know the phenomenon of superconductivity in superconductor materials. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Annealing effect on an exchange‐biasing Co/IrMn system
Authors: Chen Yuan‐Tsung , Jen S. U. , Yao Y. D. , Liao J. H. , Wu T. B.
Published: December 2007

The top‐configuration Co(y)/IrMn(90 Å) exchange‐biasing phenomenon has been studied by sputtering method with two conditions: (a) the substrate temperature (Ts) was kept at room temperature (RT) only, and (b) Ts = RT with an in‐plane field (h) = 500 Oe deposition and postdeposition annealing in the field at TA = 250 °C for 1 h, with the samples field cooled to RT. High resolution electron cross‐sectional transmission electron microscopy (HR X‐TEM) reveals that the IrMn (111) texturing plays a main role to exchange‐biasing field (Hex) and interfacial energy (Jk). The Hex versus y result shows that Hex increases when y decreases in case (b). Since Jk = HexMsy, where Ms is Co magnetization, it is easy to derive Hex = Jk/(Msy). Therefore, if Hex is inversely proportional to y, with Jk/Ms constant, we find Hexy = constant. In case (a), Hex is very small in general, while in case (b), Hex is of the order of 60‐180 Oe. Moreover, the y dependence of Jk is similar to that of Ms for each curve. Finally, the Hc is inversely proportional to y because of the surface pinning effects from the Ta/Co and Co/IrMn interfaces. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bayesian monitoring to detect a shift in process mean
Authors: Marcellus Richard L.
Published: December 2007

A Bayesian analogue of the Shewhart X‐bar chart is defined and compared with cumulative sum charts. The comparison identifies types of production process where the Bayesian chart has better expected performance than the cumulative sum chart. Implementing the Bayesian chart requires more detailed knowledge of the process structure than is required by the best‐known types of charts, but acquiring this information can yield tangible benefits. Copyright © 2007 John Wiley & Sons, Ltd.
Comparison of linear predictors obtained by data transformation, generalized linear models (GLM) and response modeling methodology (RMM)
Authors: Shore Haim
Published: December 2007

The data‐transformation approach and generalized linear modeling both require specification of a transformation prior to deriving the linear predictor (LP). By contrast, response modeling methodology (RMM) requires no such specifications. Furthermore, RMM effectively decouples modeling of the LP from modeling its relationship to the response. It may therefore be of interest to compare LPs obtained by the three approaches. Based on numerical quality problems that have appeared in the literature, these approaches are compared in terms of both the derived structure of the LPs and goodness‐of‐fit statistics. The relative advantages of RMM are discussed. Copyright © 2007 John Wiley & Sons, Ltd.
A comparison of two methods of analysing staircase fatigue test data
Authors: Grove Daniel , Campean Felician
Published: December 2007

When the fatigue strength of components or material is tested by the staircase or up‐and‐down method, the data can be analysed in either the fatigue strength domain, which is the most popular approach, or the life domain, based on life regression models. In this paper we exploit a simple relationship between families of models in the two domains to obtain an estimate of the distribution of fatigue strength directly from a fitted life regression model. We use simulation to compare the two approaches, concluding that for estimating important features of the fatigue strength distribution the method of maximum likelihood is more effective if it is applied in the life domain. In particular, it is more robust to the choice of xh, the step height of the staircase, provided xh is in the range σX–2σX, where σX is the standard deviation of the log‐strengths. Most of our results are insensitive to the value of the initial stress amplitude. Copyright © 2007 John Wiley & Sons, Ltd.
Prediction of the Watson Characterization Factor of Hydrocarbon Components from Molecular Properties
Authors: Gharagheizi Farhad , Fazeli Ali
Published: December 2007

In the present work, a Quantitative Structure–Property Relationship (QSPR) study was performed to predict the Watson characterization factor of hydrocarbon components. A Genetic Algorithm‐based Multivariate Linear Regression (GA‐MLR) was applied to select the most statistically effective molecular descriptors of the Watson characterization factor. Then, based on the selected molecular descriptors by GA‐MLR, a three‐layer Feed Forward Neural Network (FFNN) was constructed to predict the Watson characterization factor. The obtained results showed that the constructed FFNN can accurately predict the Watson characterization factor of hydrocarbon components.
Prediction of Flash Point Temperature of Pure Components Using a Quantitative Structure–Property Relationship Model
Authors: Gharagheizi Farhad , Alamdari Reza Fareghi
Published: December 2007

