bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation and Use of an Index of Oral Health Status
Authors: Lang W. Paul , Borgnakke Wenche S. , Taylor George W. , Woolfolk Marilyn W. , Ronis David L. , Nyquist Linda V.
Published: April 2007

Objectives: The goals of this investigation were (1) to evaluate the Oral Health Status Index in relation to demographic characteristics, socioeconomic status, and preventive behaviors of an adult population; and (2) to understand how individual index components performed as indicators of oral health status compared to the composite index. Methods: The Oral Health Status Index (OHSI) was used on a probability sample of adults, aged 18–93 years, living in the Detroit tricounty area. Data were collected on 509 subjects via in‐home dental examinations. Bivariate and multivariate analyses were used to compare the OHSI and its components, including decayed, missing, and replaced teeth, free ends, and moderate and severe periodontal disease measures. Results: The mean OHSI score for subjects was 77.3 (se=1.83) with a range of ‐8.0 to 100.0. In regression analyses, OHSI scores were positively correlated with subjects' education level, self‐rated oral health scores, and frequency of dental checkups and negatively correlated with age, nonwhite race, and smoking. Of the index components, missing teeth performed well as an indicator of oral health status. Missing teeth were positively correlated with age, nonwhite race, and smoking and negatively correlated with education level, self‐rated oral health, and use of Medicaid. About 53 percent of variance in OHSI scores was explained by the multivariate models, compared to 46 percent for missing teeth.

Conclusions: Choosing an indicator of oral health status likely will depend upon the characteristics of the population to be studied. As a composite measure of oral health status, the OHSI performed acceptably; however, missing teeth, an index component, also worked well. Continued evaluation of the OHSI is warranted.
Type 1 Diabetes Mellitus and Oral Health: Assessment of Tooth Loss and Edentulism
Authors: Moore Paul A. , Weyant Robert J. , Mongelluzzo Mary Beth , Myers Daniel E. , Rossie Karen , Guggenheimer James , Hubar Heidi , Block Harvey M. , Orchard Trevor
Published: April 2007

Objective: The oral health of an adult population previously diagnosed with juvenile onset insulin dependent‐diabetes was comprehensively assessed. The goal of this exploratory cross‐sectional evaluation was to describe the characteristics related to partial tooth loss and edentulism in subjects with Type 1 diabetes mellitus. Methods: An adult population of 406 Type 1 diabetes mellitus subjects, who had been monitored for 6–8 years as part of a University of Pittsburgh longitudinal study of medical complications associated with diabetes, received an oral health examination for missing teeth, edentulism, coronal and root caries, periodontal status, and oral health behaviors. Results: Of the 406 subjects evaluated, 204 had no missing teeth, 186 had partial tooth loss (1–27 missing teeth), and 16 were edentulous. Patients who had partial tooth loss or who were edentulous were generally older; had lower incomes and levels of education; and had higher rates of nephropathy, neuropathy, retinopathy, and peripheral vascular disease. A logistic regression model found partial tooth loss to be significantly associated with extensive periodontal disease in remaining teeth (OR=7.35), a duration of diabetes longer than 24 years (OR=5.32), not using dental floss (OR=2.37), diabetic neuropathy (OR=2.29), household income less than $20,000 (OR=2.21), multiple coronal caries and fillings (OR=1.98), and bleeding on probing (OR=1.82). Conclusion: Although the majority of these adult Type 1 diabetes patients had serious medical complications associated with their diabetes, the possible impact of diabetes mellitus on oral health should be included in their overall management.
Economic Evaluation of a Pit and Fissure Dental Sealant and Fluoride Mouthrinsing Program in Two Nonfluoridated Regions of Victoria, Australia
Authors: Morgan Mike V. , Crowley Steven J. , Wright Clive
Published: April 2007

Objectives: This study assessed the cost effectiveness of a three‐year school‐based pit and fissure dental sealant and fluoride mouthrinsing program in two nonfluoridated regions in Victoria, Australia. Methods: The analysis was based on a community intervention in five schools comparing an intervention group receiving the pit and fissure dental sealant, a weekly fluoride mouthrinsing, and an annual oral hygiene education session, with a control group receiving oral hygiene education only. The study measured mean differences in DMFS increments between study groups. Results: The mean discounted DMFS difference in increment (DMFS avoided) between study groups was 1.22 DMFS over three years. The incremental cost‐effectiveness ratio comparing intervention to control group varied between a net savings of $7.00 to a cost of $35.60 per DMFS avoided, depending on assumptions used in the analysis. Results were sensitive to assumptions on program effectiveness, dental examination rates, and baseline DMFS of students. The program became more cost effective with each successive year of the program. Conclusion: The introduction of such a preventive program in nonfluoridated regions of Victoria will represent an efficient use of community resources. Policy issues that need consideration include whether to target areas where adolescents have a history of high dental disease experience, and whether dentists or auxiliaries are used as service providers. The need exists for a systematic evaluation (including an economic evaluation component) of dental prevention and treatment programs in Australia.
Dental Caries and Dental Fluorosis Among Schoolchildren Who Were Lifelong Residents of Communities Having Either Low or Optimal Levels of Fluoride in Drinking Water
Authors: Selwitz Robert H. , Nowjack‐Raymer Ruth E. , Kingman Albert , Driscoll William S.
Published: April 2007

