bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of heterogeneous near‐surface materials by joint 2D inversion of dc resistivity and seismic data
Authors: Gallardo Luis A. , Meju Max A.
Published: July 2003

We have developed a robust 2D joint inversion scheme incorporating the new concept of cross‐gradients of electrical resistivity and seismic velocity as constraints so as to investigate more precisely the resistivity‐velocity relationships in complex near‐surface environments. The results of joint inversion of dc resistivity and seismic traveltime data from collocated experiments suggest that one can distinguish between different types or facies of unconsolidated and consolidated materials, refining a previously proposed resistivity‐velocity interrelationship derived from separate inversions of the respective data sets. A consistent interpretive structural model can be obtained from the joint inversion models.
Hydrographic survey in the dying Aral Sea
Authors: Zavialov P. O. , Kostianoy A. G. , Emelianov S. V. , Ni A. A. , Ishniyazov D. , Khan V. M. , Kudyshkin T. V.
Published: July 2003

We report the results of a hydrographic survey conducted in November, 2002, in the Uzbekistan part of the western basin of the dying Aral Sea. There were very few hydrographic measurements in this region since at least early 1990s. The salinity in the western deep basin of the Aral Sea varied from about 82 psu at the surface to over 94 psu at the bottom. The absolute lake surface level was about 30.5 m. Hence, the observed salinity values were much higher, and the level much lower, than expected according to earlier predictions. The density in the western basin exhibited an extremely strong stratification of ∼11 kg/m3 per ∼20 m in the bottom layer. The picnocline was accompanied by a temperature inversion whose magnitude was ∼4°C. The observed density stratification effectively isolating the lower part of the water column from surface exchanges may be responsible for the increase of summer SSTs and evaporation rates reported in previous studies. We discovered the hydrogen sulphide contamination in the bottom layer whose upper limit was at the depth of approximately 22 m. Estimates suggest that the western basin salinization occurs not only because of the local evaporation, but also because of the assimilation of the saltier eastern basin water in the course of the interbasin exchange through the connecting channel. The satellite imagery analysis, in particular the Maximum Cross‐Correlation method, suggests that the circulation pattern in the Aral Sea in its present limits is cyclonic under the eastern winds that are predominant in the region throughout the year.
Coseismic slip distribution of the 2002 MW7.9 Denali fault earthquake, Alaska, determined from GPS measurements
Authors: Hreinsdóttir Sigrún , Freymueller Jeffrey T. , Fletcher Hilary J. , Larsen Christopher F. , Bürgmann Roland
Published: July 2003

On 3 November 2002 an MW7.9 earthquake occurred in central Alaska. The earthquake ruptured portions of the Susitna Glacier, Denali, and Totschunda faults. Inversion of the GPS‐measured displacement field indicates that the event was dominated by a complex, right‐lateral strike‐slip rupture along the Denali fault. GPS sites closest to the epicenter show the effect of thrust motion on the Susitna Glacier fault. The preferred coseismic slip model, with MW7.8, indicates relatively low slip on the western part of the rupture and high slip from about 60 km east of the hypocenter extending to the junction of the Denali and Totschunda faults. We find mostly shallow slip from the surface to 15 km depth, but the inversion suggests one large deep slip patch about 110 km east of the hypocenter. Our model predicts surface slip in good agreement with surface geological observations, where model resolution is good.
Bimodal size distribution of C2–C4 dicarboxylic acids in the marine aerosols
Authors: Mochida Michihiro , Umemoto Nobuhiko , Kawamura Kimitaka , Uematsu Mitsuo
Published: July 2003

Size distributions of C2–C4 dicarboxylic acids in aerosols were studied in the marine boundary layer (MBL) of the central to western North Pacific as well as off the coasts of East Asia. C2–C4 Diacids were mostly present in submicron particles over the coastal ocean, but they were relatively abundant in supermicron particles over the remote ocean. We found that the peak diameters for the concentration of C2–C4 diacids in supermicron particles over the remote ocean were similar to that for the surface‐area distribution of sea salts, suggesting a deposition of gaseous diacids on sea‐salt particles and/or their heterogeneous formation during long‐range transport. The present results, together with the solubility product of calcium oxalate, suggest that oxalic acid in sea salts may partly form insoluble calcium salt, which potentially enhances the uptake of gaseous oxalic acid by the aerosol particles.
Neural networks for automated classification of ionospheric irregularities in HF radar backscattered signals
Authors: Wing S. , Greenwald R. A. , Meng C.‐I. , Sigillito V. G. , Hutton L. V.
Published: July 2003

