bluuebunny/crossref_metadata_2025 huggingface dataset:
Testing the facilitation–competition paradigm under the stress-gradient hypothesis: decoupling multiple stress factors
Authors: Kawai Takashi , Tokeshi Mutsunori
Published: August 2007

While the facilitation–competition paradigm under the stress-gradient hypothesis has received recent attention, its rigorous testing is yet to be explored. Most of the studies have considered a switch in the net interactions from competition to facilitation with increasing environmental stress as primary evidence supporting the hypothesis, though few studies examined changes in interaction along a full range of a stress gradient. Here, we have conceptualized possible variations in the patterns of change in interaction strength along such gradient. Based on this, we empirically evaluated the temporal shift in the interaction between two marine sessile animals, goose barnacles (
Capitulum mitella
) and mussels (
Septifer virgatus
), under multiple stress factors. The net effect of goose barnacles on mussel survivorship was positively related to the total stress gradient encompassing two stress factors, physical disturbance and thermal stress, while no negative value occurred even under mild conditions. When the two stress factors were treated separately, however, the net effect demonstrated apparently different patterns: monotonic increase with physical disturbance versus a quasi-asymptotic pattern (no change over a wide range) with thermal stress. These variable situations have not previously been recognized in this discipline, and the present study emphasizes the importance of an integrative and mechanistic approach to testing and deciphering the facilitation–competition paradigm.
Coupled and forced patterns in reaction–diffusion systems
Authors: Epstein Irving R , Berenstein Igal B , Dolnik Milos , Vanag Vladimir K , Yang Lingfa , Zhabotinsky Anatol M
Published: August 2007

Several reaction–diffusion systems that exhibit temporal periodicity when well mixed also display spatio-temporal pattern formation in a spatially distributed, unstirred configuration. These patterns can be travelling (e.g. spirals, concentric circles, plane waves) or stationary in space (Turing structures, standing waves). The behaviour of coupled and forced temporal oscillators has been well studied, but much less is known about the phenomenology of forced and coupled patterns. We present experimental results focusing primarily on coupled patterns in two chemical systems, the chlorine dioxide–iodine–malonic acid reaction and the Belousov–Zhabotinsky reaction. The observed behaviour can be simulated with simple chemically plausible models.
Control of spatiotemporal chaos in catalytic CO oxidation by laser-induced pacemakers
Authors: Stich Michael , Punckt Christian , Beta Carsten , Rotermund Harm Hinrich
Published: August 2007

Control of spatiotemporal chaos is achieved in the catalytic oxidation of CO on Pt(110) by localized modification of the kinetic properties of the surface chemical reaction. In the experiment, a small temperature heterogeneity is created on the surface by a focused laser beam. This heterogeneity constitutes a pacemaker and starts to emit target waves. These waves slowly entrain the medium and suppress the spatiotemporal chaos that is present in the absence of control. We compare this experimental result with a numerical study of the Krischer–Eiswirth–Ertl model for CO oxidation on Pt(110). We confirm the experimental findings and identify regimes where complete and partial controls are possible.
Experimental observation of a torus doubling of a metal/ferroelectric film/semiconductor capacitor
Authors: Diestelhorst M , Barz K , Beige H , Alexe M , Hesse D
Published: August 2007

A metal–ferroelectric–semiconductor (MFS) structure was used as a nonlinear capacitor in a series resonance circuit. The following materials were used as components of the MFS structure: aluminium as the metal electrode, Bi
4
Ti
3
O
12
film as the ferroelectric, and p-type silicon as the semiconductor. The system was driven by a single frequency at suitably chosen amplitudes. Besides the sequences of period-doubling bifurcations which were already observed in the series resonance circuit with a pure ferroelectric capacitor, we found regions with torus-doubling bifurcations by varying the frequency of the driving voltage at suitably high amplitudes. Comparing the behaviour of the series resonance circuit with a pure ferroelectric capacitor and with the MFS structure, we attribute the reason for the new effect of torus doubling to the properties of the ferroelectric–semiconductor boundary layer.
Attractor selection in a modulated laser and in the Lorenz circuit
Authors: Meucci Riccardo , Salvadori Francesco , Naimee Kais Al , Brugioni Stefano , Goswami Binoy K , Boccaletti Stefano , Arecchi F. Tito
Published: August 2007

By tuning a control parameter, a chaotic system can either display two or more attractors (generalized multistability) or exhibit an interior crisis, whereby a chaotic attractor suddenly expands to include the region of an unstable orbit (bursting regime).

Recently, control of multistability and bursting have been experimentally proved in a modulated class B laser by means of a feedback method. In a bistable regime, the method relies on the knowledge of the frequency components of the two attractors. Near an interior crisis, the method requires retrieval of the unstable orbit colliding with the chaotic attractor.