Objective: This paper reports findings for dental caries and dental fluorosis in 8–10‐ and 13–16‐year‐old schoolchildren who were lifelong residents of communities having either naturally occurring low (Broken Bow and Holdrege, NE; <0.3 ppm) or optimal (Kewanee, IL; 1 ppm) levels of fluoride in drinking water. Methods: Findings are reported for participants who received both dental caries and dental fluorosis examinations (n=495). The DMFS and TSIF indices, respectively, were used to assess dental caries and dental fluorosis. Results: The mean DMFS score adjusted for age, sealant presence, and fluoride use was significantly lower in Kewanee (1.8) than was the adjusted mean caries score in either Holdrege (2.9) or Broken Bow (3.6). Adjusted mean DMFS scores in Broken Bow and Holdrege were not statistically different. The mean percent of fluorosed tooth surfaces per person, adjusted for age and use of dietary fluoride supplements, was similar in the three communities (approximately 15%); more than 80 percent of tooth surfaces in all participants were fluorosis‐free. Conclusion: Findings from the present study suggest that water fluoridation still is beneficial and that dental sealants can play a significant role in preventing dental caries. In addition, findings from this survey appear to support the premise that the difference in dental fluorosis prevalence between fluoridated and nonfluoridated communities has narrowed considerably in recent years.
Oral Functional Limitation among Dentate Adults
Authors: Foerster Ulrich , Gilbert Gregg H. , Duncan R. Paul
Published: April 2007

Objectives: The purpose of this study was to measure the prevalence of oral functional limitation in adults and to identify clinical and sociodemographic factors associated with that limitation. Methods: The Florida Dental Care Study is a longitudinal study of risk factors for changes in oral health. Subjects (n=873) with at least one tooth who were 45 years old or older participated in a baseline in‐person interview and dental examination. Subjects were queried about oral functional limitations. Results: Twenty‐three percent of subjects reported difficulty chewing one or more foods using a five‐item chewing index, and 10 percent reported difficulty speaking or pronouncing words because of problems with the mouth. The covariates in a multiple logistic regression identified as being significantly associated with chewing difficulty were fewer pairs of occluding anterior teeth, fewer pairs of occluding posterior teeth, more posterior teeth that are root tips, more anterior teeth that are mobile, reporting tooth pain, reporting bad breath, having but not wearing prosthetic appliances, reporting dry mouth, and being female. Having fewer anterior teeth, reporting a sore and/or broken denture, reporting unattractive teeth, and being black were significantly associated with speaking difficulty/difficulty pronouncing words because of problems with the teeth, mouth, or dentures. Conclusion: The findings in this study suggest a significant prevalence of oral functional limitation in dentate adults. Certain clinical and sociodemographic factors were strongly and independently associated with its presence.
Descriptive Models of Restorative Treatment Decisions
Authors: Bader James D. , Shugars Daniel A.
Published: April 2007

Objectives: This study developed descriptive models of dentists' restorative treatment decisions for individual teeth. Such models could be useful in personnel planning, in assessing the effects of dental treatment programs, and in furthering understanding of dentists' decision‐making processes. Methods: Logistic regression was used to construct models of the probability of individual teeth receiving a recommendation for restorative treatment. Independent variables for the models were data from epidemiologic oral examinations and self‐administered questionnaires of subjects who were seeking treatment at a dental school. Data for the dependent variable, the probability of treatment, were collected from multiple dentists' treatment plans of these subjects. Separate models were constructed for molar, premolar, and anterior teeth. An assessment of the models' utilities in a different population consisted of comparing the treatment probabilities estimated by the models with those actually experienced by a community sample of 317 individuals who visited dentists in the 18 months following our examination. Results: Constructed models for molar, premolar, and anterior teeth returned kappa values of 0.60, 0.62, and 0.65, respectively, for the original data set. The models were less accurate in identifying which teeth received treatment among subjects in the community sample, with kappas of 0.10, 0.18, and 0.20, respectively. Conclusion: Models of dentists' restorative treatment decision making based on clinical and nonclinical data can determine the probability of treatment for individual teeth with reasonable accuracy. Hence, the approach holds promise for developing measures of normative treatment need. However, the models are not accurate predictors of dichotomous decisions by individual dentists regarding treatment interventions. Both differences in the subject samples used to develop and assess the models and individual dentist idiosyncrasies may contribute to this inaccuracy.
Colonization of Mutans Streptococci in 8‐ to 15‐month‐old Children
Authors: Karn Thomas A. , O'Sullivan David M. , Tinanoff Norman
Published: April 2007

Objective: The age at which a child becomes colonized with mutans streptococci (MS) is important for understanding early childhood caries. The aim of this study was to explore the relationship of age with MS colonization in infants. Methods: Inner‐city children (n=149) between the ages of 8 months and 15 months, inclusive, who reportedly were still using a baby bottle, were sampled for MS. Results: Evidence of MS colonization was seen as early at 10 months of age. For children 12 months old or younger (n=80), 25 percent had detectable levels of MS; in the 15‐month age group, 60 percent were colonized. Conclusion: This study suggests that prevention of MS colonization in some populations may need to be initiated prior to the child's first birthday.
Can Questionnaires Replace Clinical Surveys to Assess Dental Treatment Needs of Adults?
Authors: Robinson Peter G. , Nadanovsky Paulo , Sheiham Aubrey
Published: April 2007