The classification of high frequency (HF) radar backscattered signals from the ionospheric irregularities (clutters) into those suitable, or not, for further analysis, is a time‐consuming task even by experts in the field. We tested several different feedforward neural networks on this task, investigating the effects of network type (single layer versus multilayer) and number of hidden nodes upon performance. As expected, the multilayer feedforward networks (MLFNs) outperformed the single‐layer networks. The MLFNs achieved performance levels of 100% correct on the training set and up to 98% correct on the testing set. Comparable figures for the single‐layer networks were 94.5% and 92%, respectively. When measures of sensitivity, specificity, and proportion of variance accounted for by the model are considered, the superiority of the MLFNs over the single‐layer networks is much more striking. Our results suggest that such neural networks could aid many HF radar operations such as frequency search, space weather, etc.
Incidence and predictors of self‐reported tooth loss in a representative sample of Norwegian adults
Authors: Haugejorden Ola , Klock Kristin S. , Trovik Tordis A.
Published: July 2003

Abstract  

Objectives: The purpose of this study was to determine the self‐reported 12‐month incidence of tooth loss among Norwegian adults and to assess the association between tooth loss and some predictor variables.

Methods: Of a two‐stage nation‐wide, representative random sample (n = 3958), information was obtained from 2682 subjects aged 20–79 years and the response rate was 68%. Telephone or face‐to‐face interviews by interviewers employed by the Central Bureau of Statistics (CBS) of Norway. Information was collected about demographic characteristics, the number of natural teeth present, the number of teeth lost during the last 12 months, and belief in keeping natural teeth for life. The present analyses are based on 2520 persons 20–79 years of age.

Results: The proportion of respondents who reported losing one or more teeth was 6.45% (95% confidence limits (CL) = 5.49, 7.41). The participants who reported extractions had lost on average 1.54 (range 1–9) teeth. Multiple logistic regression analysis revealed a borderline significant effect of the level of education (OR = 0.68, 95% CL = 0.46, 1.00), i.e. the odds of losing one or more teeth during the last 12 months were lower among persons with more than 12 years of education than among persons with less education. The explained variance was 1.9%.

Conclusion: The annual incidence rate of tooth loss among Norwegian adults was found to lie within the range reported from other industrialized countries. After controlling for socio‐demographic variables and the number of teeth present, the only borderline significant predictor of the incidence of tooth loss was the level of education.
Evaluation of a dental care program for school beginners in a Paris suburb
Authors: Azogui‐Lévy S. , Lombrail P. , Riordan P. J. , Brodin M. , Baillon‐Javon E. , Pirlet M. C. , Boy‐Lefèvre M. L.
Published: July 2003

Abstract  

Objectives: Dental care for children is available in France, but the method of administration is cumbersome: care is generally provided by private dentists, and parents can claim reimbursement of at least 70% of the costs afterwards. In the Département of Val d'Oise (north of Paris and including some densely populated suburbs), a scheme is in place to provide 100% reimbursement. To encourage participation, schoolchildren are screened by dentists who advise if treatment is needed. The objective of this study was to ascertain the effectiveness of screening as a stimulus for seeking dental care.

Methods: In two towns, 6–7‐year‐old schoolchildren were cluster‐sampled to give 507 participants. At screening, about half of the participants were found to be in need of operative treatment. Questionnaires about demographic and other background factors were sent home. From those needing treatment, 186 (77%) sets of questionnaires were returned. These persons were the analytical basis of the study. Six months after screening, the 186 participants were examined to estimate whether they had sought and received treatment as advised.

Results: The majority of the participants came from low socioeconomic and deprived backgrounds. Most of the parents were born in countries outside Europe. Only about one‐quarter of the children advised to seek treatment had actually done so after 6 months. Slightly under half of those who were treated had claimed the reimbursable amount after the treatment. Of the 186 participants needing treatment, 24% had more than 4 dt + DT but 70% of these had not received any care.

Conclusion: These findings suggest that even when costs are totally reimbursed, most children in need of care do not receive it; the greater the need of care, the lower the likelihood of getting it. The deprived people and immigrants frequently inhabiting the Parisian suburbs seem to experience cultural, financial, linguistic, and administrative barriers to care, which impede uptake and which must be changed if these children are to enjoy improved dental health.
Perceived oral health: changes over 5 years in one Swedish age‐cohort
Authors: Ståhlnacke Katri , Söderfeldt Björn , Unell Lennart , Halling Arne , Axtelius Björn
Published: July 2003

Abstract  

Objectives: The purpose of this study was to investigate if a change in the social gradients in perceived oral health occurred over a 5‐year period, 1992–97, using a cohort population from two Swedish counties.

Methods: In 1992, a cross‐sectional mail questionnaire was sent to all 50‐year‐old persons in two counties in Sweden, Örebro and Östergötland, and altogether there were 8888 persons. In 1997, the same population was sent a new questionnaire. The cohort, comprising the same respondents from 1992 and 1997, was of 5363 persons. An index of perceived oral health was constructed out of three questionnaire variables: satisfaction with teeth, chewing ability and the number of remaining teeth. This index value was set as a dependent variable in a regression model. Reports of toothache were investigated in a separate logistic regression model.

