bluuebunny/crossref_metadata_2025 huggingface dataset:
A hierarchical Bayesian model for a variability analysis of measurements of occupational n-hexane exposure in Italy
Authors: Toti Simona , Biggeri Annibale , Baldasseroni Alberto
Published: June 2006

This study evaluates changes over time in occupational exposure to n-hexane by longitudinal repeated measurements analysis of data from the Biological Monitoring Registry from 1991 to 1998. The main sources of variability in n-hexane exposure among manufacturing workers in Florence province (Italy) are inspected. The 2,5-hexanedione concentrations in urine of industrial workers are explained by structural, individual and factory information. Here we analyse the effectiveness of a 1994 law on workplace conditions based on variability decomposition of measured 2,5-hexanedione concentrations.

We propose a hierarchical Bayesian model which takes into account the different levels of aggregation of data. The results show that for leather and shoe factories, the within-subject and within-factory variance components remain the most important over the time of study, whereas the between-factory components decreased in accordance with the expected effect of the new legislation.
Binomial thinning models for integer time series
Authors: Jung Robert C , Tremayne A R
Published: June 2006

This article considers some simple observation-driven time series models for counts. We provide a brief description of the class of integer-valued autoregressive (INAR) and integer-valued moving average (INMA) processes. These classes of models may be attractive when the data exhibit a significant serial dependence structure. We, therefore, briefly review various testing procedures useful for assessing the serial correlation in the data. Once it is established that the data are not serially independent, suitable INAR or INMA processes may be employed to model the data. In the important first order INAR model, we discuss various methods of estimating the structural parameters of the process. We also give a short account of the extension of some of these estimation procedures to second order INAR models. Moving average counterparts of both models are also entertained. Throughout, the models and methods are illustrated in the context of a famous data set from the branching process literature that turns out to be surprisingly difficult to model satisfactorily.
Comparing vocational training courses through a discrete-time multilevel hazard model
Authors: Paccagnella O
Published: June 2006

In this article, the author provides an econometric approach for comparing vocational training courses, and aims to study how courses affect individual behaviour. Given the hierarchical nature of the data and the purposes of the analysis, he proposes the application of a discrete-time multilevel hazard model. The variable of interest is the duration (in months) of the first job-search after the end of the course. The author focusses on contextual and correlated (course) effects and comments on the results also in terms of school effectiveness. The approach may be easily applied to several other clustered structures.
Prognostic Value of Nodal Ratios in Node-Positive Breast Cancer
Authors: Woodward Wendy A. , Vinh-Hung Vincent , Ueno Naoto T. , Cheng Yee Chung , Royce Melanie , Tai Patricia , Vlastos Georges , Wallace Anne Marie , Hortobagyi Gabriel N. , Nieto Yago
Published: June 2006

Purpose

The American Joint Committee on Cancer staging system for breast cancer was recently updated to reflect the impact of increasing the absolute number of positive lymph nodes on prognosis. However, numerous studies suggest that nodal ratios (absolute number of involved nodes–number of nodes resected) may have greater prognostic value than absolute numbers of involved nodes. Here we examine the data supporting the use of nodal ratios in breast cancer prognosis and consider the potential advantages and disadvantages of including nodal ratios in breast cancer staging.

Methods

A systematic review of the literature was conducted using the following search engines: http://www.google.com ; Thomson's ISI Web of Science; PubMed.

Results

In multiple reports from both prospective and retrospectively collected data sets, nodal ratios have been shown to be significant predictors of outcome, including locoregional recurrence and overall survival. These studies span all stages of breast cancer and include various treatments as well as various statistical approaches.

Conclusion

There is considerable data supporting the use of nodal ratios in breast cancer prognosis. A thorough and methodological evaluation of the potential prognostic importance of nodal ratios in large multicenter data sets is merited and is currently being undertaken by the International Nodal Ratio Working Group.
Ghrelin Stimulates Gastric Emptying and Hunger in Normal-Weight Humans
Authors: Levin F. , Edholm T. , Schmidt P. T. , Grybäck P. , Jacobsson H. , Degerblad M. , Höybye C. , Holst J. J. , Rehfeld J. F. , Hellström P. M. , Näslund E.
Published: June 2006

Context: Ghrelin is produced primarily by enteroendocrine cells in the gastric mucosa and increases gastric emptying in patients with gastroparesis.

Main Objective: The objective of the study was to evaluate the effect of ghrelin on gastric emptying, appetite, and postprandial hormone secretion in normal volunteers.

Design: This was a randomized, double-blind, crossover study.

Subjects: Subjects included normal human volunteers and patients with GH deficiency.

Intervention: Intervention included saline or ghrelin (10 pmol/kg·min) infusion for 180 min after intake of a radioactively labeled omelette (310 kcal) or GH substitution in GH-deficient patients.

Main Outcome Measures: Measures consisted of gastric empty-ing parameters and postprandial plasma levels of ghrelin, cholecystokinin, glucagon-like peptide-1, peptide YY, and motilin.