We also show that a suitable parameter modulation is able to control bistability in the Lorenz system. We observe that, for every given modulation frequency, the chaotic attractor is destroyed under a boundary crisis. The threshold control amplitude depends on the control frequency and the location of the operating point in the bistable regime. Beyond the boundary crisis, the system remains in the steady state even if the control is switched off, demonstrating control of bistability.
Tracking the seasons: the internal calendars of vertebrates
Authors: Paul Matthew J , Zucker Irving , Schwartz William J
Published: August 2007

Animals have evolved many season-specific behavioural and physiological adaptations that allow them to both cope with and exploit the cyclic annual environment. Two classes of endogenous annual timekeeping mechanisms enable animals to track, anticipate and prepare for the seasons: a timer that measures an interval of several months and a clock that oscillates with a period of approximately a year. Here, we discuss the basic properties and biological substrates of these timekeeping mechanisms, as well as their reliance on, and encoding of environmental cues to accurately time seasonal events. While the separate classification of interval timers and circannual clocks has elucidated important differences in their underlying properties, comparative physiological investigations, especially those regarding seasonal prolactin secretions, hint at the possibility of common substrates.
The Leeuwenhoek lecture 2006. Microscopy goes cold: frozen viruses reveal their structural secrets
Authors: Crowther R.A
Published: August 2007

The electron microscope provides a powerful tool for investigating the structure of biological complexes such as viruses. A modern instrument is fully capable of atomic resolution on suitable non-biological specimens, but biological materials are difficult to preserve, owing to their fragility, and to image, owing to their radiation, sensitivity. The act of imaging the specimen severely damages it. Originally, samples were prepared by staining with a heavy metal salt, which provides a stable specimen but limits the amount of details that can be retrieved. Now particulate specimens, such as viruses, are prepared by rapid freezing of unstained material and observed in a frozen state with low doses of electrons. The resulting images require extensive computer processing to extract fully detailed three-dimensional information about the specimen. The whole process is referred to as single-particle electron cryomicroscopy. Using this approach, the structure of the human hepatitis B virus core was solved at the level of the protein fold. By comparing maps of RNA- and DNA-containing cores, it was possible to propose a model for the maturation and control of the envelopment of the virus during assembly. These examples show that cryomicroscopy offers great potential for understanding the structure and function of complex biological assemblies.
Biodiversity conservation and agricultural sustainability: towards a new paradigm of ‘ecoagriculture’ landscapes
Authors: Scherr Sara J , McNeely Jeffrey A
Published: August 2007

The dominant late twentieth century model of land use segregated agricultural production from areas managed for biodiversity conservation. This module is no longer adequate in much of the world. The Millennium Ecosystem Assessment confirmed that agriculture has dramatically increased its ecological footprint. Rural communities depend on key components of biodiversity and ecosystem services that are found in non-domestic habitats. Fortunately, agricultural landscapes can be designed and managed to host wild biodiversity of many types, with neutral or even positive effects on agricultural production and livelihoods. Innovative practitioners, scientists and indigenous land managers are adapting, designing and managing diverse types of ‘ecoagriculture’ landscapes to generate positive co-benefits for production, biodiversity and local people. We assess the potentials and limitations for successful conservation of biodiversity in productive agricultural landscapes, the feasibility of making such approaches financially viable, and the organizational, governance and policy frameworks needed to enable ecoagriculture planning and implementation at a globally significant scale. We conclude that effectively conserving wild biodiversity in agricultural landscapes will require increased research, policy coordination and strategic support to agricultural communities and conservationists.
Eco-efficient approaches to land management: a case for increased integration of crop and animal production systems
Authors: Wilkins R.J
Published: August 2007

Eco-efficiency is concerned with the efficient and sustainable use of resources in farm production and land management. It can be increased either by altering the management of individual crop and livestock enterprises or by altering the land-use system. This paper concentrates on the effects of crop sequence and rotation on soil fertility and nutrient use efficiency. The potential importance of mixed farming involving both crops and livestock is stressed, particularly when the systems incorporate biological nitrogen fixation and manure recycling. There is, however, little evidence that the trend in developed countries to farm-level specialization is being reduced. In some circumstances legislation to restrict diffuse pollution may provide incentives for more diverse eco-efficient farming and in other circumstances price premia for produce from eco-efficient systems, such as organic farming, and subsidies for the provision of environmental services may provide economic incentives for the adoption of such systems. However, change is likely to be most rapid where the present systems lead to obvious reductions in the productive potential of the land, such as in areas experiencing salinization. In other situations, there is promise that eco-efficiency could be increased on an area-wide basis by the establishment of linkages between farms of contrasting type, particularly between specialist crop and livestock farms, with contracts for the transfer of manures and, to a lesser extent, feeds.
Genetic contributions to agricultural sustainability
Authors: Dennis Elizabeth S , Ellis Jeffrey , Green Allan , Llewellyn Danny , Morell Matthew , Tabe Linda , Peacock W.J
Published: August 2007