Results: There were obvious social gradients in the perceived oral health index both in 1992 and in 1997. Marital status, foreign birth, education and occupation were all substantially related to the perceived oral health. The change in perceived oral health was analyzed. Almost half of the cohort (47.4%) showed no change at all. Those with increased and those with decreased health were rather evenly distributed on both sides, with 22.0% with better health in 1997 and 30.6% with worse health. Gender and education were related to toothache experience.

Conclusion: Changes have been moderate in the perceived oral health in this cohort, despite the rather drastic changes in the remuneration of dental care during this study time. On the other hand, this also means that the social differences remain, despite the official goals of increased equity.
Observer agreement in the grading of oral epithelial dysplasia
Authors: D. J Brothwell , D. W Lewis , G Bradley , I Leong , R. C. K Jordan , D Mock , J. L Leake
Published: July 2003

Abstract  

Objectives: To determine the extent of observer agreement in diagnosis of oral epithelial dysplasia (OED). Published studies of OED examiner agreement report relatively low agreement levels; however, these studies were limited by the methodologies employed. Methods: For this study, 64 slides were each independently examined twice by three oral pathologists. Consistency was assessed by determining intra‐ and interexaminer agreement. Conformity was assessed by using the modal diagnosis as a gold standard. Results: The group showed moderate interobserver agreement when grading the presence or absence of OED with a group‐simple kappa (Ks) of 0.51 (95% CI = 0.42–0.61), and substantial agreement when using a 5‐point ordinal scale with a group‐weighted kappa (Kw) of 0.74 (95% CI = 0.64–0.85). The group showed fair to substantial intraexaminer agreement when assessing the presence or absence of OED, with Ks ranging from 0.22 to 0.78, and showing almost a perfect agreement using a 5‐point ordinal scale, with Kw ranging from 0.82–0.96. Conformity with the comparison standard modal diagnosis was almost perfect, with pairwise Kw ranging from 0.81 to 0.92. Conclusion: Overall, there was substantial intra‐ and interobserver consistency and almost perfect conformity in the grading of OED. Appropriate statistical methods are necessary to determine the degree of observer agreement.
Effects of glass ionomer sealants in newly erupted first molars after 5 years: a pilot study
Authors: Taifour Dia , Frencken Jo E. , Van′t Hof Martin A. , Beiruti Nabil , Truin Gert‐Jan
Published: July 2003

Abstract – Objectives: The aim of the study was to investigate the caries‐preventive effect of high‐filled glass ionomer sealant in newly erupted first molars in a high‐risk group. This investigation is part of a larger study amongst eight hundred and thirty‐five 6–7‐year‐old Syrian children.

Methods: Children that had 1, 2 or 3 just erupted or erupting and at least one unerupted first molar (control) were enrolled in this pilot study. A total of 60 children fulfilled the inclusion criteria. There were 49 children with a total of 83 sealants available for examination at the evaluation year 5.

Results: Almost two out of the three sealants (69%) had disappeared between evaluation years 2 and 3. 1.2% (SE = 1.2) of the sealants survived were fully retained and 10.3% (SE = 3.3) of the sealants survived were fully and partially retained at the evaluation year 5. Caries prevalence of the children in the study group at the evaluation year 5 was 55%. The Odds ratio concerning sealed and control group at year 5 was 2.6 with 95% confidence limits of 1.2 and 5.7, implying a relative risk (RR) of 2.1. Unsealed unerupted first molars had 2.1 times higher chance than sealed newly erupted first molars to develop dentinal lesions in this child population after 5 years.

Conclusions: It is concluded that sealing newly erupted first molars with high‐filled glass ionomer may be a caries‐preventive measure in high‐risk children. However, a well‐designed clinical trial should be implemented to confirm the initial findings.
Changes in restorative caries treatment in 15‐year‐olds in Oslo, Norway, 1979–1996
Authors: Gimmestad Anne Løvberg , Holst Dorthe , Fylkesnes Knut
Published: July 2003

Abstract  

Objectives: To examine changing patterns regarding restorative treatment criteria for dental caries.

Methods: A representative sample (n = 215) was drawn from all 15‐year‐olds receiving dental treatment in the Public Dental Service (PDS) in Oslo, Norway for each of the years 1979, 1989, 1993 and 1996. Information from clinical records and bitewing radiographs on caries treatment was collected. The results presented in this paper pertain to 198, 201, 209 and 208 subjects in each group.

Results: The results revealed dramatic changes in the use of restorative treatment criteria. Only 16% of tooth surfaces were treated in 1996 according to the criteria from 1979. The number of sound surfaces was found to have increased by 39% whereas the number of filled surfaces was reduced by 92%. In spite of more stringent criteria for restorative treatment, the number of D4 lesions did not increase.