Results: The emptying rate was significantly faster for ghrelin (1.26 ± 0.1% per minute), compared with saline (0.83% per minute) (P < 0.001). The lag phase (16.2 ± 2.2 and 26.5 ± 3.8 min) and half-emptying time (49.4 ± 3.9 and 75.6 ± 4.9 min) of solid gastric emptying were shorter during ghrelin infusion, compared with infusion of saline (P < 0.001). The postprandial peak in plasma concentration for cholecystokinin and glucagon-like peptide-1 occurred earlier and was higher during ghrelin infusion. There was no significant effect of ghrelin on plasma motilin or peptide YY. There was no difference in gastric emptying before and after GH substitution.

Conclusion: Our results demonstrate that ghrelin increases the gastric emptying rate in normal humans. The effect does not seem to be mediated via GH or motilin but may be mediated by the vagal nerve or directly on ghrelin receptors in the stomach. Ghrelin receptor agonists may have a role as prokinetic agents.
Influence of the BRAF V600E Mutation on Expression of Vascular Endothelial Growth Factor in Papillary Thyroid Cancer
Authors: Jo Young Suk , Li Shengjin , Song Jung Hun , Kwon Ki Hyun , Lee Jun Chul , Rha So Young , Lee Hyo Jin , Sul Ji Young , Kweon Gi Ryang , Ro Heung-kyu , Kim Jin-Man , Shong Minho
Published: June 2006

Context: The BRAF mutation may influence the expression patterns of molecular markers that are related to the development and progression of thyroid cancer.

Objective: The objective of the study was to investigate the effects of the BRAF V600E mutation on expression of galectin-3, cyclooxygenase-2, cyclin D1, p53, and vascular endothelial growth factor (VEGF) in papillary thyroid cancer (PTC).

Design, Setting, and Subjects: One hundred sixty-three PTC and 28 nodular hyperplasia patients were selected retrospectively. The presence of the BRAF V600E mutation and the level of expression of the molecular markers were determined.

Results: Of 161 PTC patients, 102 patients (63.4%) were BRAF V600E(+), and these cases had significantly larger tumor sizes (P = 0.01), compared with V600E(−) cases (n = 59, 36.6%). Although PTC tissues had higher expression levels of the selected molecular markers than nodular hyperplasia tissues, expression levels of several molecular markers in BRAF V600E(+) PTC were not significantly different from those of BRAF V600E(−) PTC. But VEGF was significantly up-regulated in BRAF V600E(+) PTC, compared with BRAF V600E(−) PTC. VEGF expression levels were strongly positively correlated to tumor size (P < 0.001), extrathyroidal invasion (P = 0.02), and tumor stage (P = 0.04). Multivariate analysis clearly showed that VEGF expression was up-regulated in BRAF V600E(+) PTC (odds ratio 2.5, confidence interval 1.1–5.6; P = 0.03).

Conclusions: BRAF V600E(+) PTC tended to have larger tumor volumes and higher expression of VEGF. The level of VEGF expression was closely correlated with tumor size, extrathyroidal invasion, and stage. The relatively high levels of VEGF expression may be related to poorer clinical outcomes and recurrences in BRAF V600E(+) PTC.
Whole Genome Expression Profiling of Glucose-Dependent Insulinotropic Peptide (GIP)- and Adrenocorticotropin-Dependent Adrenal Hyperplasias Reveals Novel Targets for the Study of GIP-Dependent Cushing’s Syndrome
Authors: Lampron Antoine , Bourdeau Isabelle , Hamet Pavel , Tremblay Johanne , Lacroix André
Published: June 2006

Context: The mechanisms responsible for the ectopic adrenal expression of glucose-dependent insulinotropic peptide (GIP) receptor (GIPR) in GIP-dependent Cushing’s syndrome (CS) are unknown. Chronic adrenal stimulation by ACTH in Cushing’s disease or GIP in GIP-dependent ACTH-independent macronodular adrenal hyperplasia both lead to the induction of genes implicated in adrenal proliferation and steroidogenesis.

Objective: The objective of the study was to identify genes differentially expressed specifically in GIP-dependent CS that could be implicated in the ectopic expression of GIPR.

Methods: We used the Affymetrix U133 plus 2.0 microarray oligochips to compare the whole genome expression profile of adrenal tissues from five cases of GIP-dependent bilateral ACTH-independent macronodular adrenal hyperplasia with CS, one case of GIP-dependent unilateral adenoma with CS, five cases of ACTH-dependent hyperplasias, and a pool of adrenals from 62 normal individuals.

Results: After data normalization and statistical filtering, 723 genes with differential expression were identified, including 461 genes or sequences with a known functional implication, classified in eight dominant functional classes. Specific findings include repression of perilipin, the overexpression of 13 G protein-coupled receptors, and the potential involvement of Rho-GTPases. We also isolated 94 probe sets potentially linked to the formation of GIP-dependent nodules adjacent to the diffuse hyperplasia. These included probe sets related to the linker histone H1 and repression of RXRa and CCND2. The expression profiles for eight genes were confirmed by real-time RT-PCR.