The current tools of enquiry into the structure and operation of the plant genome have provided us with an understanding of plant development and function far beyond the state of knowledge that we had previously. We know about key genetic controls repressing or stimulating the cascades of gene expression that move a plant through stages in its life cycle, facilitating the morphogenesis of vegetative and reproductive tissues and organs. The new technologies are enabling the identification of key gene activity responses to the range of biotic and abiotic challenges experienced by plants. In the past, plant breeders produced new varieties with changes in the phases of development, modifications of plant architecture and improved levels of tolerance and resistance to environmental and biotic challenges by identifying the required phenotypes in a few plants among the large numbers of plants in a breeding population. Now our increased knowledge and powerful gene sequence-based diagnostics provide plant breeders with more precise selection objectives and assays to operate in rationally planned crop improvement programmes. We can expect yield potential to increase and harvested product quality portfolios to better fit an increasing diversity of market requirements. The new genetics will connect agriculture to sectors beyond the food, feed and fibre industries; agri-business will contribute to public health and will provide high-value products to the pharmaceutical industry as well as to industries previously based on petroleum feedstocks and chemical modification processes.
Optimizing nutrient management for farm systems
Authors: Goulding Keith , Jarvis Steve , Whitmore Andy
Published: August 2007

Increasing the inputs of nutrients has played a major role in increasing the supply of food to a continually growing world population. However, focusing attention on the most important nutrients, such as nitrogen (N), has in some cases led to nutrient imbalances, some excess applications especially of N, inefficient use and large losses to the environment with impacts on air and water quality, biodiversity and human health. In contrast, food exports from the developing to the developed world are depleting soils of nutrients in some countries. Better management of all essential nutrients is required that delivers sustainable agriculture and maintains the necessary increases in food production while minimizing waste, economic loss and environmental impacts. More extensive production systems typified by ‘organic farming’ may prove to be sustainable. However, for most of the developed world, and in the developing world where an ever-growing population demands more food, it will be essential to increase the efficiency of nutrient use in conventional systems. Nutrient management on farms is under the control of the land manger, the most effective of whom will already use various decision supports for calculating rates of application to achieve various production targets. Increasingly, land managers will need to conform to good practice to achieve production targets and to conform to environmental targets as well.
Associations of functional candidate genes derived from gene‐expression profiles of prenatal porcine muscle tissue with meat quality and muscle deposition
Authors: Wimmers K. , Murani E. , Te Pas M. F. W. , Chang K. C. , Davoli R. , Merks J. W. M. , Henne H. , Muraniova M. , Da Costa N. , Harlizius B. , Schellander K. , Böll I. , Braglia S. , De Wit A. A. C. , Cagnazzo M. , Fontanesi L. , Prins D. , Ponsuksili S.
Published: August 2007

Ten genes (ANK1, bR10D1, CA3, EPOR, HMGA2, MYPN, NME1, PDGFRA, ERC1, TTN), whose candidacy for meat‐quality and carcass traits arises from their differential expression in prenatal muscle development, were examined for association in 1700 performance‐tested fattening pigs of commercial purebred and crossbred herds of Duroc, Pietrain, Pietrain × (Landrace × Large White), Duroc × (Landrace × Large White) as well as in an experimental F2 population based on a reciprocal cross of Duroc and Pietrain. Comparative sequencing revealed polymorphic sites segregating across commercial breeds. Genetic mapping results corresponded to pre‐existing assignments to porcine chromosomes or current human–porcine comparative maps. Nine of these genes showed association with meat‐quality and carcass traits at a nominal P‐value of ≤ 0.05; PDGFRA revealed no association reaching the P ≤ 0.05 threshold. In particular, HMGA2, CA3, EPOR, NME1 and TTN were associated with meat colour, pH and conductivity of loin 24 h postmortem; CA3 and MYPN exhibited association with ham weight and lean content (FOM) respectively at P‐values of < 0.003 that correspond to false discovery rates of < 0.05. However, none of the genes showed significant associations for a particular trait across all populations. The study revealed statistical–genetic evidence for association of the functional candidate genes with traits related to meat quality and muscle deposition. The polymorphisms detected are not likely causal, but markers were identified that are in linkage disequilibrium with causal genetic variation within particular populations.
Lipoxin A4 levels in asthma: relation with disease severity and aspirin sensitivity
Authors: Çelik G. E. , Erkekol F. O. , Mιsιrlιgil Z. , Melli M.
Published: August 2007

Background
Lipoxin (LX) A4, an endogenous anti‐inflammatory eicosanoid, has been found to be low in patients with severe asthma. However, few studies also suggested more diminished LX A4 levels in aspirin‐exacerbated respiratory disease (AERD) when compared with aspirin‐tolerant asthma (ATA). It is, therefore, currently not clear whether the asthma severity or the presence of AERD has a primary role in the disturbed LX metabolism.

Objective
To detect LX A4 and 15‐epi‐LX A4 levels in asthma patients with and without AERD of comparable severity.

Methods
The study groups consisted of 22 subjects with AERD, 22 subjects with ATA and 10 volunteers without asthma and aspirin sensitivity. Whole‐blood samples were stimulated with calcium ionophore, A23187 (5 × 10−5 m) and A23187 (5 × 10−5 m)+aspirin (10−4 m). LX A4 and 15‐epi‐LX A4 levels were analysed by the enzyme immune assay method.