Conclusion: The practice of change in restorative treatment continued during the 17 years of study. Though the number of decayed surfaces appeared to be stable during the period, in reality, there was a reduction in caries occurrence during the first 10‐year period (1979–1989). A conceptual model of dentists' caries‐related treatment decisions outlined by Bader & Shugars may be used to explain parts of the rapid change in the criteria used in the PDS in Oslo.
Application of survival analysis to carious lesion transitions in intervention trials
Authors: Baelum Vibeke , Machiulskiene Vita , Nyvad Bente , Richards Alan , Væth Michael
Published: July 2003

Abstract  

Objective: To demonstrate the usefulness of a survival‐time regression model for the analysis of data from two 3‐year trials of the caries‐preventive effect of sugar‐substituted chewing gums and fluoride toothpaste, carried out among 892 Lithuanian children.

Methods: A caries onset was defined as a transition from sound to carious and a caries recovery was defined as a transition from carious to sound. The time at risk for each type of transition was calculated. Using an exponential survival‐time regression model, the hazard ratios for the covariates experimental group (control, sugar substitute, fluoride), age, gender, surface type and posteruptive surface age was estimated. This analysis was repeated using two alternative definitions of the caries transitions.

Results: The analyses confirmed that caries rates are higher in occlusal surfaces, and that posteruptive surface age influences caries rates. Moreover, it also confirmed that fluoride affects the outcome of ongoing caries activity more than the initiation of caries.

Conclusions: Survival‐time analysis of caries transitions allows for the extraction of much more information from caries trials than does the traditional DMF‐based analysis, and traditional DMF incremental values may easily be derived from the models.
Cigarette smoking, snuff use and alcohol drinking: coexisting risk behaviours for oral health in young males
Authors: Wickholm Seppo , Galanti M. Rosaria , Söder Birgitta , Gilljam Hans
Published: July 2003

Abstract  

Objectives: The use of oral moist snuff (snus) is widespread among Swedish men, but little is known about the use in adolescents. The aim of this study was to describe patterns of snuff dipping, smoking and alcohol drinking in a sample (n = 6287) of 9th grade male students participating in a census survey in the Stockholm region.

Results: About 20% of the sample reported use of snus, and more than two‐thirds of snus users were also cigarette smokers. Among current nonusers of tobacco (66% of the sample), 14% reported frequent binge drinking, in contrast to 49% among current exclusive cigarette smokers, 60% among exclusive snus users and 69% among users of both cigarettes and snus. The estimated mean annual consumption of alcohol was 5–10 times higher among tobacco users than among nonusers, with users of snus consuming more alcohol than smokers. Compared to non‐ or minimal drinkers, heavy alcohol drinkers had a disproportionately higher risk to report snus use, after adjustment for smoking behaviour (OR = 16.7, 95% CI 12.9–21.7). When the analysis was restricted to users of only one type of tobacco, heavy drinkers were twice as likely to report snus, rather than cigarette, use.

Conclusions: Both tobacco use and alcohol drinking have been independently associated with a variety of pathological oral conditions in adults. These behaviours coexist in early adolescence. Their effect on oral health need to be investigated in prospective studies and should be of concern to the dental professionals.
Effect of fluoridated milk on caries in primary teeth: 21‐month results
Authors: Bian Jin Y. , Wang Wen H. , Wang Wei J. , Rong Wen S. , Lo Edward C. M.
Published: July 2003

Abstract  

Objectives: Use of fluoridated milk has been shown to be a safe and effective method to prevent caries in permanent teeth in children. However, studies on its effectiveness on caries prevention in the primary teeth are scarce. The purpose of the present study was to evaluate the effect of milk fluoridation on caries development in young Chinese children.

Methods: This was a community‐based demonstration study carried out in Beijing, China. All children in three selected kindergartens were invited to participate. Each participant consumed 200 ml of fluoridated milk (concentration 2.5 mg F− per litre) per day from Monday to Friday in the kindergarten, and was given two packs of fluoridated milk (250 ml) for consumption at home on Saturday and Sunday every week. Children from a similar background, but without access to fluoridated milk, attending two other kindergartens, were used as the control.

Results: There were 534 children (mean age 54 ± 4 months) and 305 children (mean age 53 ± 4 months) in the test and control groups, respectively, at baseline. After 21 months, 417 and 247 children in the test and control groups, respectively, remained in the study. There was no statistically significant difference in the baseline mean dmft scores between the two groups (3.2 vs. 3.5, P = 0.312). After 21 months, the mean net caries increment was 0.4 dmft for the test group and 1.3 dmft for the control group (t‐test, P < 0.001).

Conclusion: The consumption of fluoridated milk by the kindergarten children in Beijing was an effective measure in preventing caries in the primary teeth.
Validation of an oral health quality of life index (GOHAI) in France
Authors: Tubert‐Jeannin S. , Riordan P. J. , Morel‐Papernot A. , Porcheray S. , Saby‐Collet S.
Published: July 2003

Abstract Oral health has traditionally been defined in terms of disease. Today, health is seen in a wider context: taking into account its impact on everyday living. Several indices attempt to capture this dimension. The Geriatric Oral Health Assessment Index (GOHAI) has been adapted for general use and tested on adult samples, mainly in North America. Language, cultural norms and the health care system in France are different and this raises the need to validate the GOHAI in France before it receives widespread use.