Objective: The purpose of this study was to ascertain whether questionnaires can be used to replace clinical surveys by comparing normative and perceived caries status and treatment needs in a sample of adults living in East London, UK. Methods: A cross‐sectional study was conducted in two stages: a structured interview inquired about perceived dental caries status and treatment needs, and dental examinations were performed to determine oral health status and normative treatment needs. Perceived and normative assessments were compared for overall proportions, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV), using the dental examination as a gold standard. Results: Of 139 people examined, 122 were dentate. The PPVs for perceived caries and treatment need were 0.58 and 0.67, respectively. Overall agreement was 65.4 percent for the presence of caries and 64.7 percent for the presence of treatment need. However, no net error was found between the proportions of participants with decay, and a small net error (7.4%) was found between perceived and normative treatment need. Conclusion: Self‐assessment is not useful to assess individual dental treatment need, but is of possible value in assessing the needs of adult communities.
Clinical Sealant Retention Following Two Different Tooth‐cleaning Techniques
Authors: Gillcrist James A. , Vaughan Michelle P. , Plumlee George N. , Wade George
Published: April 2007

Objectives: This study compared the effectiveness of two different tooth‐cleaning techniques on clinical sealant retention. Methods: Seventy‐four children in second and third grades at an elementary school in the rural town of Waverly, Tennessee, had sealants applied to four, noncarious, fully erupted, first permanent molar teeth. The teeth had been cleaned using a brush attached to a rotary instrument with fluoridated prophy paste, versus a toothbrush without paste (dry brushing). A split‐mouth design was used, whereby one side (upper and lower) of the mouth was subject to one tooth‐cleaning technique while the opposite side received the other technique. Results: Twelve months after a single application of pit and fissure sealant, 63 children were available for recall. Exactly 252 teeth were examined and overall retention was high, with approximately 98 percent of sealants retained. Although the greatest loss of sealant occurred with the rotary instrument technique, the difference in proportions of missing sealant between techniques was not statistically significant. Conclusion: In this study, the tooth‐cleaning technique of dry brushing with a toothbrush as a preparatory step in the sealant procedure yielded high clinical sealant retention at 12 months. This retention was comparable to that observed with rotary instrumentation. This finding suggests that dry brushing by the operator may be an acceptable alternative to using a rotary instrument with brush and paste.
Fluoride Varnish: a Useful New Tool for Public Health Dentistry
Authors: Bawden James W.
Published: April 2007

Since first shown to be effective by Bibby in 1942, professionally applied topical fluorides have been used successfully as a caries‐preventive intervention. In the United States, the acidulated phosphate fluoride (APF) gels have been the most widely used agent for over two decades. While effective, APF has several practical disadvantages, including unpleasant taste and the risk of fluoride overingestion. The use of APF on infants and very young children is not practical or safe. Recently, flloride varnish has become available in the United States. It has been used widely in Europe and Scandinavia for 25 years. Its effectiveness and safety are documented in over 50 clinical trials. Fluoride varnish is easy to apply, is well accepted by children, and eliminates the risk of overingestion of fluoride. Fluoride varnish is approved by the FDA as a “device” and must be used “off label” for the prevention of caries. Because of the large body of published data documenting its effectiveness and safety, there is no legal risk in using fluoride varnish off label. In fact, the American Dental Association has granted its seal of approval to Duraphat®, one of the varnish products. Varnish offers considerable advantages in the dental public health setting. Of particular note, it is practical and safe to apply to the teeth of infants and very young children.
Incidence of Orofacial Injuries in High School Sports
Authors: Kvittem Brent , Hardie Nancy A. , Roettger Mark , Conry John
Published: April 2007

Objectives: This study determined the incidence of orofacial injuries in athletes attending seven neighboring Minnesota high schools who participated in varsity soccer, wrestling, and basketball during the 1996–97 academic year. Methods: Incidence was determined through athletes' written surveys and athletic trainer records. Results: Survey response rates ranged from 86.3 percent to 94.0 percent among schools for all sports. The incidence rate of at least one orofacial injury per athlete in a season was 27.6 percent (SD=20.2) in soccer, 72.3 percent (SD=9.3) in wrestling, and 55.4 percent (SD=23.9) in basketball. Ten percent of athletes sustained dental injuries. Fixed orthodontic appliances posed a higher risk for sustaining an injury in all sports. The games‐to‐practices ratios for injuries were 6.8 (soccer), 1.2 (wrestling), and 1.8 (basketball). Half of the athletes believed mouthguards prevent injuries; however, only 6 percent of the athletes reported mouthguard use. Athletic trainers reported eight orofacial injuries. Conclusion: The substantial rate of orofacial injuries among high school athletes participating in soccer, wrestling, and basketball needs to be minimized. Dentists should ask their adolescent patients routinely about sports participation. Policies should be developed to require school officials to report orofacial injuries, to inform athletes of their risk for orofacial injuries, and to consider mandated mouthguard use for these athletes.
Vitamin B1 (thiamine) uptake by human retinal pigment epithelial (ARPE‐19) cells: mechanism and regulation
Authors: Subramanian Veedamali S. , Mohammed Zainab M. , Molina Andres , Marchant Jonathan S. , Vaziri Nosratola D. , Said Hamid M.
Published: April 2007