Results
Severe asthma patients in both AERD [0.5 (0.8)] ng/mL and ATA [0.5 (0.45) ng/mL] groups showed diminished generation for LX A4 to stimulation with A23187 in comparison with other severity degrees in their groups (P=0.02 and 0.046, respectively). LX A4 generation in both severe groups was comparable with each other (P>0.05). Although severe cases with AERD showed a diminished capacity to generate 15‐epi‐LX A4, this did not reach statistical significance.

Conclusion
This study indicated that diminished LX A4 generation was unique to severe asthma phenotype regardless of comorbid aspirin sensitivity.

Clinical Implications
Lower LX A4 levels in severe asthma would suggest a possibility for LX analogues as future treatment options in these patients.
What is the natural history of nonoperated nonfunctioning pituitary adenomas?
Authors: Karavitaki N. , Collison K. , Halliday J. , Byrne J. V. , Price P. , Cudlip S. , Wass J. A. H.
Published: August 2007

Background  Series of patients systematically investigating the outcome of clinically nonfunctioning pituitary adenomas (NFAs) not treated by surgery or radiotherapy during long follow‐up periods are limited. Most reports involve the follow‐up of selected cases of incidentally found lesions, rendering their results unreliable on the assessment of the pros and cons of a ‘watch and wait’ policy.

Objective  To investigate the outcome of a series of consecutive patients with presumed NFA (microadenoma or macroadenoma), who were not offered treatment at presentation (for a number of reasons) and were regularly followed up, and to identify possible factors predicting subsequent increase in tumour size.

Patients and methods  All patients presenting to the Department of Endocrinology in Oxford between 1989 and 2005 with presumed NFA were studied retrospectively. Inclusion criteria were: (i) imaging features suggestive of a pituitary adenoma, (ii) no clinical and/or biochemical evidence of hormonal hypersecretion by the tumour, (iii) monitoring being the initial choice of management, and (iv) at least one repeat scan during the follow‐up period. Subjects presenting with acute apoplexy were excluded. Follow‐up management included clinical evaluation, assessment of the visual acuity and fields and imaging at regular intervals. The duration of observation was estimated from the dates of first and last scan.

Results  Forty subjects were included in the study [18 males/22 females, median age 52 years (range 18–89), 16 with microadenoma/24 with macroadenoma]. The mean follow‐up period was 42 months (range 8–128). During the observation interval, 12·5% of the microadenomas and 50% of the macroadenomas increased in size. The 48‐month probability for enlargement was 19% for the microadenomas and 44% for the macroadenomas. Among the subjects with tumour enlargement, 57% showed new or worse visual field defects (all had macroadenomas) and 21% showed chiasmatic involvement on imaging without visual deterioration (all had macroadenomas). New or worse visual field defects were found in 67% of the macroadenomas showing increase in size. No microadenoma enlarged to cause visual deterioration. In microadenomas, sex and age at presentation were not predictors of enlargement. In macroadenomas, sex, age, visual field defects or cavernous sinus invasion at presentation were not predictors of enlargement.

Conclusions  The ‘watch and wait’ policy seems reasonable for microadenomas but is probably not a safe approach for macroadenomas, which appear to have a significant growth potential; in these cases, given the lack of established medical treatment, the decision for surgical intervention should balance the presence of significant comorbidities and the anaesthetic/peri‐operative risks at presentation against the probability of tumour enlargement and its consequences, as well as the possible loss of advantages associated with early operation.
Thyroid function and anti‐thyroid autoantibodies in untreated children with vertically acquired chronic hepatitis C virus infection
Authors: Indolfi Giuseppe , Stagi Stefano , Bartolini Elisa , Salti Roberto , De Martino Maurizio , Azzari Chiara , Resti Massimo
Published: August 2007

Objective  The reported data on thyroid function and anti‐thyroid autoantibodies in adults with untreated hepatitis C virus (HCV) infection are controversial. Data are scarce for HCV‐infected children, and only in those treated with interferon‐α (IFN‐α). We investigated thyroid function and anti‐thyroid autoantibodies in a cohort of untreated children with vertically acquired, chronic, HCV infection.

Design and patients  FT4 and TSH serum levels (measured by immunometric assays) and anti‐thyroglobulin (TgA) and anti‐thyroperoxidase (TPOA) antibodies (evaluated by fluorescence enzymatic immunoassays) were studied in 36 consecutive HCV‐infected children and 150 age‐ and sex‐matched controls. The prevalence of thyroid involvement was also related to family history of autoimmune disease, distribution of HCV genotypes, and duration and activity of HCV infection.