In this work, a general Quantitative Structure–Property Relationship (QSPR) model ($\rm{ R^2 = 0.9669}$, $\rm{ Q_{{\rm{LOO}}}^{\rm{2}} = 0.9663}$, and $\rm{ s = 12.691}$) for the prediction of flash points of 1030 pure compounds is developed. Genetic Algorithm‐based Multivariate Linear Regression (GA‐MLR) technique is used to select four chemical structure‐based molecular descriptors from a pool containing 1664 molecular descriptors.
Maintaining network connectivity and performance in robot teams
Authors: Hsieh M. Ani , Cowley Anthony , Kumar Vijay , Taylor Camillo J.
Published: December 2007

In this paper, we present an experimental study of strategies for maintaining end‐to‐end communication links for tasks such as surveillance, reconnaissance, and target search and identification, where team connectivity is required for situational awareness. Our main contributions are threefold: (a) We present the construction of a radio signal strength map that can be used to plan multi‐robot tasks, and also serve as useful perceptual information. We show how a nominal model of an urban environment obtained by aerial surveillance, is used to generate strategies for exploration. (b) We present reactive controllers for communication link maintenance; and (c) we consider the differences between monitoring signal strength versus data throughput. Experimental results, obtained using our multi‐robot testbed in three representative urban environments are presented with each of our main contributions. © 2008 Wiley Periodicals, Inc.
Supporting wilderness search and rescue using a camera‐equipped mini UAV
Authors: Goodrich Michael A. , Morse Bryan S. , Gerhardt Damon , Cooper Joseph L. , Quigley Morgan , Adams Julie A. , Humphrey Curtis
Published: December 2007

Wilderness Search and Rescue (WiSAR) entails searching over large regions in often rugged remote areas. Because of the large regions and potentially limited mobility of ground searchers, WiSAR is an ideal application for using small (human‐packable) unmanned aerial vehicles (UAVs) to provide aerial imagery of the search region. This paper presents a brief analysis of the WiSAR problem with emphasis on practical aspects of visual‐based aerial search. As part of this analysis, we present and analyze a generalized contour search algorithm, and relate this search to existing coverage searches. Extending beyond laboratory analysis, lessons from field trials with search and rescue personnel indicated the immediate need to improve two aspects of UAV‐enabled search: How video information is presented to searchers and how UAV technology is integrated into existing WiSAR teams. In response to the first need, three computer vision algorithms for improving video display presentation are compared; results indicate that constructing temporally localized image mosaics is more useful than stabilizing video imagery. In response to the second need, a goal‐directed task analysis of the WiSAR domain was conducted and combined with field observations to identify operational paradigms and field tactics for coordinating the UAV operator, the payload operator, the mission manager, and ground searchers. © 2008 Wiley Periodicals, Inc.
Hough based terrain classification for realtime detection of drivable ground
Authors: Poppinga Jann , Birk Andreas , Pathak Kaustubh
Published: December 2007

The usability of mobile robots for surveillance and search and rescue missions can be significantly improved by adding intelligent functionalities that decrease the cognitive load on the operator or that even allow autonomous behavior of the robots, e.g., when communication fails. Mobility in this regard is not only the mechatronic endeavor of developing suited locomotion apparatuses, but also a perception, modeling, and planning challenge. Here, the perception issue of detecting drivable ground is addressed, a particularly important issue for safety, security, and rescue robots, which have to operate in a vast range of unstructured, challenging environments. The simple yet efficient approach is based on the Hough transform of planes. The idea is to design the parameter space such that drivable surfaces can be easily detected by the number of hits in the bins corresponding to drivability. A decision tree on the bin properties increases robustness as it allows the robot to handle uncertainties, especially sensor noise. In addition to the binary distinction of drivable/nondrivable ground, a classification of terrain types is possible. The algorithm is applied to 3D data obtained from two different sensors, namely, a near‐infrared time of flight camera and a stereo camera. Experimental results are presented for typical indoor as well as outdoor terrains, demonstrating robust realtime detection of drivable ground. Seven datasets recorded indoors and outdoors under very varying conditions are used for this purpose. About 6800 snapshots of range data are processed in total. It is shown that drivability can be robustly detected with success rates ranging between 83% and 100%. Computation is extremely fast in the order of 5 to 50 ms. © 2008 Wiley Periodicals, Inc.
Change in teachers' knowledge of subject matter: A 17‐year longitudinal study
Authors: Arzi Hanna J. , White Richard T.
Published: December 2007