Retinal abnormality and visual disturbances occur in thiamine‐responsive megaloblastic anaemia (TRMA), an autosomal recessive disorder caused by mutations in the human thiamine transporter‐1 (hTHTR‐1). Human retinal pigment epithelial cells play a pivotal role in supplying thiamine to the highly metabolically active retina but nothing is known about the mechanism, regulation or biological processes involved in thiamine transport in these cells. To address these issues, we used human‐derived retinal pigment epithelial ARPE‐19 cells to characterize the thiamine uptake process. Thiamine uptake is energy‐ and temperature‐dependent, pH‐sensitive, Na+‐independent, saturable at both the nanomolar (apparent Km, 30 ± 5 nm) and the micromolar (apparent Km, 1.72 ± 0.3 μm) concentration ranges, specific for thiamine and sensitive to sulfhydryl group inhibition. The diuretic amiloride caused a concentration‐dependent inhibition in thiamine uptake, whereas the anti‐trypanosomal drug, melarsoprol, failed to affect the uptake process. Both hTHTR‐1 and hTHTR‐2 are expressed in ARPE‐19 cells as well as in native human retinal tissue with expression of the former being significantly higher than that of the latter. Uptake of thiamine was adaptively regulated by extracellular substrate level via transcriptionally mediated mechanisms that involve both hTHTR‐1 and hTHTR‐2; it was also regulated by an intracellular Ca2+–calmodulin‐mediated pathway. Confocal imaging of living ARPE‐19 cells expressing TRMA‐associated hTHTR‐1 mutants (D93H, S143F and G172D) showed various expression phenotypes. These results demonstrate for the first time the existence of a specialized and regulated uptake process for thiamine in a cellular model of human retinal pigment epithelia that involves hTHTR‐1 and hTHTR‐2. Further, clinically relevant mutations in hTHTR‐1 lead to impaired cell surface expression or function of the transporter in retinal epithelial ARPE‐19 cells.
Selective action of noradrenaline and serotonin on neurones of the spinal superficial dorsal horn in the rat
Authors: Lu Yan , Perl Edward R.
Published: April 2007

The superficial dorsal horn of the spinal cord (SDH; laminae I and II) receives strong input from thin primary afferent fibres and is involved in nociception, pain, temperature sensing and other experiences. The SDH also is the target of serotonergic and adrenergic projections from the brain stem. The interaction between descending pathways that utilize particular mediators and the neurone population of the SDH is poorly understood. To explore this issue, in rat spinal cord slices during whole‐cell recordings from identified SDH neurones, noradrenaline (NA) or serotonin (5HT) were briefly applied in the superfusing artificial cerebrospinal fluid. The action of these agents proved specifically related to the type of SDH neurone and its dorsal‐root afferent input. Vertical, radial and tonic central lamina II cells consistently expressed outward current to both NA and 5HT, but transient central and Substance P (SP)‐insensitive lamina I cells were unaffected directly by either NA or 5HT. Extended islet cells responded with outward current to NA and inward current to 5HT. Lamina I SP‐sensitive cells expressed an outward current regularly to NA. 5HT had inhibitory effects on Aδ and C fibre input to all types of SDH neurones. NA inhibited C fibre input to transient central neurones. The present results support the idea that descending systems may have multiple functions, including but not limited to nociceptive modulation.
On the physiological roles of PIP2 at cardiac Na+–Ca2+ exchangers and KATP channels: a long journey from membrane biophysics into cell biology
Authors: Hilgemann Donald W.
Published: April 2007

Over the last 10 years we have tried to understand the roles of PIP2 in regulating cardiac Na+–Ca2+ exchangers and KATP K+ channels, both of which are directly activated by PIP2. Up to now, the idea that hormones might physiologically regulate these mechanisms by causing changes of PIP2 concentrations in the cardiac sarcolemma, either locally or globally, is not well supported. In intact myocardium, but not excised patches, phosphatidylinositol 4‐phosphate 5‐kinase (PIP5K) activity appears to be Ca2+ activated and dependent on cardiac activity. Potentially therefore the primary second messenger of the heart, cytoplasmic Ca2+, may regulate PIP2 and therewith numerous cardiac membrane processes. In general, however, PIP2 may simply serve to strongly activate various cardiac channels and transporters when they are inserted in the sarcolemma, while a lack of PIP2 on internal membranes maintains transporters and channels inactive during trafficking and processing. As in most, if not all, strong regulatory systems of cells, the activating effects of PIP2 can apparently be countered by strong inactivation mechanisms. In this context, our recent work suggests that internalization of cardiac Na+–Ca2+ exchangers is promoted by increased PIP2 synthesis, especially in combination with other cell signals. Assuming that multiple adapter–PIP2 interactions are necessary to initiate the budding of individual membrane vesicles, the dependence of endocytosis on PIP2 in the surface membrane can potentially be a very steep function. Thus, a better understanding of the regulation of cardiac lipid kinases may be key to understanding when and how cardiac ion transporters and channels are internalized.
PPARδ expression is influenced by muscle activity and induces slow muscle properties in adult rat muscles after somatic gene transfer
Authors: Lunde Ida G. , Ekmark Merete , Rana Zaheer A. , Buonanno Andres , Gundersen Kristian
Published: April 2007