Results  Four out of 36 (11·1%) HCV‐infected children and 4/150 controls (2·7%) showed subclinical hypothyroidism [P = 0·04; relative risk (RR) 4·56, 95% confidence interval (CI) 1·08–19·21]. None of these had anti‐thyroid autoantibodies. Two out of 36 (5·6%) HCV‐infected children and 1/150 (0·7%) controls had increased TgA values with normal levels of TSH (P > 0·05). Subclinical hypothyroidism and anti‐thyroid autoantibodies were not related to family history of autoimmune disease, duration of infection, HCV viral load, liver function or different HCV genotype distribution, but seemed to be related to the presence of active HCV infection.

Conclusions  Our data suggest a role for HCV infection in the development of nonautoimmune thyroid disease in untreated HCV‐infected children, confirming previous studies in adults. Clinicians should be aware of thyroid dysfunction even in untreated children.
Multi-interferogram method for measuring interseismic deformation: Denali Fault, Alaska
Authors: Biggs Juliet , Wright Tim , Lu Zhong , Parsons Barry
Published: August 2007

Studies of interseismic strain accumulation are crucial to our understanding of continental deformation, the earthquake cycle and seismic hazard. By mapping small amounts of ground deformation over large spatial areas, InSAR has the potential to produce continental-scale maps of strain accumulation on active faults. However, most InSAR studies to date have focused on areas where the coherence is relatively good (e.g. California, Tibet and Turkey) and most analysis techniques (stacking, small baseline subset algorithm, permanent scatterers, etc.) only include information from pixels which are coherent throughout the time-span of the study. In some areas, such as Alaska, where the deformation rate is small and coherence very variable, it is necessary to include information from pixels which are coherent in some but not all interferograms. We use a three-stage iterative algorithm based on distributed scatterer interferometry. We validate our method using synthetic data created using realistic parameters from a test site on the Denali Fault, Alaska, and present a preliminary result of 10.5 ± 5.0 mm yr−1 for the slip rate on the Denali Fault based on a single track of radar data from ERS1/2.
Analysing two dinucleotide repeats of FVIII gene in Iranian population
Authors: RABBANI B. , REZAEIAN A. , KHANAHMAD H. , BAGHERI R. , KAMALI E. , ZEINALI S.
Published: August 2007

Summary.  Using dinucleotide repeats for carrier detection and prenatal diagnosis of haemophilia A patients, led us to find different alleles and their frequencies in Iranian population. Polymerase chain reaction (PCR) amplification of two short tandem repeat (STR) loci of factor VIII (FVIII) gene was performed, and the PCR products were resolved on 10% native polyacrylamide gel, and samples were analysed with sequenced DNA markers made of PCR cloning of the dinucleotide FVIII gene fragments. Seven different alleles were observed for intron 13 STR, having 18–24 (CA) repeating units and five alleles for intron 22 STR having 24–28 repeating units of (CACT). Bands produced during dinucleotide study were defined in detail so this could improve the genotyping of heterozygotes and homozygotes. Conformational band produced were characterized to specify the dinucleotide pattern. Our results confirm the Hardy–Weinberg proportions of the heterozygosity rate of the 85 analysed individuals. The observed heterozygosity rate for intron 13 and 22 was 52% and 59% respectively. Our data also indicate that our population is closer to caucasians than to any other populations. Finding different dinucleotide repeat alleles and their frequencies has made it possible to identify carriers and provide prenatal diagnosis with more confidence. This allows antenatal diagnosis to be performed in the vast majority of carriers.
A preliminary study investigating the survival of tetracycline resistant Enterococcus faecalis after root canal irrigation with high concentrations of tetracycline
Authors: Rossi‐Fedele G. , Roberts A. P.
Published: August 2007

Aim  To compare the ability of two Enterococcus faecalis strains to survive exposure to an irrigation solution containing a high concentration of tetracycline in the root canals of bovine teeth.

Methodology  The root canals of twelve bovine incisor root sections were chemo‐mechanically prepared using commercially available drills, sodium hypochlorite and ethylenediamine tetra‐acetic acid. The root sections were divided into two groups and inoculated with either a tetracycline sensitive or resistant strain of E. faecalis. The strains are isogenic, however one contains a conjugative transposon related to Tn916 which confers resistance to tetracycline, and the other strain is sensitive to the antibiotic. After 26 days of incubation the root canals were irrigated using one of three solutions (sterile distilled water, 50% ethanol or tetracycline at a concentration of 30 mg mL−1). The roots were sampled by grinding dentine and canal contents and the debris collected were incubated in broth to assess growth.

Results  Irrigation with sterile distilled water or 50% ethanol did not remove all of the cells present. The tetracycline containing solution was efficient in preventing any growth of sensitive E. faecalis, however the resistant strain was able to survive a 5 min exposure at 30 mg mL−1.

Conclusions  The presence of the Tn916‐like conjugative transposon containing the tetracycline resistance gene tet(M) allowed an E. faecalis strain to survive irrigation using a solution containing an extremely high concentration of tetracycline in a root canal model.
Effect of sodium hypochlorite on human root dentine – mechanical, chemical and structural evaluation
Authors: Marending M. , Luder H. U. , Brunner T. J. , Knecht S. , Stark W. J. , Zehnder M.
Published: August 2007

Aim  To investigate the mechanical, chemical and structural alterations of human root dentine following exposure to ascending sodium hypochlorite concentrations.