This longitudinal study explored change in teachers' knowledge of subjects they teach from preservice training through 17 years of professional experience. It followed secondary school science teachers in Australia, through sequences of individual interviews in which change in content knowledge (mainly energy‐related) was probed primarily via concept profiles—a word‐association method. Change was found to be multifaceted, with details of unused content fading from memory, alongside growth that results from improved understanding and reorganization of structure more than from accretion of new material. Across personal and professional life tracks that produce variation between individuals, development is facilitated by “critical mass” of teachers' knowledge and interest in their chosen disciplines of study and certification, whereas deficiencies tend to persist in the other subjects they are asked to teach. The required curriculum is the single most powerful determinant of teacher knowledge, serving as both its organizer and source. Based on the study, a three‐phase model of teacher content‐knowledge development is proposed, and the discussion highlights the need for career‐long support for growth, even in teachers' major subjects where expertise is taken for granted. © 2007 Wiley Periodicals, Inc. Sci Ed 92:221–251, 2008
Examining the cognitive processes used by adolescent girls and women scientists in identifying science role models: A feminist approach
Authors: Buck Gayle A. , Clark Vicki L. Plano , Leslie‐Pelecky Diandra , Lu Yun , Cerda‐Lizarraga Particia
Published: December 2007

Women remain underrepresented in science professions. Studies have shown that students are more likely to select careers when they can identify a role model in that career path. Further research has shown that the success of this strategy is enhanced by the use of gender‐matched role models. While prior work provides insights into the value of using role models, it does not explain the cognitive process involved in girls identifying role models from nontraditional careers for women. This feminist study addresses this gap by examining the cognitive process eighth‐grade girls use in identifying a person as a science role model and comparing it to the process used by women scientists seeking to serve as possible science role models. Data revealed that the girls' process in identifying a role model involved personal connections and their initial image of a scientist led them to believe they could not have such a connection with a scientist. The initial views expressed by the women suggested they felt pressure to portray “perfect“ scientists in order to be a role model. A common understanding of a science role model was realized only after changes occurred in the girls' image of scientists and the scientists' image of a role model. The catalysts for these changes were the relationships that developed between girls and women scientists. © 2007 Wiley Periodicals, Inc. Sci Ed 92:688–707, 2008
Using data mining to predict K–12 students' performance on large‐scale assessment items related to energy
Authors: Liu Xiufeng , Ruiz Miguel E.
Published: December 2007

This article reports a study on using data mining to predict K–12 students' competence levels on test items related to energy. Data sources are the 1995 Third International Mathematics and Science Study (TIMSS), 1999 TIMSS‐Repeat, 2003 Trend in International Mathematics and Science Study (TIMSS), and the National Assessment of Educational Progress (NAEP). Student population performances, that is, percentages correct, are the object of prediction. Two data mining algorithms, C4.5 and M5, are used to construct a decision tree and a linear function to predict students' performance levels. A combination of factors related to content, context, and cognitive demand of items and to students' grade levels are found to predict student population performances on test items. Cognitive demands have the most significant contribution to the prediction. The decision tree and linear function agree with each other on predictions. We end the article by discussing implications of findings for future science content standard development and energy concept teaching. © 2007 Wiley Periodicals, Inc. J Res Sci Teach 45: 554–573, 2008
Parastomal Hernia‐Repair Using Mesh and an Open Technique
Authors: Guzmán‐Valdivia Gilberto , Guerrero Teresa Soto , Laurrabaquio Hilda Varela
Published: December 2007

Introduction

Parastomal hernia occurs in 35%‐50% of patients who have had a stoma formed, whether for the digestive tract or the urinary tract. There are many repair techniques including primary repair and repair using different types of mesh prosthesis, and the surgical approach may be open or laparoscopic. However, all techniques suffer the disadvantage of a high index of hernia recurrence.

Patients and methods

This study included 125 patients from the stoma clinic at our hospital. Hernia repair was performed on 25 of these patients who had a terminal colostomy because of either cancer or inflammatory disease. Preoperative colon preparation involved a cathartic, an evacuating enema, and antibiotic therapy in the preoperative period. The repair was conducted via an anterior approach, dissecting the skin around the stoma in the way a plastic surgeon handles an umbilical scar during abdominoplasty, in order to enter the hernia site. The hernial sac was left intact to form a bed on which to lay a lightweight polypropylene mesh, and this was then fixed to the deep face of the aponeurosis all around the stoma, with sutures placed in a U‐shape with 1/0 or 2/0 non‐absorbent material. The mesh was also fixed to the external surface of the colon with simple sutures of 3/0 polyglycocolic acid. A closed supra‐aponeurotic drain was left in situ, and the skin was closed with 3/0 nylon.