Conclusion: This study identified an extensive series of potentially novel target candidate genes that could be implicated in the molecular mechanisms of ectopic expression of the GIPR as well as in the multistep progression of GIP-dependent CS.
Exercise Restores Skeletal Muscle Glucose Delivery But Not Insulin-Mediated Glucose Transport and Phosphorylation in Obese Subjects
Authors: Slimani L. , Oikonen V. , Hällsten K. , Savisto N. , Knuuti J. , Nuutila P. , Iozzo P.
Published: June 2006

Context/Objective: Insulin resistance in obese subjects results in the impaired disposal of glucose by skeletal muscle. The current study examined the effects of insulin and/or exercise on glucose transport and phosphorylation in skeletal muscle and the influence of obesity on these processes.

Subjects/Methods: Seven obese and 12 lean men underwent positron emission tomography with 2-deoxy-2-[18F]fluoro-d-glucose in resting and isometrically exercising skeletal muscle during normoglycemic hyperinsulinemia. Data were analyzed by two-tissue compartmental modeling. Perfusion and oxidative capacity were measured during insulin stimulation by [15O]H2O and [15O]O2.

Results: Exercise increased glucose fractional uptake (K), inward transport rate (K1), and the k3 parameter, combining transport and intracellular phosphorylation, in lean and obese subjects. In each group, there was no statistically significant difference between plasma flow and K1. At rest, a significant defect in K1 (P = 0.0016), k3 (P = 0.016), and K (P = 0.022) was found in obese subjects. Exercise restored K1, improved but did not normalize K (P = 0.03 vs. lean), and did not ameliorate the more than 60% relative impairment in k3 in obese individuals (P = 0.002 vs. lean). The glucose oxidative potential tended to be reduced by obesity.

Conclusions/Interpretation: The study indicates that exercise restores the impairment in insulin-mediated skeletal muscle perfusion and glucose delivery associated with obesity but does not normalize the defect involving the proximal steps regulating glucose disposal in obese individuals. Our data support the use of 2-deoxy-2-[18F]fluoro-d-glucose-positron emission tomography in the dissection between substrate supply and intrinsic tissue metabolism.
Activin Modulates the Transcriptional Response of LβT2 Cells to Gonadotropin-Releasing Hormone and Alters Cellular Proliferation
Authors: Zhang Hao , Bailey Janice S. , Coss Djurdjica , Lin Bo , Tsutsumi Rie , Lawson Mark A. , Mellon Pamela L. , Webster Nicholas J. G.
Published: June 2006

Both GnRH and activin are crucial for the correct function of pituitary gonadotrope cells. GnRH regulates LH and FSH synthesis and secretion and gonadotrope proliferation, whereas activin is essential for expression of FSH. Little is known, however, about the interplay of signaling downstream of these two hormones. In this study, we undertook expression profiling to determine how activin pretreatment alters the transcriptional response of LβT2 gonadotrope cells to GnRH stimulation. Activin treatment alone altered the transcriptional profile of 303 genes including inducing that of the 17β-hydroxysteroid dehydrogenase B1 gene that converts estrone to 17β-estradiol, altering the sensitivity of the cells to estrone. Furthermore, activin had a dramatic effect on the response of LβT2 cells to GnRH. Hierarchical clustering of 2453 GnRH-responsive genes identified groups of genes the response of which to GnRH was either enhanced or blunted after activin treatment. Mapping of these genes to gene ontology classifications or signaling pathways highlighted significant differences in the classes of altered genes. In the presence of activin, GnRH regulates genes in pathways controlling cell energetics, cytoskeletal rearrangements, organelle organization, and mitosis in the absence of activin, but genes controlling protein processing, cell differentiation, and secretion. Therefore, we demonstrated that activin enhanced GnRH induction of p38MAPK activity, caused GnRH-dependent phosphorylation of p53, and reduced the ability of GnRH to cause G1 arrest. Thus, although activin alone changes a modest number of transcripts, activin pretreatment dramatically alters the response to GnRH from an antiproliferative response to a more differentiated, synthetic response appropriate for a secretory cell.
The fission yeast Chs2 protein interacts with the type-II myosin Myo3p and is required for the integrity of the actomyosin ring
Authors: Martín-García Rebeca , Valdivieso M.-Henar
Published: June 2006

In Schizosaccharomyces pombe cytokinesis requires the function of a contractile actomyosin ring. Fission yeast Chs2p is a transmembrane protein structurally similar to chitin synthases that lacks such enzymatic activity. Chs2p localisation and assembly into a ring that contracts during division requires the general system for polarised secretion, some components of the actomyosin ring, and an active septation initiation network. Chs2p interacts physically with the type-II myosin Myo3p revealing a physical link between the plasma membrane and the ring. In chs2Δ mutants, actomyosin ring integrity is compromised during the last stages of contraction and it remains longer in the midzone. In synchronous cultures, chs2Δ cells exhibit a delay in septation with respect to the control strain. All these results show that Chs2p participates in the correct functioning of the medial ring.
Postanaesthetic tracheal strictures in three rabbits
Authors: Grint N J , Sayers I R , Cecchi R , Harley R , Day M J
Published: June 2006