Methodology  Three‐point bending tests were carried out on standardized root dentine bars (n = 8 per group, sectioned from sound extracted human third molar teeth) to evaluate their flexural strength and modulus of elasticity after immersion in 5 mL of water (control), 1% NaOCl, 5% NaOCl or 9% NaOCl at 37 °C for 1 h. Additional dentine specimens were studied using microelemental analysis, light microscopy following bulk staining with basic fuchsin, and scanning electron microscopy (SEM). Numerical data were compared using one‐way anova. Bonferroni's correction was applied for multiple testing.

Results  Immersion in 1% NaOCl did not cause a significant drop in elastic modulus or flexural strength values in comparison to water, whilst immersion in 5% and 9% hypochlorite reduced these values by half (P < 0.05). Both, carbon and nitrogen contents of the specimens were significantly (P < 0.05) reduced by 5% and 9% NaOCl, whilst 1% NaOCl had no such effect. Exposure to 5% NaOCl rendered the superficial 80–100 μm of the intertubular dentine permeable to basic fuchsin. Three‐dimensional SEM reconstructions of partly demineralized specimens showed NaOCl concentration‐dependent matrix deterioration. Backscattered electron micrographs revealed that hypochlorite at any of the tested concentrations left the inorganic dentine components intact.

Conclusions  The current data link the concentration‐dependent hypochlorite effect on the mechanical dentine properties with the dissolution of organic dentine components.
The potential applications of cone beam computed tomography in the management of endodontic problems
Authors: Patel S. , Dawood A. , Ford T. Pitt , Whaites E.
Published: August 2007

Aim  To provide core information on cone beam computed tomography (CBCT) technology and its potential applications in endodontic practice.

Summary  CBCT has been specifically designed to produce undistorted three‐dimensional information of the maxillofacial skeleton as well as three‐dimensional images of the teeth and their surrounding tissues. This is usually achieved with a substantially lower effective dose compared with conventional medical computed tomography (CT). Periapical disease may be detected sooner using CBCT compared with periapical views, and the true size, extent, nature and position of periapical and resorptive lesions can be assessed. Root fractures, root canal anatomy and the true nature of the alveolar bone topography around teeth may be assessed. CBCT scans are desirable to assess posterior teeth prior to periapical surgery, as the thickness of the cortical and cancellous bone can be accurately determined as can the inclination of roots in relation to the surrounding jaw. The relationship of anatomical structures such as the maxillary sinus and inferior dental nerve to the root apices may also be clearly visualized.

Key learning points 

CBCT has a low effective dose in the same order of magnitude as conventional dental radiographs.

CBCT has numerous potential applications in the management of endodontic problems.
How students and instructors using a virtual learning environment perceive the fit between technology and task
Authors: McGill T.J. , Hobbs V.J.
Published: August 2007

Abstract Virtual learning environments (VLEs) are widespread in higher education today, typically used to deliver instructional materials and facilitate communication within a course. This study aimed to investigate the task–technology fit of VLEs for their two main groups of users: instructors and students, using the VLE WebCT. Task–technology fit, user satisfaction, attitude towards use and anticipated consequences of use were found to be significantly higher for students than for instructors. Instructors were found to have higher perceptions of social norms and higher perceptions of facilitating conditions than students. However, there was no difference between the instructors and students in level of utilization of the VLE. Students perceived that the VLE had higher impacts on their learning compared with instructors' perceptions regarding their teaching. These results suggest that despite high levels of support acknowledged by instructors, they may still be unsure about the contribution of VLEs to their teaching.
The oral health of people with intellectual disability participating in the UK Special Olympics
Authors: Turner S. , Sweeney M. , Kennedy C. , Macpherson L.
Published: August 2007

Background  Research on the dental health of people with intellectual disability has consistently reported more untreated dental disease, more extractions and fewer fillings than in the general population. This paper describes the oral health of participants at the 2005 Glasgow Special Olympics (SO), relating this to the general population studied in the 1998 UK Adult Dental Health Survey (ADHS) and to participants' age and region of residence.

Methods  Consenting SO participants were offered oral examinations which followed the standardized SO protocol plus an innovative soft tissue examination. Urgency of any treatment required was noted and reported to participants and carers. Three measures of good dental health – having 21 or more natural teeth, absence of fillings and having no obvious untreated decay – were compared across age groups, regions and with the general population. Logistic regression was used to control for age differences between regions.