Results

Of the corpus, 50 patients presented with parastomal hernia (40%), and 25 of them underwent surgery. These patients were followed for a period of 12 months, on average (range: 8–24 months). After operation, 2 patients (8%) experienced hernia recurrence and underwent further surgery to reinforce the abdominal wall with a new insertion of mesh prosthesis; 2 patients (8%) suffered surgical wound infection; and 2 patients (8%) developed a seroma. There was no rejection of the mesh, erosion of the colon, or fistula formation.

Conclusions

Inserting a mesh prosthesis by this technique is a safe effective treatment for parastomal hernia, adding another option to the available repair solutions. Prospective and comparative studies are required to reinforce this study, and they should ideally include a greater number of patients in the study corpus.
Current Status of the Surgical Treatment of Atrial Fibrillation
Authors: Geha Alexander S. , Abdelhady Khaled
Published: December 2007

Atrial fibrillation (AF) affects several million patients worldwide and is associated with a number of heart conditions, particularly coronary artery disease, rheumatic heart disease, hypertension, and congestive heart failure. The treatment of AF and its complications is quite costly. Atrial fibrillation usually results from multiple macro‐re‐entrant circuits in the left atrium. Very frequently, particularly in association with mitral valve disease, these circuits arise from the area of the junction of the pulmonary venous endothelium and the left atrial endocardium. Pharmacological therapy is at best 50% effective. Therapeutic options for AF include antiarrhythmic drugs, cardioversion, atrioventricular (A‐V) node block, pacemaker insertion, and ablative surgery. In 1987, Cox developed an effective surgical procedure to achieve ablation. Current ablative procedures include the classic cut‐and‐sew Maze operation or a modification of it, namely through catheter ablation, namely, cryoablation, radiofrequency ablation (dry or irrigated), and other forms of ablation (e.g., laser, microwave). These procedures will be described, along with the indications, advantages and disadvantages of each. Special emphasis on the alternative means to cutting and sewing to achieve appropriate effective atrial scars will be stressed, and our experience with these approaches in 50 patients with AF and associated cardiac lesions and their outcomes is presented.
Incidence of 3‐hydroxy‐3‐methylglutaryl‐coenzyme A lyase (HL) deficiency in Brazil, South America
Authors: Vargas C. R. , Sitta A. , Schmitt G. , Ferreira G. C. , Cardoso M. L. , Coelho D. , Gibson K. M. , Wajner M.
Published: December 2007

3‐Hydroxy‐3‐methylglutaryl‐CoA lyase (HL) deficiency (3‐hydroxy‐3‐methylglutaric aciduria, 3‐HMG) is a rare autosomal recessive inborn error of metabolism involving the final step of leucine degradation. HL is the key enzyme for the production of glucose‐sparing ketone bodies for brain. Positive biochemical findings are metabolic acidosis, hyperammonaemia, and hypoketotic hypoglycaemia in the neonatal period or infancy. In the present study we report 15 Brazilian patients with HL deficiency and present their clinical and biochemical findings. Urine from all patients contained large amounts of 3‐hydroxy‐3‐methylglutaric, 3‐methylglutaconic, 3‐hydroxyisovaleric and 3‐methylglutaric acids, and 3‐methylcrotonylglycine was also observed in 13 patients. The main features at clinical presentation were hypoglycaemia (12 patients), seizures (10 patients), metabolic acidosis (9 patients), vomiting (6 patients), and hepatomegaly (5 patients). All but two patients were of Portuguese ancestry. HL deficiency comprised 7.3% of total organic acidurias detected in our laboratory during a 13‐year time span, indicating a high incidence of this disorder in Brazil. Limited molecular characterization (4/15 patients only) revealed two mutations common for individuals of Portuguese/Spanish (Iberian Peninsula) ancestry (E37X and V168fs(−2)). Our findings increase the number of HL‐deficient patients and reinforce the characteristic phenotypic picture of the disease. Effective dietary interventions based on mild protein restriction and avoidance of fasting and possibly alternative C5 ketone body generating therapy for this disorder may provide further impetus and rationale for expanded newborn screening of HL deficiency.
Responses of Caragana korshinskii Kom. to shoot removal: mechanisms underlying regrowth
Authors: Fang Xiangwen , Li Jinhua , Xiong Youcai , Xu Danghui , Fan Xianwei , Li Fengmin
Published: December 2007