The effects of exercise on skeletal muscle are mediated by a coupling between muscle electrical activity and gene expression. Several activity correlates, such as intracellular Ca2+, hypoxia and metabolites like free fatty acids (FFAs), might initiate signalling pathways regulating fibre‐type‐specific genes. FFAs can be sensed by lipid‐dependent transcription factors of the peroxisome proliferator‐activated receptor (PPAR) family. We found that the mRNA for the predominant muscle isoform, PPARδ, was three‐fold higher in the slow/oxidative soleus compared to the fast/glycolytic extensor digitorum longus (EDL) muscle. In histological sections of the soleus, the most oxidative fibres display the highest levels of PPARδ protein. When the soleus muscle was stimulated electrically by a pattern mimicking fast/glycolytic IIb motor units, the mRNA level of PPARδ was reduced to less than half within 24 h. In the EDL, a three‐fold increase was observed after slow type I‐like electrical stimulation. When a constitutively active form of PPARδ was overexpressed for 14 days in normally active adult fibres after somatic gene transfer, the number of I/IIa hybrids in the EDL more than tripled, IIa fibres increased from 14% to 25%, and IIb fibres decreased from 55% to 45%. The level of succinate dehydrogenase activity increased and size decreased, also when compared to normal fibres of the same type. Thus PPARδ can change myosin heavy chain, oxidative enzymes and size locally in muscle cells in the absence of general exercise. Previous studies on PPARδ in muscle have been performed in transgenic animals where the transgene has been present during muscle development. Our data suggest that PPARδ can mediate activity effects acutely in pre‐existing adult fibres, and thus is an important link in excitation–transcription coupling.
A Fast and Effective Method for Transient Thermoelastic Displacement Analyses
Authors: Liu Shuangbiao , Rodgers Michael J. , Wang Qian , Keer Leon M.
Published: April 2007

Frictional heating due to the relative motion of contacting surfaces causes temperature rise and thermal distortion, which in turn affects the contact geometry and pressure distribution. A fast and effective method is presented for the calculation of the normal surface displacement of an elastic halfspace due to arbitrary transient surface heating. The method uses Fourier-transformed Green’s functions (frequency response functions), found in the closed form by using the approach of Seo and Mura and the heat conduction analyses of Carslaw and Jaeger. The frequency response functions are shown analytically to be the frequency domain representations of the Green’s functions given by Barber. The formulation for the surface normal displacement is in the form of three-dimensional convolution integrals (over surface and time) of the arbitrary transient heat flux and the Green’s functions. Fourier transforms of these convolution integrals are taken, avoiding the Green’s-function singularities and giving a simple multiplication between the transformed heat flux and the (known) frequency response functions. The discrete convolution–fast Fourier transform (DC-FFT) algorithm is applied for accurate and efficient calculations of the normal surface displacement from the frequency response functions for an arbitrary transient heat input. The combination of the frequency-domain formulation and the DC-FFT algorithm makes the solution of transient thermoelastic deformation extremely fast and convenient.
Wear Evaluation and Ranking of Tribomaterials Using a Hasse Diagram Approach
Authors: Sehgal Rakesh , Gandhi O. P. , Angra S.
Published: April 2007

A procedure is developed to evaluate and rank tribomaterials based on wear parameters using a vectorial approach. The method known as the Hasse Diagram approach allows one to graphically compare tribomaterials based on a large number of wear parameters or test results which might otherwise be very confusing. The inclusion of uncertainty and a provision to include weighting factors so that the ranking scheme does not change when additional tribomaterials are added have also been discussed. An example of eight tribomaterials has been presented for ranking based on five wear parameters.
Analysis of Material Transfer From a Soft Workpiece to a Hard Tool: Part II—Experimental Verification of the Proposed Lump Growth Model
Authors: de Rooij M. B. , Schipper D. J.
Published: April 2007

In this study, the lump growth model, described in an accompanying paper (de Rooij and Schipper, 2000) is validated by means of experiments performed on a deepdrawing simulator. In the experiments, the influence of material and roughness properties of both sheet and tool on the galling behavior is determined. For these experiments, a deepdrawing simulator and a selection of aluminum and zinc coated sheets with several (coated) deepdrawing tools are used. Good agreement is found between results of the lump growth model and the sheet metal forming experiments.
Numerical Study of a Rotary Lip Seal With a Quasi-Random Sealing Surface
Authors: Shi Fanghui , Salant Richard F.
Published: April 2007