Results  In total, 1021 oral examinations were completed. Older SO participants were more likely to have fewer than 21 teeth and to have fillings, untreated decay, gum inflammation and heavy plaque levels. In all, 28% of SO participants had 21 or more teeth, no fillings and no obvious decay. Those from the north, midlands and south regions of England had significantly more chance of good dental health so defined compared with participants from Scotland [ORs 1.67 (1.09, 2.67), 1.69 (1.12, 2.54), 1.99 (1.26, 3.16), respectively]. Compared with the general population surveyed in the 1998 ADHS study, SO participants were more likely to be free from fillings and obvious untreated decay, but fewer had 21 or more natural teeth among older age groups. Nine per cent were found to have soft tissue problems, and one in four of these required follow‐up. Gum inflammation was common. Overall, 5% of participants were judged to require urgent treatment for dental or soft tissue problems and 40% to require non‐urgent treatment. This rose to 9% and 66% respectively among those aged 35 years and over.

Discussion  The low prevalence of untreated decay and fillings among SO participants compared with the general population may be due to their being well supported by family and carers. The study identifies the vulnerability of the older participants to dental problems, and this may indicate greater difficulty maintaining surveillance as individuals age or informal carers become less able or available. Regional variations are similar to those found in the general population. The implications for the organization of care for this group are discussed.
A processive lipid glycosyltransferase in the small human pathogen Mycoplasma pneumoniae: involvement in host immune response
Authors: Klement Maria L. Rosén , Öjemyr Linda , Tagscherer Katrin E. , Widmalm Göran , Wieslander Åke
Published: August 2007

The human pathogen Mycoplasma pneumoniae has a very small genome but with many yet not identified gene functions, e.g. for membrane lipid biosynthesis. Extensive radioactive labelling in vivo and enzyme assays in vitro revealed a substantial capacity for membrane glycolipid biosynthesis, yielding three glycolipids, five phosphoglycolipids, in addition to six phospholipids. Most glycolipids were synthesized in a cell protein/lipid‐detergent extract in vitro; galactose was incorporated into all species, whereas glucose only into a few. One (MPN483) of the three predicted glycosyltransferases (GTs; all essential) was both processive and promiscuous, synthesizing most of the identified glycolipids. These enzymes are of a GT‐A fold, similar to an established structure, and belong to CAZy GT‐family 2. The cloned MPN483 could use both diacylglycerol (DAG) and human ceramide acceptor substrates, and in particular UDP‐galactose but also UDP‐glucose as donors, making mono‐, di‐ and trihexose variants. MPN483 output and processitivity was strongly influenced by the local lipid environment of anionic lipids. The structure of a major β1,6GlcβGalDAG species was determined by NMR spectroscopy. This, as well as other purified M. pneumoniae glycolipid species, is important antigens in early infections, as revealed from ELISA screens with patient IgM sera, highlighting new aspects of glycolipid function.
WaaL of Pseudomonas aeruginosa utilizes ATP in in vitro ligation of O antigen onto lipid A‐core
Authors: Abeyrathne Priyanka D. , Lam Joseph S.
Published: August 2007

waaL has been implicated as the gene that encodes the O‐antigen ligase. To date, in vitro biochemical evidence to prove that WaaL possesses ligase activity has been lacking due to the difficulty of purifying WaaL and unavailability of substrates. Here we describe the purification of WaaL, a membrane protein with 11 potential transmembrane segments from Pseudomonas aeruginosa, and the development of an in vitro O‐antigen ligase assay. WaaL was expressed in a P. aeruginosa wbpL knockout strain, which is defective in its initial glycosyltransferase for O‐antigen biosynthesis. This approach allowed the purification of WaaL without contaminating O‐antigen‐undecaprenol‐phosphate (Und‐P) molecules. Purified WaaL resolved to a monomer (35 kDa) and a dimer (70 kDa) band in SDS‐PAGE. The substrates for the O‐antigen ligase assay, O‐antigen‐Und‐P and lipid A‐core were prepared from a waaL mutant. ATP at 2–4 mM is optimum for the O‐ligase activity, and ATP hydrolysis by WaaL follows Michaelis–Menten kinetics. Site‐directed mutagenesis analysis indicated that the periplasmic loop region of WaaL is important for ligase activity. A waaL mutant of P. aeruginosa could not be cross‐complemented by waaL of Escherichia coli, which suggested that each of these proteins has specificity for its cognate core oligosaccharide.
Contribution to the search for binaries among Am stars – VIII. New spectroscopic orbits of eight systems and statistical study of a sample of 91 Am stars
Authors: Carquillat J.-M. , Prieur J.-L.
Published: August 2007

This paper is the last of a series devoted to the study of Am stars, with the monitoring of radial velocities of a sample of 91 objects during more than 20 yr. The purpose was to determine which stars were members of spectroscopic binaries (SBs) and study in detail those systems in order to obtain observational constraints on the origin of the Am phenomenon.

In the first part, we present the results of a detailed study of eight Am stars (HD 32893, 60489, 109762, 111057, 113697, 204918, 219675 and BD+44° 4512) observed at the Haute-Provence and Cambridge observatories with CORAVEL instruments. We find that these objects are single-lined SBs whose orbital elements are determined for the first time. HD 32893 is found to be a triple spectroscopic system whose third body might be detected by speckle interferometry. Physical parameters are inferred for the primaries of those SBs. We then investigate the influence of tidal interaction and find that it has already led to the synchronism of the primaries and to the circularization of the orbits of four of those systems.