Within an 11-day period, three rabbits were anaesthetized for neutering. All were endotracheally intubated with 12 cm long, 2.5 mm (inner diameter [ID]) polyvinylchloride (PVC) tubes. All rabbits developed clinical signs of dyspnoea and upper respiratory tract obstruction, 17–21 days later. One rabbit was found dead; the other two were treated, but one was euthanized and one died. At necropsy examination, focal chronic inflammation and significant localized narrowing of the tracheal lumen was found in all cases. The affected sites corresponded to the position of the bevel of the endotracheal tube (ETT) during anaesthesia. Histopathology could not differentiate between a traumatic or chemical cause for the narrowing. Possible causes include trauma by the bevel of the ETT when turning the rabbit or preparing the surgical site or a chemical burn from incorrect disinfection or inadequate rinsing of the tubes. Iatrogenic tracheitis should be considered as a cause of dyspnoea, when clinical signs arise 2–3 weeks after anaesthesia.
Low frequency of Helicobacter species in the stomachs of experimental rabbits
Authors: Van den Bulck K , Decostere A , Baele M , Marechal M , Ducatelle R , Haesebrouck F
Published: June 2006

The natural occurrence of established Helicobacter species was investigated in the stomachs of 65 laboratory rabbits, by means of polymerase chain reaction (PCR) (65/65) and histological analysis (51/65). The degree of inflammation in the different regions of the rabbits' stomach was evaluated on haematoxylin and eosin (HE)-stained histological slides. Four rabbits were found positive for Helicobacter species by PCR. Based on 16S ribosomal ribonucleic acid (rRNA) sequences, H. canadensis/H. pullorum organisms were identified in three animals. Bacteria were seen on merely one histological slide from one of these animals. H. felis was identified in one rabbit. Histological examination revealed no inflammation in the stomachs of 40 rabbits, while moderate gastric inflammation was seen in 11 animals, mainly in the antrum. In conclusion, the stomach of the laboratory rabbits included in the study was occasionally found positive for Helicobacter species, which were mostly identified as enterohepatic helicobacters, probably reflecting a mere passage of these bacteria through the stomach.
The impact of different blood sampling methods on laboratory rats under different types of anaesthesia
Authors: Fitzner Toft Martin , Petersen Mikkel Haxø , Dragsted Nils , Hansen Axel Kornerup
Published: June 2006

Rats with implanted telemetry transponders were blood sampled by jugular puncture, periorbital puncture or tail vein puncture, or sampled by jugular puncture in carbon dioxide (CO2), isoflurane or without anaesthesia in a crossover design. Heart rate, blood pressure and body temperature were registered for three days after sampling. Initially blood pressure increased, but shortly after sampling it decreased, which led to increased heart rate. Sampling induced rapid fluctuations in body temperature, and an increase in body temperature. Generally, rats recovered from sampling within 2–3 h, except for rats sampled from the tail vein, which showed fluctuations in body temperature in excess of 30 h after sampling. Increases in heart rate and blood pressure within the first hours after sampling indicated that periorbital puncture was the method that had the largest acute impact on the rats and that it might take an extra hour to recover from it. CO2 anaesthesia seemed unable to prevent the increase in blood pressure and the fluctuations in body temperature induced by blood sampling, and up to 10 h after sampling, the rats were still affected by CO2 anaesthesia. Rats anaesthetized with isoflurane showed lower increases in blood pressure after, and fewer fluctuations in body temperature during sampling, and the post-anaesthetic effects of isoflurane, if any, seemed to disappear immediately after sampling. It is, therefore, concluded that blood sampling in rats by jugular puncture seems to be the method from which rats most rapidly recover when compared with periorbital puncture and tail vein puncture, and that for anaesthesia, isoflurane is recommended in preference to CO2.
Non-surgical alternatives to invasive procedures in mice
Authors: Marini J C , Lee B , Garlick P J
Published: June 2006

We have developed and validated catheterization protocols in mice that allow for simultaneous infusion and sampling. A sampling catheter was inserted in the lateral vein of the tail, while the animals were infused either intravenously or intragastrically through a second catheter placed in the contralateral lateral vein or via an intragastric catheter, respectively. The applicability of these methods of infusion and blood sampling were validated by conducting urea kinetics utilizing stable isotopes. These non-surgical procedures are non-invasive, inexpensive, fast to perform and animals do not require a recovery period before their use.
Microbiological monitoring of laboratory mice and biocontainment in individually ventilated cages: a field study
Authors: Brielmeier M , Mahabir E , Needham J R , Lengger C , Wilhelm P , Schmidt J
Published: June 2006

Over recent years, the use of individually ventilated cage (IVC) rack systems in laboratory rodent facilities has increased. Since every cage in an IVC rack may be assumed to be a separate microbiological unit, comprehensive microbiological monitoring of animals kept in IVCs has become a challenging task, which may be addressed by the appropriate use of sentinel mice. Traditionally, these sentinels have been exposed to soiled bedding but more recently, the concept of exposure to exhaust air has been considered. The work reported here was aimed firstly at testing the efficiency of a sentinel-based microbiological monitoring programme under field conditions in a quarantine unit and in a multi-user unit with frequent imports of mouse colonies from various sources. Secondly, it was aimed at determining biocontainment of naturally infected mice kept in an IVC rack, which included breeding of the mice. Sentinels were exposed both to soiled bedding and to exhaust air. The mice which were used in the study carried prevalent infectious agents encountered in research animal facilities including mouse hepatitis virus (MHV), mouse parvovirus (MPV), intestinal flagellates and pinworms. Our data indicate that the sentinel-based health monitoring programme allowed rapid detection of MHV, intestinal flagellates and pinworms investigated by a combination of soiled bedding and exhaust air exposure. MHV was also detected by exposure to exhaust air only. The IVC rack used in this study provided biocontainment when infected mice were kept together with non-infected mice in separate cages in the same IVC rack.
Laboratory rearing conditions for improved growth of juvenile Helix aspersa Müller snails
Authors: García A , Perea J M , Mayoral A , Acero R , Martos J , Gómez G , Peña F
Published: June 2006