Objectives: The purpose of this study was to test the validity of a French version of the GOHAI.

Methods: The GOHAI is based on responses to a 12‐item self‐administered questionnaire. The items were translated into French, back‐translated and compared with the original. After pilot testing and minor modifications, the French version was administered to a group of low‐income persons benefiting from the national health insurance system (n = 260, 18–45 years). Measures for stability and internal consistency were calculated. Concurrent and discriminant validity were assessed.

Results: Cronbach's α (0.86) showed a high internal consistency and homogeneity between items. Item‐scale correlations varied between 0.40 and 0.78. Repeat administration of the GOHAI to 32 participants gave weighted kappa coefficients from 0.51 to 0.87 and a Pearson's correlation coefficient of 0.87. Low GOHAI scores were associated with perceptions of poor oral and general health, low satisfaction with oral health and a perceived need for dental care. There were significant relationships between the GOHAI score and most objective measures of dental status except FT. Younger, well‐educated and higher income respondents were more likely to have a high GOHAI score.

Conclusion: The French version of the GOHAI exhibits satisfactory psychometric properties but two items (one about swallowing, the other with complex sentence structure) had poor stability.
The relationship between traumatic dental injuries and adolescents' development along the life course
Authors: Nicolau Belinda , Marcenes Wagner , Sheiham Aubrey
Published: July 2003

AbstractFew models have been proposed to explain the aetiology of traumatic dental injuries. Those that have, focus on risk factors at present stage of life. The contribution of risk factors for dental injuries at different stages of life needs to be investigated.

Objectives: To test the relationship between life course experiences and the occurrence of traumatic dental injuries in adolescents.

Methods: A cross‐sectional survey was used to collect data retrospectively. Out of a total number of 764 eligible 13‐year‐old‐adolescents enrolled in private and public schools located in urban areas in the town of Cianorte, Brazil, 652 (85%) agreed to participate in the study. They were interviewed and examined for traumatic dental injuries by two trained dental epidemiologists using validated criteria. The interviews collected information on socioeconomic circumstances, family related variables, school grade and anthropometric measures (height and weight).

Results: Adolescent boys, those from non‐nuclear families, those reporting high levels of paternal punishment and those who were at lower grades at school for their age were more likely to experience dental injuries than girls, adolescents from nuclear families, those reporting low levels of paternal punishment and those who were at higher grades at school.

Conclusion: It was concluded that adolescents who experienced adverse psychosocial environments along the life course had more traumatic dental injuries than their counterparts who experienced more favourable environments.
Students' perceptions of the acceptability of behaviour management techniques
Authors: Newton J. Timothy , Sturmey Peter
Published: July 2003

The aim of the present study was to determine the perceptions of dental students of the acceptability of different forms of behaviour management for children. The effect of client characteristics (typically developing or learning disabled), intervention method (relaxation training and reinforcement or physical restraint) and treatment outcome (good or poor) on acceptability ratings made by fourth year dental students was determined. Students rated the acceptability of treatments on the basis of written vignettes using a standardized measure of the acceptability of behavioural treatments (the Treatment Evaluation Inventory, TEI, Kazdin, French and Sherick 1981). The study had a full factorial design; all possible combinations of variables were represented in the vignettes. The results were analysed using ANOVA models. There were significant main effects of intervention method and treatment outcome, indicating that less restrictive methods and good intervention outcome were rated as more acceptable. Significant two‐ and three‐way interactions were found, which suggested that the use of restrictive methods may be perceived as more acceptable for a child with learning disabilities even when the outcome was poor. The second order interactions revealed that the acceptability of restrictive techniques was improved less markedly by a good outcome. This study highlights the importance of empirically evaluating outcome and treatment restrictiveness when engaging in behaviour management during dental procedures.
Attendance at and self‐perceived need for continuing education among Mongolian dentists
Authors: Tseveenjav Battsetseg , Vehkalahti Miira M. , Murtomaa Heikki
Published: July 2003

In May 2000, a questionnaire‐based survey was targeted at all Mongolian dentists practising in the capital city of Mongolia in May 2000 with the aim of evaluating attendance at and the self‐perceived need for continuing education (CE) in relation to their background characteristics and to their attitude towards CE. The response rate was 98% (n = 245), with 38% of the dentists reporting a CE learning opportunity in at least one of the clinical disciplines of dentistry during the 2 years prior to the survey. A need for CE in at least one of the disciplines was perceived by 58%. A dentist's field of practice and attitude towards CE were the significant factors for attendance, whereas length of working experience, field of practice, holding a postgraduate degree, and having attended CE courses were significant factors for perceiving a need for CE, when controlling for all other variables in the logistic regression analyses (P < 0.05). There seems to be a need for an increased attendance at CE courses among the dentists and a need for preparing them to have a positive attitude towards CE. On the other hand, creating an organized CE system which produces courses for dental practitioners, based on their need, will be at present a challenge for the Mongolian dental profession.
Dental undergraduate expectations and opinions of Web‐based courseware to supplement traditional teaching methods
Authors: Eynon R. , Perryer G. , Walmsley A. D.
Published: July 2003