In the second part of this paper, we present the main results of our whole programme and derive some statistical properties of Am stars. We give the recapitulating table of the orbital parameters found for the SBs of our whole sample and the list of those for which no evidence for radial velocity variations could be found during our monitoring. Our study shows that at least 64 per cent of Am stars are members of SBs. This rate is significantly greater than that of normal stars. Although some SBs may have been not detected, this study shows that a substantial fraction of Am stars do not belong to SBs: they are either isolated stars or members of wide binary systems.

We then present some statistical properties of the orbital parameters of the SBs whose primary is an Am star, on an extended sample obtained by adding 29 Am SB orbits published by other authors. The corresponding e versus log P diagram shows a cut-off between the circular and the eccentric systems at P≈ 5.6 ± 0.5 d, which indicates a typical age of 0.5 − 1 × 109 yr for the Am stars, which is in agreement with the values found in our previous detailed studies. A Monte Carlo analysis shows that the distribution of the mass function values f(m) is compatible with a power-law distribution N(m) ∝m−α of the masses m of the companions with α= 0.3 ± 0.2 or with a Gaussian distribution centred on 0.8 ± 0.5 M⊙, which indicates that the companions of Am SBs are mostly dwarf stars of type G-K-M.
Maternal dental history, child's birth outcome and early cognitive development
Authors: Daniels Julie L. , Rowland Andrew S. , Longnecker Matthew P. , Crawford Peter , Golding Jean ,   The ALSPAC Study Team
Published: August 2007

Prenatal exposure to high levels of mercury, radiation and inflammation have been associated with adverse reproductive outcomes such as increases in preterm delivery, low birthweight and delayed neurodevelopment. Few data are available to evaluate the potential effects of prenatal low‐level exposure to these factors as may occur during dental care. We evaluated maternal dental history prior to and during pregnancy in relation to birth outcomes and early communicative development among offspring in a large cohort (n = 7375) of British children born in 1991–92. Dental history was assessed by questionnaire. The child's communicative development was assessed using the MacArthur Communicative Development Inventory at 15 months of age. Total mercury was measured in umbilical cord tissue for a subset of the children.

Overall, dental care, including amalgam fillings, was not associated with birth outcomes or language development. Having X‐rays taken during pregnancy was not associated with birthweight measured continuously (b = 14.7, P = 0.4), but was associated with slightly increased odds of having a term, low‐birthweight baby (OR 1.9, [95% confidence interval 1.0, 3.4]). More detailed evaluation of the potential adverse effects of elective dental treatment during pregnancy, particularly dental X‐rays, may be warranted.
Maternal smoking, social class and outcomes of pregnancy
Authors: Villalbí Joan R. , Salvador Joaquin , Cano‐Serral Gemma , Rodríguez‐Sanz Maica C. , Borrell Carme
Published: August 2007

Exposure to tobacco during pregnancy is an important risk factor for infant health. Recently the prevalence of smoking during pregnancy has declined in our area. The objective of this study was to analyse the association between several social variables and the fetal exposure to smoking, as well as the association between maternal smoking and some adverse gestational outcomes. Data collection was cross‐sectional. The study population were women in the city of Barcelona (Catalonia, Spain) delivering a child without birth defects. The sample corresponded to the controls of the Birth Defects Registry of Barcelona, 2% of all pregnancy deliveries in the city from 1994 to 2003 (n = 2297). Information sources were hospital records and a personal interview of mothers. The analysis measured first the association between independent variables (instruction level, social class, occupation, nationality, planned pregnancy, parity, hospital funding and smoking status of the mother's partner) with two dependent variables: smoking at the initiation of pregnancy and quitting during pregnancy. Second, the persistence of smoking over pregnancy and all independent variables were studied with three variables indicating adverse outcomes of pregnancy: low gestation, low birthweight and intrauterine growth restriction (IUGR). Finally, the joint association between the persistence of smoking over pregnancy and social class taken as independent variables was determined with the three variables indicating adverse outcomes of pregnancy. Logistic regression models were fitted, adjusting for maternal age. Results are presented as odds ratios with their 95% confidence intervals.

The prevalence of smoking at the onset of gestation was 41%, and 40% of these women quit during pregnancy, so that 25% delivered as active smokers. Fewer women with higher educational levels and from families with non‐manual jobs smoked, as did immigrants, those planning pregnancy and women whose partner did not smoke. Smoking immigrants quit more frequently than nationals, as did those planning pregnancy, primiparae, and women whose partner did not smoke. Low gestation, low birthweight and IUGR were more frequent among smokers and women with a manual occupation, but manual occupation lost its significance when adjusting for smoking. The association between smoking and adverse results was higher for IUGR. In conclusion, the prevalence of smoking and quitting during pregnancy varied according to social factors. The influence of social factors on the outcome of pregnancy was mediated strongly by smoking in a country that provides access to health care free of cost. A priority in reducing inequalities in health is to help women from manual work backgrounds quit smoking.