A laboratory rearing system in semi-controlled conditions is proposed to facilitate the behavioural rhythms of the edible snail ( Helix aspersa) and to produce a high growth rate with low variability. The growth data were used to construct a model for weight estimation based on age. The animals' live weights showed low variability (<17%) and normal distribution. The best model for estimating weight from age is the logistic model, with a high corelation coefficient (>90%), and a high level of significance for the coefficient ( P<0.0001).
Usefulness of whole blood aggregometry and its comparison with thromboxane generation assay in monitoring acetylsalicylic acid effectiveness – a multiparametric study in rats
Authors: Nocun Marek , Golanski Jacek , Lapshina Elena , Zavodnik Leu , Dobaczewski Marcin , Kazmierczak Piotr , Markuszewski Leszek , Zavodnik Ilya , Watala Cezary
Published: June 2006

Clin Chem Lab Med 2006;44:853–62.
Psychological Profile of Chinese with Cleft Lip and Palate Deformities
Authors: Cheung Lim K. , Loh John Ser Pheng , Ho Samuel M. Y.
Published: June 2006

Objective:

To assess the psychological well-being of patients with cleft lip and palate (CLP).

Patients/setting:

Ninety-four Chinese CLP subjects between 10 and 40 years of age were recruited from the Discipline of Oral and Maxillofacial Surgery, The University of Hong Kong, between June and December 2003. They were divided into two groups for comparison: adolescents (10–16 years old) and adults (17– 40 years old). A control group of 116 healthy non-CLP patients was also recruited during the same period.

Interventions:

All CLP and non-CLP patients were asked to complete a set of four questionnaires to assess their psychological status. The questionnaires included the Social Avoidance and Distress Scale, the Satisfaction with Life Scale, the Culture-Free Self-Esteem Inventory, and the Chinese Miller Behavioral Style Scale.

Results:

Chinese CLP patients exhibited levels of subjective well-being and social anxiety that were similar to the published levels of a group of British CLP patients. They also had significantly lower general and social self-esteem but higher parental self-esteem than the non-CLP control group.

Conclusion:

CLP patients were generally satisfied with life and did not exhibit more social anxiety than the non-CLP control group. They also had a good relationship with their parents. Gender and educational level had no influence on their psychological profile. However, these CLP patients had lower self-esteem than non-CLP patients.
Zygomaticotemporal Synostosis: A Rare Cause of Progressive Facial Asymmetry
Authors: Rogers Gary F. , Greene Arin K. , Oh Albert K. , Robson Caroline , Mulliken John B.
Published: June 2006

Cranial synostosis is relatively common; however, premature closure of a facial suture is remarkably rare. We describe an adolescent male with zygomaticotemporal synostosis that manifested as progressive midfacial and orbital asymmetry, angulation of the cranial base, and nasal deviation. To our knowledge, this is the first description of this anomaly in the literature.
Using Diaries to Assess Nonprescription Drug Use among University Students
Authors: Acocella Cecilia M.
Published: June 2006

Nonprescription drug use among university students was investigated using survey and behavioral diary methodologies to assess usage of nonprescription drug use and to compare survey and diary methodologies. Surveys were completed by 183 students (136 females and 47 males) that asked how often they used nonprescription drugs and what those drugs were. Of these participants, 61 (53 females and 8 males) voluntarily completed behavioral diaries for nonprescription drug use for a three week period. Survey data showed 83.1% of participants used nonprescription drugs in the past week, with pain relievers being the most common drug used. There was a significant correlation between the number of times participants reported using nonprescription drugs on the surveys and what the participants reported in their diaries, with no differences in the mean number of uses between survey and diary. This indicates that participants can recall information about their medication-taking behavior with some accuracy. Behavioral diaries were also able to show some of the misuse that is associated with using nonprescription medications. In most cases of misuse, too large a dose was taken. Students should be provided with information about the possible long- and short-term effects of these medications.
A characterization of absolutely monotonic (Δ) functions
Authors: Morillas Mariela
Published: June 2006

Absolutely monotonic (?) function of order n are characterized in terms of n-dimensional totally increasing functions. Applications to n-copulas are presented.
Symbolic Mathematics Programs: A Tool for the Applied Economist
Authors: Gloy Brent A. , Preckel Paul V.
Published: June 2006