The rapid growth of Internet for the delivery of information has enabled teaching materials to be placed on websites allowing student access to course material. It is the aim of this paper to evaluate a cohort of dental undergraduate students who have used Web‐based courseware in prosthetic dentistry for a semester. A questionnaire was distributed to clinical undergraduate students prior to the use of the prosthetics course to determine their experience of using the World Wide Web (WWW) and their expectations of an online course. A second questionnaire was distributed at the end of 6 months which asked about their usage and opinions of the prosthetics Web‐based courseware. The main concerns raised at the beginning of the course were related to computer access, the ability to use computers, the time involved and their conception that the e‐course would be an additional burden. The main potential benefits were perceived to be convenience, availability of information and the ability to reinforce or catch up on aspects of the module they did not understand or had missed. Feedback at the end of the year showed that most students had accessed the Web‐based courseware site at least once a month and, generally, their comments were favourable, dispelling some of the initial perceived fears. They felt that the website was a quick and convenient way to access information and was a good additional resource. Access to the site and printing information were the main problems raised by the students who had to use a shared cluster. In conclusion, Web‐based courseware was felt to be a useful additional resource for students. However, this research showed that sufficient computers and printers must be available for such a resource to become an integrated part of the dental course.
Teaching oral surgery to undergraduate students: a pilot study using a Web‐based practical course
Authors: Corrêa Luciana , De Campos Antonio Carlos , Souza Suzana C. O. M. , Novelli Moacyr Domingos
Published: July 2003

The Internet has been used in oral surgery teaching mainly to deliver learning material across the World Wide Web and to make use of online interactivity resources in everyday surgical practice, such as by e‐mails, discussion groups, and chats. The aim of this paper is to describe and evaluate a Web‐based practical course on oral surgery principles, which was applied to undergraduate students. This course was investigated as a distance learning simulation in which the student would be performing surgical activities at home, and the teacher and the school environment would be absent. A Web site was created containing the course material. For this study, the students participated in the Web‐based course in a multimedia lab equipped with computers and Internet, internal sound system and TV circuits. In the event of significant mistakes by students, the TV circuit could be used to show the correct procedure for all the participants at the same time. Microcameras were used to monitor the student's actions during the Internet use. Students' impressions were determined by a questionnaire. Computer manipulation with ease and antiergonomic postures were observed. We concluded that distance learning courses with practical modules must be considered as a special type of educational modality, with reference to the relationship between the student and the computer.
A preliminary study to investigate the potential of plasma screen technology in small group teaching for dental undergraduates
Authors: Packer Mark E. , Coward Trevor J. , Wakeley Roderick , Fenlon Michael R.
Published: July 2003

Aim:  This preliminary study was devised to ascertain whether students considered that they had an adequate view of demonstrated procedures, while observing these directly at the workbench, or indirectly on a remote plasma screen. In addition, this study sought to identify whether the students observing remotely believed that they had been disadvantaged by the inability to question the demonstrator during the demonstration.

Methods:  Seventeen students divided into two groups observed a live demonstration of a laboratory technical procedure either at the workbench, or remotely at a plasma screen with the aid of video cameras. They subsequently observed a second demonstration with the roles reversed. Questionnaires were used to obtain the students' views of their ability to see and interact with the demonstrator.

Results:  The responses of the students observing the demonstration at the plasma screen indicated that (they felt that) they were able to see the demonstration more clearly than those observing at the workbench. Those observing at the plasma screen first, in particular indicated this. The majority of students acknowledged their inability to ask questions while observing at the plasma screen. There was overwhelming support for the idea that the plasma screen should be used to complement the demonstration at the workbench.

Conclusion:  Plasma screen technology has considerable potential as a teaching tool for small groups of students, where it can afford significantly superior views of practical procedures. The students considered that the plasma screen would be best employed to provide close‐up views to supplement a live demonstration. When used remotely, the apparatus may be used more satisfactorily if videoconferencing technology is also employed to facilitate interaction with the demonstrator.
The use of PBL to facilitate the development of professional attributes in second year dental students
Authors: Pau A. K. H. , Croucher R.
Published: July 2003

Objectives:  To investigate dental students' perception as to whether PBL can facilitate the development of professional attributes.

Design:  A cross‐sectional survey of second year dental undergraduates in a UK dental school.