In all previous numerical simulations of the rotary lip seal, the sealing surface was modeled by regular periodic structures. In the present study, a more realistic quasirandom surface is used. A mixed elastohydrodynamic analysis is used to generate predictions of such seal operating characteristics as friction coefficient, reverse pumping rate, film thickness distribution, hydrodynamic and contact pressure distributions, contact area, and cavitation area. The results are in qualitative agreement with previous experimental observations. In the course of the simulations, a new physical mechanism of reverse pumping has been identified.
Optimal Design of HDD Air-Lubricated Slider Bearings for Improving Dynamic Characteristics and Operating Performance
Authors: Kang Tae-Sik , Choi Dong-Hoon , Jeong Tae-Gun
Published: April 2007

Flying attitudes of the slider, which are flying height, pitch, and roll, are affected by air-flow velocity, skew angle, and manufacturing tolerances. In the traditional design process of air-bearing surfaces, we have considered only the steady state flying attitude over the recording band. To reduce the flying height variation during track seek as well as in steady state, we design a new shape for air-bearing surfaces. An optimization technique is used to improve the dynamic characteristics and operating performance of the new air-bearing surface shapes. The quasistatic approach is used in the numerical simulation of the track seek operation because the skew angle effect dominates the inertial effect even at high seek velocities. The perturbation method is applied to the lubrication equation to obtain the air-bearing stiffness. We employ the method of modified feasible directions and use the weighting method to solve the multicriteria optimization problem. The optimally designed sliders show enhanced flying and dynamic characteristics. The steady state flying heights are closer to the target values and the flying height variations during track seek operation are smaller than those for the original ones. The pitch and roll angles are kept within suitable ranges over the recording band during track seek operation as well as in steady state. The air-bearing stiffnesses of the optimally designed sliders are larger than those of the original ones.
Vapor-Phase Lubrication in Combined Rolling and Sliding Contacts: Modeling and Experimentation
Authors: Sawyer W. Gregory , Blanchet Thierry A.
Published: April 2007

The in situ vapor-phase lubrication of M50 steel, in combined rolling and sliding contacts at 540°C using nitrogen atmospheres containing acetylene, is achieved. Acetylene partial pressures of 0.05 atmospheres are capable of providing continuous lubrication to combined rolling and sliding contacts through pyrolytic carbon deposition. In these tests, friction coefficients as low as μ=0.01 are found for contacts at 2.0 m/s rolling speed, 10 cm/s sliding speed, 100 N load (1.3 GPa Hertzian contact pressure), and ambient temperature of 540°C, with even lower values observed at more modest sliding speeds. One example of a model for vapor phase lubrication of combined rolling and sliding contacts is developed which predicts the lubricant steady-state fractional coverage of the contact surfaces, and from this makes friction coefficient predictions using a linear rule-of-mixture. Friction coefficient responses to step changes in acetylene partial pressure, sliding speed, and disk wear-track diameter are measured. Increased partial pressure of acetylene and increased area available for deposition are observed to be beneficial, while increased sliding speed is detrimental to lubrication performance. Shapes and trends of steady-state friction coefficient versus acetylene partial pressure, sliding speed, and disk wear-track diameter are described and curve-fit by the model. In combined rolling and sliding this example model predicts large regions of operating conditions over which friction coefficient is independent of rolling speed, as well as regions of independence of vapor partial pressure. In the special case of pure sliding, a region of friction coefficient independence of a ratio of partial pressure to sliding speed and another region of independence of a ratio of partial pressure to the product of sliding speed and normal load are predicted.
An Engineering Approach to Non-Hertzian Contact Elasticity—Part II
Authors: Houpert Luc
Published: April 2007

Roller/race misalignment and deformation are used for calculating analytically the pressure distribution along the roller/race contact and the final roller/race load and moment. Use is made of the surface crowns and race undercuts for calculating contact dimensions with their possible truncations at large misalignment or loads. The pressure distribution is not symmetrical when misalignment occurs. This analytical development was possible by using a slicing technique in which the local roller/race geometrical interference was calculated in each slice of the contact. A mix of point and line contact Hertzian solutions developed in a companion paper “Part I” is used for obtaining the final load per slice. The final analytical solutions (load, moment and pressure) are successfully compared to two numerical solutions described briefly. The analytical model has been slightly fine-tuned using correction factors obtained by curve-fitting for matching the results to the numerical ones. In the curve-fitting, the single radius profile and multi-radius profile are distinguished.
Nanomechanical Properties of Polymers Determined From Nanoindentation Experiments
Authors: Klapperich C. , Komvopoulos K. , Pruitt L.
Published: April 2007

The nanomechanical properties of various polymers were examined in light of nanoindentation experiments performed with a diamond tip of nominal radius of curvature of about 20 μm under conditions of maximum contact load in the range of 150–600 μN and loading/unloading rates between 7.5 and 600 μN/s. The elastic modulus of each polymer was determined from the unloading material response using the compliance method, whereas the hardness was calculated as the maximum contact load divided by the corresponding projected area, obtained from the known tip shape function. It is shown that while the elastic modulus decreases with increasing indentation depth, the polymer hardness tends to increase, especially for the polymers possessing amorphous microstructures or less crystallinity. Differences in the material properties, surface adhesion, and time-dependent deformation behavior are interpreted in terms of the microstructure, crystallinity, and surface chemical state of the polymers. Results obtained at different maximum loads and loading rates demonstrate that the nanoindentation technique is an effective method of differentiating the mechanical behavior of polymeric materials with different microstructures.
Stability of Flexibly Supported Oil Journal Bearings Using Non-Newtonian Lubricants: Linear Perturbation Analysis
Authors: Raghunandana K. , Majumdar, and B. C. , Maiti R.
Published: April 2007