The power of the symbolic mathematics program Maple is demonstrated for teaching topics from microeconomics (the benefits of portfolio diversification) and econometrics (a geometric perspective of multicollinearity). In particular, it appears that the use of symbolic mathematics programs has excellent potential to strengthen the development and integration of graphical and algebraic intuition for a wide variety of economic problems.
Academic Opportunities Outside the Land Grant System: Exploring a Niche Market for Agricultural Economics Ph.D. Students
Authors: Hyde Jeffrey , Lovejoy Stephen B.
Published: June 2006

Ph.D. students in agricultural economics, like any other discipline, face great uncertainty when pursuing academic employment. This is particularly true for those who want to pursue a position that is predominantly teaching. In this article, we explore the possibility of obtaining such a position within an economics department at a non‐land grant academic institution. A survey was distributed to nearly 300 economics department chairs or heads at smaller colleges and universities. The results show that although gaining classroom experience of any sort is essential, it is most beneficial for the graduate student to have an independent teaching experience. We recommend that agricultural economics departments implement a mentoring program to guide students in developing their teaching skills.
Getting from Economic Analysis to Policy Advice
Authors: Bonnen James T. , Schweikhardt David B.
Published: June 2006

Economists play several distinct but necessary roles in the process of translating economic knowledge from the discipline to use in policy decisions. Economists engaged in disciplinary research might legitimately deal with more simplified abstractions of economic problems in conducting their research, whereas those engaged in providing policy analysis and advice to policy makers might face different constraints on the types of analysis that can be used by policy makers. In the role of policy analyst or adviser, economists face a number of challenges and risks. Those preparing to engage in such roles should understand (a) the constraints that will be faced in using and communicating economic analysis to policy makers, (b) the limitations of economic theory in addressing policy issues faced by decision makers, and (c) the risks inherent in participating in the policy‐making process. The economist entering the policy process must be prepared to present economic advice in a manner that is easily understood and communicated and be prepared to address dimensions of policy problems that might not comply with the standard assumptions of neoclassical theory. The policy adviser must also be prepared to deal with databases that are often inadequate for decision‐making purposes, time constraints that preclude the completion of a thorough analysis, value dimensions of policy issues that might overrule the results of economic analysis, and the fundamentally different roles of the policy maker and the economic adviser in the decision‐making process.
Tread Depth Effects on Tire Rolling Resistance
Authors: Luchini J. R. , Motil M. M. , Mars W. V.
Published: June 2006

This paper discusses the measurement and modeling of tire rolling resistance for a group of radial medium truck tires. The tires were subjected to tread depth modifications by “buffing” the tread surface. The experimental work used the equilibrium test method of SAE J-1269. The finite element analysis (FEA) tire model for tire rolling resistance has been previously presented. The results of the testing showed changes in rolling resistance as a function of tread depth that were inconsistent between tires. Several observations were also inconsistent with published information and common knowledge. Several mechanisms were proposed to explain the results. Additional experiments and models were used to evaluate the mechanisms. Mechanisms that were examined included tire age, surface texture, and tire shape. An explanation based on buffed tread radius, and the resulting changes in footprint stresses, is proposed that explains the observed experimental changes in rolling resistance with tread depth.
Inverse Design Methodology of a Tire
Authors: Koishi M. , Govindjee S.
Published: June 2006

Most rubber components usually suffer large deformation, thus one should consider finite deformation theories when designing rubber products such as tires. Although finite element analysis (FEA) is useful for computing nonlinear structural response in standard problems, it is more difficult to predict the undeformed original to-be-manufactured shape of a part corresponding to a design constraint involving a prescribed deformed shape under a given load. For example, one can use an optimization technique to predict the original shape in the sense of an inverse problem via successive iteration. As another procedure to solve such inverse problems, Govindjee and Mihalic [4,5] have proposed a new computational procedure to predict undeformed (to-be-manufactured) shapes for prescribed exterior deformed configurations, Cauchy tractions and displacement boundary conditions. In this paper, we demonstrate applications of the inverse shape determination problem for a tire design. The proposed methodology enables us to predict an undeformed (to-be-manufactured) tire shape corresponding to the design constraint of a prescribed exterior deformed configuration. After reviewing the formulation of the inverse shape determination, some numerical examples illustrating the methodology in a tire design are presented.
Multiaxial Fatigue Crack Initiation in Rubber
Authors: Mars W. V.
Published: June 2006

This paper describes a new model for predicting multiaxial fatigue crack initiation in rubber. The work is motivated by a need to predict crack initiation life in tires, based on strain histories obtained via finite element analysis. The new model avoids the need to explicitly include cracks in the finite element model, and applies when the cracks are small compared to the strain gradient. The model links the far-field strain state to the energy release rate of an assumed intrinsic flaw. This is accomplished through a new parameter, the cracking energy density. The cracking energy density is the portion of the total elastic strain energy density that is available to be released on a given material plane. The model includes an algorithm to select the material plane which minimizes the life prediction for a given strain history. The consequences of the theory for simple strain histories are presented, as well as predictions for more complicated histories. The theory is compared with published data, and with new results from recent combined axial/torsion fatigue experiments.
Prediction of Tire Shape Change During Post Cure Inflation
Authors: Kennedy R. H.
Published: June 2006