Method:  At the end of a PBL module, all students were asked to complete a fully structured questionnaire. Data were collected on socio‐demographics, aspects of the PBL experience and the extent to which students perceived that PBL had facilitated the development of professional attributes.

Results:  The response rate was 96%. The frequency distributions of the PBL experience and development of professional attributes were skewed to the positive. Non‐white students, compared to white students, rated significantly more highly the extent to which they thought PBL had facilitated the development of professional attributes. Differences between male and female students, and mature and less mature students were not significant. Students who rated the PBL experience positively were significantly more likely to rate highly the extent to which they thought PBL had facilitated the development of professional attributes.

Conclusions:  The factors that affect the relationship between ethnicity and development of professional attributes need further research. To enhance the development of professional attributes, teachers of PBL need to ensure that students find the learning experience worthwhile and stimulating.
Use of Web‐based formative assessment to support student learning in a metabolism/nutrition unit
Authors: Henly Debra C.
Published: July 2003

In 2002, an integrated basic science course was introduced into the Bachelor of Dental Sciences programme at the University of Queensland, Australia. Learning activities for the Metabolism and Nutrition unit within this integrated course included lectures, problem‐based learning tutorials, computer‐based self‐directed learning exercises and practicals. To support student learning and assist students to develop the skills necessary to become lifelong learners, an extensive bank of formative assessment questions was set up using the commercially available package, WebCT®. Questions included short‐answer, multiple‐choice and extended matching questions. As significant staff time was involved in setting up the question database, the extent to which students used the formative assessment and their perceptions of its usefulness to their learning were evaluated to determine whether formative assessment should be extended to other units within the course. More than 90% of the class completed formative assessment tasks associated with learning activities scheduled in the first two weeks of the block, but this declined to less than 50% by the fourth and final week of the block. Patterns of usage of the formative assessment were also compared in students who scored in the top 10% for all assessment for the semester with those who scored in the lowest 10%. High‐performing students accessed the Web‐based formative assessment about twice as often as those who scored in the lowest band. However, marks for the formative assessment tests did not differ significantly between the two groups. In a questionnaire that was administered at the completion of the block, students rated the formative assessment highly, with 80% regarding it as being helpful for their learning. In conclusion, although substantial staff time was required to set up the question database, this appeared to be justified by the positive responses of the students.
C and N mineralisation in the decomposer food webs of a European forest transect
Authors: Schröter Dagmar , Wolters Volkmar , De Ruiter Peter C.
Published: July 2003

Belowground processes are essential for the overall carbon and nitrogen fluxes in forests. Neither the functioning of the soil food web mediating these fluxes, nor its modulation by environmental factors is sufficiently understood. In this study the belowground carbon and nitrogen mineralisation of four European coniferous forest sites (northern Sweden to north‐east France) with different climate and N depositional inputs was analysed by investigating the soil food webs using field observations and modelling. The soil fauna directly contributed 7–13% to C mineralisation, among which the testate amoebae (Protozoa) made the largest contribution. Microbial grazing was suggested to have an important indirect effect by stimulating bacterial turnover. Due to relatively high C:N ratios of their substrate, bacteria immobilized N, while the fauna i.e. testate amoebae, nematodes, microarthropods and enchytraeids, counteracted this N immobilisation.

Despite similar food web biomass, the sites differed with respect to food web structure and C and N flows. Model calculations suggested a significant influence of food web structure on soil ecosystem processes in addition to environmental factors and resource quality. Mineralisation rates were lowest at the low N input boreal site with a food web dominated by fungal pathways. Further south, as N availability increased, bacterial pathways became more important and the cycling of C and N was faster. The bioavailability of degradable C sources is suggested to be a limiting factor for microbial activity and overall mineralisation rates. In this respect, above‐ and belowground interactions e.g. transfers of labile C sources from the vegetation to the decomposer system deserve further attention.

Our study revealed the combined effects of climate and nutrient inputs to ecosystems and the subsequent changes in the structure and functioning of the systems. If decomposition, and therefore carbon loss, is stimulated as a consequence of structural and/or nutritional changes, resulting for example from continuous industrial N emission, the storage capacity of forest ecosystems could be altered.
Testing the defence trade‐off hypothesis: how contents of nutrients and secondary compounds affect fruit removal
Authors: Schaefer H. Martin , Schmidt V. , Winkler H.
Published: July 2003