The purpose of this paper is to study the effect of non-Newtonian lubricant on the stability of oil film journal bearings mounted on flexible support using linear perturbation technique. The model of non-Newtonian lubricant developed by Dien and Elrod is taken into consideration. The dynamic co-coefficients are calculated for different values of power law index and length to diameter ratio. These are then used to find stability margin for different support parameters to study the effect of the non-Newtonian lubricant.
Thermo-Elastohydrodynamic Analysis of Connecting Rod Bearing in Internal Combustion Engine
Authors: Kim Byung-Jik , Kim Kyung-Woong
Published: April 2007

A comprehensive method of thermo-elastohydrodynamic lubrication analysis for connecting rod bearings is proposed, which includes thermal distortion as well as elastic deformation of the bearing surface. Lubrication film temperature is treated as a time-dependent, two-dimensional variable which is averaged over the film thickness, while the bearing temperature is assumed to be time-independent and three-dimensional. It is assumed that a portion of the heat generated by viscous dissipation in the lubrication film is absorbed by the film itself, and the remainder flows into the bearing structure. Mass-conserving cavitation algorithm is applied, and the effect of variable viscosity is included in the Reynolds equation. Simulation results of the connecting rod bearing of an internal combustion engine are presented. It is shown that the predicted level of the thermal distortion is as large as that of the elastic deformation and the bearing clearance, and that the thermal distortion has remarkable effects on the bearing performance. Therefore, the thermo-elastohydrodynamic lubrication analysis is strongly recommended to predict the performance of connecting rod bearings in internal combustion engines.
Identification of Boundary Forces in Beams From Measured Displacements
Authors: Chesne S. , Pezerat C. , Guyader J. L.
Published: April 2007

This paper deals with shear force and bending moment identification in a beam from measured displacement. The proposed approach, using the weak form of the equation of motion, is based on the extraction of shear force or bending moment from integral equation and choice of test functions, associated to each boundary quantity of interest. After the theorical description, numerical simulation results are shown in order to clarify limits of the method and to stress its self-regularization. Two experimentations are described, showing very good accuracy of shear force and bending moment reconstruction in comparison with direct measurements.
Residual Vibration Suppression for Duffing Nonlinear Systems With Electromagnetical Actuation Using Nonlinear Command Shaping Techniques
Authors: Chen Kuo-Shen , Yang Tian-Shiang , Yin Jui-Feng
Published: April 2007

Residual vibration control is crucial for numerous applications in precision machinery with negligible damping such as magnetically actuated systems. In certain magnetically actuated applications, the systems could also be highly nonlinear and conditionally stable. Although traditional command shaping techniques work well for linear and weakly nonlinear systems, they show little effects for dealing with systems with both strong structural and actuation nonlinearities. In this paper, a general input shaper design methodology for single degree of freedom systems with both Duffing spring and electromagnetic forcing nonlinearities is successfully devised using an energy approach. Following this method, two-step and three-step shapers are developed, which in the linear limit reduce to the traditional zero-vibration (ZV) and zero-vibration-and-derivative (ZVD) shapers, respectively. The robustness of these nonlinear shapers is investigated numerically through several case studies and the results show that the three-step shaper is sufficiently robust to resist significant amounts of parameter variations without exciting significant residual vibration. The two-step shaper, however, is somewhat less robust with respect to parameter variations. Meanwhile, an electromagnetically driven Duffing mechanical system is also constructed so that the performances and robustness of the nonlinear shapers in vibration suppression can be examined. It is shown that the nonlinear shapers result in a significant improvement in residual vibration suppression and settling time reduction in comparison with the traditional linearized ZV and ZVD shapers.
Bulk Reaction Modeling of Sound Propagation Through Circular Dissipative Ducts Backed by an Air Gap
Authors: Kakoty Sashindra K. , Roy Vinay K.
Published: April 2007

Circular and annular dissipative ducts are extensively used for attenuation of sound in industrial applications. In most of the cases the characteristics of lining material is considered to be locally reacting, although; it may not be true always. This is because there are not many investigations available for bulk reaction modeling of circular and annular ducts. The present paper deals with a generalized formulation of a sound wave with mean and induced flow for bulk reaction approach, which can analyze sound attenuation and phase speed in circular and annular cross-section ducts. In the absence of extensive experimental data, the present theoretical model is validated by comparing a few sets of results with some published experimental results. The theoretical results are presented for various parameters of duct and lining material. More emphasis has been given to the effect of the air gap between the lining and rigid wall on the rate of attenuation and phase speed. It has been demonstrated through various sets of results that the air gap between the lining and rigid wall has a great effect on the overall performance of dissipative ducts. The present model can be used to analyze the sound field in air conditioning ducts and other similar applications.
Dynamic Analysis and Parameter Identification of a Single Mass Elastomeric Isolation System Using a Maxwell-Voigt Model
Authors: Zhang Jie , Richards Christopher M.
Published: April 2007