Caragana korshinskii Kom. a dominant member of desert flora in north‐western China, is often subjected to aboveground shoot destruction but is very successful in its rapid recovery. We investigated the physiological basis for resprouting by comparing shoot elongation, leaf‐nutrient content, pre‐dawn leaf‐water potential (LWP), root non‐structural carbohydrate (TNC), and photosynthetic rate of first‐year resprouts with those of adjacent undamaged individuals. C. korshinskii resprouts had a significantly higher rate of shoot elongation. Plant responses associated with enhanced shoot elongation included (1) improved water status, (2) drawing upon more TNC from roots to support aboveground shoot regrowth, (3) enhanced photosynthetic rate owing to improved water status and increased nutrient content in leaves, and (4) allocating more photosynthate to vegetative production without reproduction costs. Maintaining an active root system after shoot removal may be the foundation which engenders these mechanisms underlying rapid regrowth of C. korshinskii in the disturbed environment.
Bayesian IRT Guessing Models for Partial Guessing Behaviors
Authors: Cao Jing , Stokes S. Lynne
Published: December 2007

According to the recent Nation’s Report Card, 12th-graders failed to produce gains on the 2005 National Assessment of Educational Progress (NAEP) despite earning better grades on average. One possible explanation is that 12th-graders were not motivated taking the NAEP, which is a low-stakes test. We develop three Bayesian IRT mixture models to describe the results from a group of examinees including both nonguessers and partial guessers. The first assumes that the guesser answers questions based on his or her knowledge up to a certain test item, and guesses thereafter. The second model assumes that the guesser answers relatively easy questions based on his or her knowledge and guesses randomly on the remaining items. The third is constructed to describe more general low-motivation behavior. It assumes that the guesser gives less and less effort as he or she proceeds through the test. The models can provide not only consistent estimates of IRT parameters but also estimates of each examinee’s nonguesser/guesser status and degree of guessing behavior. We show results of a simulation study comparing the performance of the three guessing models to the 2PL-IRT model. Finally, an analysis of real data from a low-stakes test administered to university students is presented.
The Hospital for the Ruptured and Crippled: William Bradley Coley, Third Surgeon-in-Chief 1925–1933
Authors: Levine David B.
Published: December 2007

In January 1925, the Board of Managers of the New York Society for the Relief of the Ruptured and Crippled appointed William Bradley Coley, M.D., age 63, Surgeon-in-Chief of the Hospital for the Ruptured and Crippled (R & C) to succeed Virgil P. Gibney who submitted his resignation the month before. It would be the first time a general surgeon held that position at the oldest orthopedic hospital in the nation, now known as Hospital for Special Surgery (HSS). Coley had been on staff for 36 years and was world famous for introducing use of toxins to treat malignant tumors, particularly sarcomas. A graduate of Yale College and Harvard Medical College, Coley interned at New York Hospital and was appointed, soon after, to the staff of the New York Cancer Hospital (now Memorial Sloan Kettering Cancer Center) located at that time at 106th Street on the West Side of New York. With his mentor Dr. William Bull, Coley perfected the surgical treatment of hernias at R & C. He was instrumental in raising funds for his alma maters, Yale, Harvard and Memorial Hospital. His crusade in immunology as a method of treatment for malignant tumors later fell out of acceptance in the medical establishment. After his death in 1936, an attempt to revive interest in use of immunotherapy for inoperable malignancies was carried out by his daughter, Helen Coley Nauts, who pursued this objective until her death at age 93 in 2000. Coley's health deteriorated in his later years, and in 1933, he resigned as chief of Bone Tumors at Memorial Hospital and Surgeon-in-Chief at R & C, being succeeded at Ruptured and Crippled as Surgeon-in-Chief by Dr. Eugene H. Pool. William Bradley Coley died of intestinal infarction in 1936 and was buried in Sharon, Connecticut.
Boron Fullerenes: A First-Principles Study
Authors: Gonzalez Szwacki Nevill
Published: December 2007

A family of unusually stable boron cages was identified and examined using first-principles local-density functional method. The structure of the fullerenes is similar to that of the B12icosahedron and consists of six crossing double-rings. The energetically most stable fullerene is made up of 180 boron atoms. A connection between the fullerene family and its precursors, boron sheets, is made. We show that the most stable boron sheets are not necessarily precursors of very stable boron cages. Our finding is a step forward in the understanding of the structure of the recently produced boron nanotubes.
High‐Throughput Analysis of Plasma Fatty Acid Methyl Esters Employing Robotic Transesterification and Fast Gas Chromatography
Authors: Masood M. Athar , Salem Norman
Published: December 2007