One step in the tire manufacturing process may be post cure inflation. In this step, the tire is cooled from cure temperature to below the glass transition temperature of the fabric cords while being held at a constant inflation pressure. Due to the thermal effects and creep of the component materials, the shape of the tire will be different after the post cure inflation than before. This change in tire shape from that in the mold drawings should be accounted for in performing finite element analyses to predict tire performance characteristics. This paper describes a modeling methodology that predicts the tire's shape change through the post cure inflation process using the finite element method. This is a complex process to represent analytically, with many different mechanisms contributing to the deformations of the tire. These include thermal expansion/shrinkage of the rubber and cords as they cool, creep of both the rubber and fabric cords, and change in material moduli. Since these mechanical effects are temperature dependent, the model uses results from the thermal history prediction model presented previously. The quality of the modeling process was assessed by comparing predicted to measured dimensions for several tire constructions and sizes. Selected results are presented to show the accuracy of the modeling procedure.
Dynamic Damping and Stiffness Characteristics of the Rolling Tire
Authors: Jianmin G. , Gall R. , Zuomin W.
Published: June 2006

A variable parameter model to study dynamic tire responses is presented. A modified device to measure terrain roughness is used to measure dynamic damping and stiffness characteristics of rolling tires. The device was used to examine the dynamic behavior of a tire in the speed range from 0 to 10 km/h. The inflation pressure during the tests was adjusted to 160, 240, and 320 kPa. The vertical load was 5.2 kN. The results indicate that the damping and stiffness decrease with velocity. Regression formulas for the non-linear experimental damping and stiffness are obtained. These results can be used as input parameters for vehicle simulation to evaluate the vehicle's driving and comfort performance in the medium-low frequency range (0–100 Hz). This way it can be important for tire design and the forecasting of the dynamic behavior of tires.
Vehicle and Course Characterization Process for Indoor Tire Wear Simulation
Authors: Stalnaker D. O. , Turner J. L.
Published: June 2006

An empirical methodology is described for separately characterizing vehicles and road courses for subsequent combination to predict tire force histories in tire use or testing. By building a library of vehicle and wear course characterizations, indoor wear test simulations can be selectively constructed by using any combination of “virtual” test vehicles and wear courses. A reliable transient record of vertical, lateral and fore-aft forces and inclination angles can be generated and supplied to drive the indoor wear tire loading fixture. Vehicle characterization involves mapping the basic dynamic load transfer behavior over a range of acceleration, deceleration and cornering maneuvers. A unique indoor vehicle test facility is described for efficiently capturing the tire forces and inclination angles during various maneuvers. All four tire positions can be characterized. Vehicle center of gravity (CG) accelerations and speeds are also recorded during indoor testing. An alternative to experimental measurements is the use of a vehicle computer model for mapping the basic dynamic load transfer behavior. Empirical equations relating vehicle kinematics to tire forces and inclination angles have been developed and are presented. A method of utilizing these equations together with outdoor wear course measurements for predicting transient tire force histories is presented. The method is demonstrated and validated with several vehicle case studies. The tire force component of a wear course can be characterized by measurement of a few parameters: the vehicle CG accelerations and the longitudinal velocity. Course characterization is illustrated using the Department of Transportation's Uniform Tire Quality Grading wear course in the San Angelo, TX area. The full 650 km course was characterized and combined with the laboratory characterization of a 1997 Pontiac Grand Am. Four 650 km drive files were created, one for each tire position, for an indoor wear machine. These consisted of five time-based parameters: radial load, lateral force, wheel torque (acceleration, deceleration forces), inclination angle, and velocity. By sequencing a tire through these four drive files, it was “rotated” as it would have been on the actual vehicle. Examples of tire wear rates and irregular wear are shown for a number of tire constructions, comparing the indoor to the outdoor results. Good correlation was achieved. This simulation technique permits the tire force spectrum of quite complex and lengthy routes to be accurately reproduced in the precisely controlled environment of the laboratory. Each cornering maneuver, each braking and acceleration event, every hill and town can be reproduced in real-time. Only by combining the specific vehicle dynamics of a given vehicle with that of a specific wear route can tire wear be accurately simulated. This tire-vehicle system simulation methodology is referred to as a TS-Sim model.
A Correlation Between Rolling Tire Contact Friction Energy and Indoor Tread Wear
Authors: Knisley S.
Published: June 2006

In an effort to reduce tire development time and cost, tire companies have developed accelerated indoor wear test technology and are developing modeling methods to conduct tire wear evaluations in a “virtual” sense. Much automotive and tire industry expertise has been devoted to establishing a relationship between outdoor and indoor wear test results. The development of modeling techniques has focused on the prediction of friction energy in rolling tire contact. A successful “virtual” wear test based on this technique requires an objective link between rolling tire contact friction energy and tire wear. In this paper, a correlation equation using experimentally measured rolling contact friction energy and indoor tread wear is obtained for a specific passenger tire construction. Test equipment and methods for rolling contact measurements and indoor tread wear are described. Laser measurements of tread loss are compared to friction energy results for combined straight-ahead rolling and cornering conditions to establish a reasonable correlation between contact friction energy and tire tread loss on a global and local scale across loading conditions representative of a realistic outdoor wear course.
Application of STOM to the Optimal Tire Contour Design by Introducing the Aspiration-level Indicator
Authors: Cho J. R. , Jeong H. S. , Kim N. J. , Kim K. W.
Published: June 2006