Dynamic analysis and parameter identification of a single mass elastomeric isolation system represented by a Maxwell-Voigt model is examined. Influences that the stiffness and damping values of the Maxwell element have on natural frequency, damping ratio, and frequency response are uncovered and three unique categories of Maxwell-type elements are defined. It is also shown that Voigt and Maxwell-Voigt models with equivalent natural frequencies and damping ratios can have considerably different frequency response spectra. Lastly, a parameter identification method is developed for identifying Maxwell-Voigt models from frequency response spectra. The method is based on constant natural frequency and damping ratio curves generated from modal analysis of potential Maxwell-Voigt models.
Detecting Shaft-to-Seal Rubbing in Power Generation Turbines With the Acoustic Emission Technology
Authors: Leahy M. , Mba D. , Cooper P. , Montgomery A. , Owen D.
Published: April 2007

This paper presents results of an investigation to assess the potential of the acoustic emission (AE) technology for detecting seal-to-rotor rubbing in power generation turbines. The experimental program involved inducing rubs at various axial locations along a 412ton test rotor, rotating at 3000rpm and supported by 7in.(178mm) journal bearings. Whilst there was no change in vibration levels throughout the tests, bearing mounted AE transducers successfully detected all rubbing induced on the rotor.
Hydrofoil Leading Edge Isolation for Vibration and Noise Reduction in Marine Systems
Authors: Brungart Timothy A. , Myer Eric C. , Capone Dean E. , Campbell Robert L. , Petrie Howard L.
Published: April 2007

A technique for reducing the vibration and noise from hydrofoils subject to unsteady lift is examined experimentally. Since the unsteady lift is known to be concentrated in the leading edge vicinity, a single-stage vibration isolation mount is integrated into a hydrofoil near its leading edge to inhibit the leading edge-generated unsteady forces from being transmitted to the remainder of the foil and any structures coupled to it. A single layer of elastomer forms the mount and is used to isolate the leading 20% chord of the hydrofoil from the remainder of the structure. The hydrofoil is excited into vibration by turbulence from an upstream wake generator in a water tunnel facility. Compared to a nonisolated hydrofoil, vibration reductions up to 10dB in level are recorded on the portion of the hydrofoil isolated from the leading edge.
Vibration of Pre-stressed Laminated Sandwich Plates With Interlaminar
Imperfections
Authors: Chakrabarti Anupam , Topdar Pijush , Hamid Sheikh Abdul
Published: April 2007

The vibration characteristics of laminated sandwich plates subjected to in-plane forces is studied taking imperfections at the layer interfaces. The plate problem, which is unattended so far, is modeled by a refined plate theory where the transverse shear stress has parabolic through thickness variation with continuity at the layer interfaces and it becomes zero at the plate top and bottom surfaces. The interfacial imperfection is represented by a linear spring layer model. Based on these a new triangular element is developed where proper attention has been paid on the inter-elemental continuity requirement posed by the plate theory.
Synthesis of Room Responses Using the Virtual Source Representation and the Comb-Nested Allpass Filters
Authors: Bai Mingsian R. , Ou Kwuen-Yieng
Published: April 2007

An artificial reverberator is proposed in this paper to synthesize room responses. The method employs the virtual source representation and the comb-nested allpass filters to generate the early reflection and late reverberation, respectively, of room responses. The virtual source method is based on a simple representation of sound field with a distribution of discrete simple sources on the boundary. The complex strengths of the virtual sources are then calculated by solving a frequency domain least-square problem. Parameters such as room geometry, size, and wall absorption are naturally incorporated into the synthesis process. The filtering property of human hearing is also exploited in a nonuniform sampling procedure to further simplify the computation. Apart from the early reflection, a comb-allpass filter network is adopted to simulate late reverberations. Optimal parameters of the comb-allpass filter network are obtained using the genetic algorithm (GA). The energy decay curve (EDC) is chosen as the objective function in the GA procedure. Numerical simulations are carried out for a rectangular room and a concert hall model to verify the proposed technique. Subjective listening experiments demonstrate that the present technique is capable of conferring remarkable realism of room responses.
SCF
Fbxl3
Controls the Oscillation of the Circadian Clock by Directing the Degradation of Cryptochrome Proteins
Authors: Busino Luca , Bassermann Florian , Maiolica Alessio , Lee Choogon , Nolan Patrick M. , Godinho Sofia I. H. , Draetta Giulio F. , Pagano Michele
Published: April 2007

One component of the circadian clock in mammals is the Clock-Bmal1 heterodimeric transcription factor. Among its downstream targets, two genes,
Cry1
and
Cry2
, encode inhibitors of the Clock-Bmal1 complex that establish a negative-feedback loop. We found that both Cry1 and Cry2 proteins are ubiquitinated and degraded via the SCF
Fbxl3
ubiquitin ligase complex. This regulation by SCF
Fbxl3
is a prerequisite for the efficient and timely reactivation of Clock-Bmal1 and the consequent expression of
Per1
and
Per2
, two regulators of the circadian clock that display tumor suppressor activity. Silencing of Fbxl3 produced no effect in
Cry1
–/–
;
Cry2
–/–
cells, which shows that Fbxl3 controls clock oscillations by mediating the degradation of CRY proteins.