Fatty acid analysis is an important research tool, and indices derived from essential fatty acid contents serve as useful biomarkers related to cardiovascular and other chronic disease risk. Both clinical and basic studies of essential fatty acid composition are becoming ever larger in magnitude leading to delays while the rather laborious lipid analyses are performed. A robotic transesterification procedure has been developed for high‐throughput analysis of plasma fatty acid methyl esters. In this approach, robots perform most steps including plasma and reagent transfer, transesterification reaction via heating at 80 °C in open tubes with multiple reagent additions, followed by two‐phase extraction and transfer of lipid extracts to GC vials. The vials are then placed directly onto a GC autosampler carousel for robotic sample injection. An improved fast GC method is presented in which the peaks of interest are eluted within 6 min. This method is readily scalable to prepare and analyze 200 samples per day (1,000 samples per week) so that large clinical trials can be accommodated.
Altered Lipid Response in Hamsters Fed cis‐9,trans‐11+trans‐8,cis‐10 Conjugated Linoleic Acid Mixture
Authors: Bissonauth Vishnee , Chouinard P. Yvan , Marin Johanne , Leblanc Nadine , Richard Denis , Jacques Hélène
Published: December 2007

The objective of the present study was to compare the effects of cis‐9,trans‐11 + trans‐8,cis‐10 conjugated linoleic acid (CLA) mixture to those of cis‐9,trans‐11 + trans‐10,cis‐12 CLA mixture and linoleic acid (LA) on lipoprotein profile, hepatic lipids, body composition and digestibility of dietary fat in hamsters (n = 17) fed diets containing 2% of experimental fat (w/w) for 28 days. The cis‐9,trans‐11 + trans‐10,cis‐12 CLA mixture showed higher LDL cholesterol concentrations than LA and the cis‐9,trans‐11 + trans‐8,cis‐10 CLA mixture. The cis‐9,trans‐11 + trans‐8,cis‐10 CLA mixture induced similar plasma LDL cholesterol and hepatic lipid concentrations, and coefficient of digestibility as LA, indicating no effect of the trans‐8,cis‐10 CLA isomer on these lipid parameters. On the other hand, the cis‐9,trans‐11 + trans‐8,cis‐10 CLA mixture induced higher plasma VLDL cholesterol and triglycerides than LA and the cis‐9,trans‐11 + trans‐10,cis‐12 CLA mixture. The cis‐9,trans‐11 + trans‐8,cis‐10 CLA mixture also induced the highest plasma glucose concentrations compared with the two other groups, indicating an impairment of glycemic control. No differences in body composition were noted between the three groups. The present results thus show that the cis‐9,trans‐11 + trans‐8,cis‐10 CLA mixture can deteriorate plasma VLDL cholesterol and triglycerides in hamsters, possibly due to an increased flux of glucose.
Validation of a Rapid Measure of Blood PUFA Levels in Humans
Authors: Bailey‐Hall Eileen , Nelson Edward B. , Ryan Alan S.
Published: December 2007

An assay involving a finger stick and filter paper blood spotting was developed to determine polyunsaturated fatty acid (PUFA) levels in blood. Capillary whole blood from a finger stick was blotted on antioxidant impregnated filter paper, air dried, saponified and methylated using sodium hydroxide and boron trifluoride in methanol. The method differed from those described previously because separation of plasma and red blood cells (RBCs) was not needed, thin‐layer chromatography (TLC) was not required to separate phospholipids, initial extraction of lipids before transesterification was not necessary, and the fatty acid methyl ester (FAME) method was able to methylate steryl esters, free fatty acids, and sphingomyelins. Twenty‐six subjects provided blood samples by finger stick and venipuncture. Levels of long‐chain polyunsaturated fatty acids (LC‐PUFA) from capillary whole blood were correlated with those from RBCs and PLs in venous blood (P < 0.001, R2 ranged from 0.64 to 0.86). Although highly significant (P < 0.002), the R2 values for the correlation between arachidonic acid (ARA) levels in capillary whole blood with ARA levels in RBCs and plasma phospholipids (PLs) were relatively lower (R2 = 0.31–0.41, respectively). Results indicate that the described finger stick assay represents a fast, reliable method to measure specific LC‐PUFA levels.
Direct Microwave Transesterification of Fingertip Prick Blood Samples for Fatty Acid Determinations
Authors: Armstrong Jeff M. , Metherel Adam H. , Stark Ken D.
Published: December 2007