Many tire performances are associated with the tire design, among which maneuverability and tire durability become major ones to be considered. The former performance is determined by the tension-value distribution along the sidewall carcass, and the latter by the peak strain energy density in the belt edge region. These two mechanical quantities are closely related to the sidewall carcass contour, so that the above-mentioned two performances could be improved by sidewall contour optimization. Unfortunately, however, this kind of multi-objective optimization requires interactive methods, for which the designer's decision-making is involved, owing to the existence of multi-peaks. In this study, we basically apply the satisficing trade-off method (STOM), but we intend to systemize it more by introducing aspiration-level indicators that control the entire optimization process. Through numerical experiment, we confirm that the proposed refined STOM leads systematically and efficiently to a nearly optimum sidewall contour.
Simplified Approach to Calculating Geometric Stiffness Properties of Tread Pattern Elements
Authors: Okonieski R. E. , Moseley D. J. , Cai K. Y.
Published: June 2006

The influence of tread designs on tire performance is well known. The tire industry spends significant effort in the development process to create and refine tread patterns. Creating an aesthetic yet functional design requires characterization of the tread design using many engineering parameters such as stiffness, moments of inertia, principal angles, etc. The tread element stiffness is of particular interest because of its use to objectively determine differences between tread patterns as the designer refines the design to provide optimum levels of performance. The tread designer monitors the change in stiffness as the design evolves. Changes to the geometry involve many attributes including the number of sipes, sipe depth, sipe location, block element edge taper, nonskid depth, area net-to-gross, and so forth. In this paper, two different formulations for calculating tread element or block stiffness are reviewed and are compared to finite element results in a few cases. A few simple examples are shown demonstrating the basic functionality that is possible with a numerical method.
A Finite Element Tire Model and Vibration Analysis: A New Approach
Authors: Zhang Y. , Palmer T. , Farahani A.
Published: June 2006

A complete finite element tire model was developed for the purposes of vehicle dynamics analyses and full vehicle finite element model real time proving ground simulations. The tire model was validated through simulations of some of the very important global, static and dynamic mechanical properties such as the tire radial and lateral stiffnesses, free-drop test, and low-speed rolling cornering stiffness. The three-dimensional free vibration and harmonic/randomly forced vibrations with ground contact of the tire model were studied here. One of the main purposes for the present study is to provide a new approach toward tire and vehicle NVH studies. All the analyses were nonconventional in the sense that, instead of NASTRAN-type modal analysis, the explicit nonlinear dynamic finite element code LS/DYNA3D was used to conduct all the analyses in the time domain, and the vibration modes were decomposed via fast fourier transformation.
Analytical Model of Tire Cavity Resonance and Coupled Tire/Cavity Modal Model
Authors: Gunda R. , Gau S. , Dohrmann C.
Published: June 2006

The acoustic resonance of the air cavity in the tire/wheel assembly may be a contributor to vehicle interior noise through the structure-borne noise transmission path. This problem has been examined in the past using approximate closed form solutions (based on plane wave theory for a two-tube model) and numerically, using FEA. The coupling between the cavity resonance and structural resonance of the wheel may result in higher levels of interior noise as noted previously.

The two primary goals of this paper are (1) to develop simple analytical models to gain fundamental understanding of some observed phenomena and for a quick estimation of cavity resonance frequency to assist in the design process, and (2) to develop tire modal models incorporating the acoustic cavity to predict coupled system natural frequencies and response.

An improved analytical model for accurate calculation of acoustic cavity resonance frequencies of a static, unloaded tire is developed using variational principles. The sensitivities of the cavity resonance frequencies to tire width and aspect ratio are examined. For the case of a loaded tire, an improved analytical formulation based on plane wave propagation (for linearly varying cross-sectional area) is developed. Deformed structure geometry from FEA is used as input to the analytical model.

The FEA-based methodology used in the tire/cavity coupling analysis is as follows: The tire structural modes are calculated, ignoring the effect of the acoustic cavity. The tire cavity modes are calculated using deformed cavity geometry only. Next, the structural/acoustic coupling matrix is calculated. Finally, a coupled cavity-structure modal model is generated from modal mass and stiffness of the tire/wheel assembly, the cavity modal matrices, and the coupling matrix. This process is an improvement over conventional tire modal models, which only include structural modes.
Relationships Between the Friction and Viscoelastic Properties of Rubber
Authors: Amino N. , Uchiyama Y.
Published: June 2006

In this study, the relationships between friction and viscoelastic properties such as loss tangent tan δ and storage modulusE′ were examined. Wet skid resistance was measured using the British Pendulum Tester. The rubber specimens were rubbed againstfive silicone carbide cloths of differing abrasive grain sizes. The viscoelastic properties of the rubber specimens were measured with a viscoelasticspectrometer. From the data on wet skid resistance and viscoelastic properties, it is found that the coefficient of friction μ varies as follows:

          μ = a + b · tan δ/E′

where a and b are constants. Tan δ/E′ was related to the hysteresis term of friction, and the μ-frequency curves were compared with the tan δ/E′ –frequency curves.