Fruit removal has been attributed to the contents of nutrients and secondary compounds. We tested two alternative models of the chemical defence of fruits for the contents of nutrients, phenols, and condensed tannins and the nutrient content pypothesis stating that nutrient rich fruits are preferably removed. The defence trade‐off hypothesis assumes that the retention of deterrent secondary metabolites in ripe fruits reflects a trade‐off between defence against pests and attraction of dispersers. The removal‐rate model of this hypothesis predicts a negative relationship of nutrients and levels of secondary compounds due to short persistence and thus low infection risk of fruits. The nutrient‐toxin titration model postulates a positive relationship assuming that profitable fruits are able to afford high levels of protection due to a compensatory effect of high nutrient levels for consumers. Fruit removal by the entire frugivorous community for 33 plant species was best described by a dose–response curve, mediated by the stimulating effects of lipid, carbohydrate, and nitrogen contents, while the contents of phenols and water deterred removal. Moreover, traits that stimulated removal prevailed in ripe fruits except for nitrogen, unripe fruits had higher contents of phenols and nitrogen. Profitable fruits were quickly removed and had low phenolic contents. Thus, fruit removal was characterised by the nutrient content hypothesis and pulp contents by the removal‐rate model. The selective pressure of 84 frugivorous species integrated into an unidirectional preferential removal of nutrient rich fruits. The consistency of consumers’ preferences implies the potential for habitat shaping processes due to differential recruitment of plant species based on dispersers’ choices.
Density dependence, regulation and open‐closed populations: insights from the wigeon,Anas penelope
Authors: Pöysä Hannu , Pesonen Mauri
Published: July 2003

We investigated whether the degree of exchange with other populations affects the occurrence of density‐dependent regulation. We contrasted data from an Icelandic and a Finnish population of breeding wigeons (Anas penelope), the former population being more closed than the later. We looked for density dependence in time‐series data and investigated whether breeding success is density dependent and plays a role in population dynamics and regulation. Time‐series analysis did not reveal density‐dependent regulation in either population. Nor did we find evidence of density‐dependent breeding success in either population. However, population growth rate appeared to be strongly dependent on the breeding success in the previous year in the closed population but not in the open population. Our findings underline how important it is to link time‐series analysis to the study of potential stabilizing mechanisms in order to understand population dynamics and regulation. We also suggest that it may be a difficult task to achieve sustainability in waterfowl harvesting, the theoretical basis of which is density‐dependent population regulation.
Variation in trophic shift for stable isotope ratios of carbon, nitrogen, and sulfur
Authors: McCutchan James H. , Lewis William M. , Kendall Carol , McGrath Claire C.
Published: July 2003

Use of stable isotope ratios to trace pathways of organic matter among consumers requires knowledge of the isotopic shift between diet and consumer. Variation in trophic shift among consumers can be substantial. For data from the published literature and supplementary original data (excluding fluid‐feeding consumers), the mean isotopic shift for C was +0.5±0.13‰ rather than 0.0‰, as commonly assumed. The shift for C was higher for consumers analyzed as muscle (+1.3±0.30‰) than for consumers analyzed whole (+0.3±0.14‰). Among consumers analyzed whole, the trophic shift for C was lower for consumers acidified prior to analysis (−0.2±0.21‰) than for unacidified samples (+0.5±0.17‰). For N, trophic shift was lower for consumers raised on invertebrate diets (+1.4±0.21‰) than for consumers raised on other high‐protein diets (+3.3±0.26‰) and was intermediate for consumers raised on plant and algal diets (+2.2±0.30‰). The trophic shift for S differed between high‐protein (+2.0±0.65‰) and low‐protein diets (‐0.5±0.56‰). Thus, methods of analysis and dietary differences can affect trophic shift for consumers; the utility of stable isotope methods can be improved if this information is incorporated into studies of trophic relationships. Although few studies of stable isotope ratios have considered variation in the trophic shift, such variation is important because small errors in estimates of trophic shift can result in large errors in estimates of the contribution of sources to consumers or in estimates of trophic position.
Seasonal and ontogenetic dynamics in trophic transmission of parasites
Authors: Amundsen Per‐Arne , Knudsen Rune , Kuris Armand M. , Kristoffersen Roar
Published: July 2003

Transmission rates from the intermediate (amphipods) to the definitive hosts (fish) were quantified for two helminth species (Cyathocephalus truncatus, Cestoda, and Cystidicola farionis, Nematoda) both seasonally and through the ontogeny of the final hosts (arctic charr, Salvelinus alpinus, and brown trout, Salmo trutta). Amphipods (Gammarus lacustris) were important prey for both fish species, especially in the autumn. Both parasite species had low infection levels in amphipods compared to high abundance in fish. The seasonal variations in transmission rate of C. truncatus procercoids from amphipods to fish were in accordance with the observed abundance in fish hosts, being highest in the autumn and lowest during late winter and early summer. During summer, however, the estimated monthly transmission rates of C. truncatus were higher than the observed infection levels in the fish, suggesting restricted establishment success and shorter development time and longevity of the cestode in fish at higher temperatures. The accumulated transmission of C. farionis over the ontogeny of arctic charr was similar to the observed age‐specific infection levels, reflecting a high establishment success and longevity of this parasite in charr. In contrast, brown trout exhibited an infection level that was much lower than the estimated transmission rates, suggesting a high resistance against C. farionis in these fish. The magnitudes of the estimated transmission rates were sufficient to explain the paradoxical contrast between low infection levels in the intermediate and high in the final hosts.