Omega‐3 polyunsaturated fatty acid (PUFA) dietary intakes and tissue levels are positively associated with various health benefits. The development of cost efficient, high throughput methodologies would enable research in large clinical and population studies, and clinical fatty acid profiling. Microwave heating for the transesterification of blood fatty acids was examined. Samples were collected by venous puncture and fingertip prick onto chromatography paper. Aliquots of serum, plasma, erythrocytes and whole blood were prepared from venous blood. Boron trifluoride in methanol was used for transesterification but sample preparation and heating varied. Fatty acid determinations and markers of omega‐3 fatty acid status including the sum of eicosapentaenoic acid and docosahexaenoic acid, the ratio of total n‐3 PUFA to n‐6 PUFA, and the percentage of n‐3 highly unsaturated fatty acids (HUFA, ≥20 carbons and ≥3 carbon–carbon double bonds) in total HUFA were compared. Quantitative determinations indicate that microwave transesterification results in significantly lower estimates of monounsaturates and polyunsaturates, possibly through incomplete transesterification of triacylglycerols. However, qualitative estimates of omega‐3 fatty acid status were relatively similar. Fingertip prick blood collection combined with direct transesterification by microwave may be a very rapid method to estimate omega‐3 fatty acid status for selected applications.
Evaluation of Methyl Esters of Mahua Oil (Madhuca Indica) as Diesel Fuel
Authors: Kapilan N. , Reddy R. P.
Published: December 2007

There is increasing interest in India for suitable alternative fuels that are environment friendly. This search has led to mahua oil (MO) as one alternative for diesel fuel in India. Mahua oil methyl esters (MOME) were prepared by transesterification using potassium hydroxide (KOH) as catalyst and nuclear magnetic resonance (NMR) testing was done to determine the conversion of vegetable oil to biodiesel (MOME). The properties of MOME were close to those of diesel oil. Engine testing was conducted using a single‐cylinder 4‐stroke direct‐injection, constant‐speed compression‐ignition diesel engine using MO, MOME and B20 as fuels. The engine ran smoothly with MOME and B20, but heavy smoke emissions were observed when MO was used as fuel.
Recovery of Natural Antioxidants from Olive Mill Wastewater Using Genapol‐X080
Authors: Gortzi Olga , Lalas Stavros , Chatzilazarou Arhontoula , Katsoyannos Evangelos , Papaconstandinou Spyros , Dourtoglou Euthalia
Published: December 2007

The possibility of applying cloud point extraction (CPE) using Genapol X‐080 as surfactant for the separation of phenolic compounds from olive mill wastewater was examined. The ability of the surfactant to recover individual and mixtures of polyphenols and tocopherols in various concentrations from aqueous solutions was tested before its application for the recovery of phenols from olive mill wastewater. Many of the examined individual polyphenols were recovered at high percentage. Especially, in the case of Luteolin, low surfactant concentrations were sufficient for quantitative removal. The recovery appeared proportional to the surfactant concentration. The complete recovery of tocopherols was also possible. Total phenol recovery by simple and successive CPE of olive mill wastewater with various concentrations (2, 5 and 20%, v/v) of Genapol X‐080 was up to 89.5%.
Genotype and Growing Environment Effects on the Tocopherols and Fatty Acids of Brassica napus and B. juncea
Authors: Richards Amy , Wijesundera Chakra , Salisbury Phil
Published: December 2007

The effects of genotype and growing environment on the tocopherols and fatty acids (FA) of experimental Brassica juncea and B. napus breeding lines were investigated. For both species, with the exception of a few genotypes, the concentration ratio of γ‐tocopherols to α‐tocopherol was practically constant. The genotype influenced the tocopherol concentration in B. napus, and to a lesser degree, B. juncea. The environment also had a similar effect, and a positive correlation existed between the daily maximum temperature and the α‐tocopherol concentration in B. napus. Genotype effects on the FA composition were significant for the conventional but not for Clearfield or triazine tolerant traits of B. napus. The genotype had no effect on the FA of the B. juncea genotypes. In contrast, the growing environment had a significant influence on the FA composition of both species with apparent influence from temperature and rainfall. For both species, the concentration of γ‐tocopherol as well as total tocopherols was inversely related to the 18:3 concentration, which could have resulted from opposite and independent effects of temperature on the two variables. No relationship existed between the concentrations of tocopherol and the remaining unsaturated FA 18:1 and 18:2. The positional distribution of unsaturated FA within the oil triacylglycerol was a function of their total concentration.
Non-normality and nonlinearity in combustion–acoustic interaction in diffusion flames
Authors: BALASUBRAMANIAN KOUSHIK , SUJITH R. I.
Published: December 2007

The role of non-normality and nonlinearity in flame–acoustic interaction in a ducted diffusion flame is investigated in this paper. The infinite rate chemistry model is employed to study unsteady diffusion flames in a Burke–Schumann type geometry. It has been observed that even in this simplified case, the combustion response to perturbations of velocity is non-normal and nonlinear. This flame model is then coupled with a linear model of the duct acoustic field to study the temporal evolution of acoustic perturbations. The one-dimensional acoustic field is simulated in the time domain using the Galerkin technique, treating the fluctuating heat release from the combustion zone as a compact acoustic source. It is shown that the coupled combustion–acoustic system is non-normal and nonlinear. Further, calculations showed the occurrence of triggering; i.e. the thermoacoustic oscillations decay for some initial conditions whereas they grow for some other initial conditions. It is shown that triggering occurs because of the combined effect of non-normality and nonlinearity. For such a non-normal system, resonance or ‘pseudoresonance’ may occur at frequencies far from its natural frequencies. Non-normal systems can be studied using pseudospectra, as eigenvalues alone are not sufficient to predict the behaviour of the system. Further, both necessary and sufficient conditions for the stability of a thermoacoustic system are presented in this paper.
A computational parameter study for the three-dimensional shock–bubble interaction
Authors: NIEDERHAUS JOHN H. J. , GREENOUGH J. A. , OAKLEY J. G. , RANJAN D. , ANDERSON M. H. , BONAZZA R.
Published: December 2007

The morphology and time-dependent integral properties of the multifluid compressible flow resulting from the shock–bubble interaction in a gas environment are investigated using a series of three-dimensional multifluid-Eulerian simulations. The bubble consists of a spherical gas volume of radius 2.54 cm (128 grid points), which is accelerated by a planar shock wave. Fourteen scenarios are considered: four gas pairings, including Atwood numbers −0.8 <A< 0.7, and shock strengths 1.1 <M≤ 5.0. The data are queried at closely spaced time intervals to obtain the time-dependent volumetric compression, mean bubble fluid velocity, circulation and extent of mixing in the shocked-bubble flow. Scaling arguments based on various properties computed from one-dimensional gasdynamics are found to collapse the trends in these quantities successfully for fixedA. However, complex changes in the shock-wave refraction pattern introduce effects that do not scale across differing gas pairings, and for some scenarios withA> 0.2, three-dimensional (non-axisymmetric) effects become particularly significant in the total enstrophy at late times. A new model for the total velocity circulation is proposed, also based on properties derived from one-dimensional gasdynamics, which compares favourably with circulation data obtained from calculations, relative to existing models. The action of nonlinear-acoustic effects and primary and secondary vorticity production is depicted in sequenced visualizations of the density and vorticity fields, which indicate the significance of both secondary vorticity generation and turbulent effects, particularly forM> 2 andA> 0.2. Movies are available with the online version of the paper.
Particle-phase distributions of pressure-driven flows of bidisperse suspensions
Authors: NORMAN JAY T. , OGUNTADE BABATUNDE O. , BONNECAZE ROGER T.
Published: December 2007

The phase distribution of a bimodal distribution of negatively buoyant particles in a low-Reynolds-number pressure-driven flow of a suspension in a horizontal pipe is measured using multi-frequency electrical impedance tomography (EIT). Suspensions of heavy silver-coated particles and slightly heavy PMMA particles exhibit different effective conductivities depending on the frequency of an applied electrical current. This difference allows the separate imaging of the phase distribution of each particle type and the composite suspension. At low flow rates the dense particles tend to distribute in the lower half of the pipe The particles are resuspended toward the centre as the flow rate is increased. The slightly heavy particles tend to accumulate closer to the centre of the pipe. The presence of the nearly neutrally buoyant particles enhances the resuspension of the heavy particles compared to that of a suspension of heavy particles alone at the same volume fraction. A suspension balance model is used to theoretically predict the distribution of particles in the flow assuming an ideal mixing rule for the particle partial pressures. The agreement between the predictions and the experimental observations is qualitatively correct and quantitatively fair.
Steady periodic waves in a three-layer fluid with shear in the middle layer
Authors: CHEN MICHAEL J. , FORBES LAWRENCE K.
Published: December 2007

A three-layer intrusion flow is considered, in which all three layers are in motion, with different speeds, relative to the observer. Shear is present in the middle layer, and the lowest fluid may even move oppositely to the upper two (so giving an exchange flow). Two thin interfaces are present, above and below the moving middle layer. A linearized analysis is presented for small wave amplitudes. Nonlinear periodic solutions are then obtained using a Fourier technique, and reveal a range of nonlinear phenomena, including limiting waves, multiple solutions and resonances.