bluuebunny/crossref_metadata_2025 huggingface dataset:
Prevalence of temporomandibular dysfunction in a group of scuba divers
Authors: Aldridge R D , Fenlon M R
Published: January 2004

Background:Temporomandibular dysfunction (TMD) has been reported to be a common problem in divers, with a prevalence of up to 68%. No evidence for this is available.

Objective:To investigate the prevalence of TMD in divers.

Method:Sixty three subjects were asked to retrospectively complete a questionnaire on symptoms of TMD after diving in warm and cold water areas and in daily life.

Results:The prevalence of TMD was greater in female divers. The prevalence of TMD while diving was about 26%, comparable to that experienced in daily life.

Conclusion:Improvements in mouthpiece design and lighter demand valves mean that TMD is now probably exacerbated by diving rather than caused by it.
Effect of physiotherapy attendance on outcome after anterior cruciate ligament reconstruction: a pilot study
Authors: Feller J A , Webster K E , Taylor N F , Payne R , Pizzari T
Published: January 2004

Background:In many centres patients are routinely referred for physiotherapy after anterior cruciate ligament (ACL) reconstruction. However, to date the role and amount of supervised physiotherapy required has not been clearly established.

Objective:To establish whether there was any difference in outcome between a group of patients who attended physiotherapy regularly after ACL reconstruction and a group who attended only infrequently.

Methods:Ten patients who had attended physiotherapy infrequently (mean 1.9 visits) during the first six months after ACL reconstructive surgery were matched for age, sex, graft type, and activity level and occupation before injury with 10 patients who had attended physiotherapy regularly (mean 26.5 visits). Outcome was assessed at 12 months using the Cincinnati knee rating system and the IKDC form.

Results:Compared with the regular physiotherapy group, patients in the minimal physiotherapy group had fewer symptoms (mean Cincinnati symptom score 46.2v43.4, p  =  0.045). There was alsoatrend towards higher overall Cincinnati knee scores in the minimal physiotherapy group (mean 93.7v87.3, p  =  0.06) but no difference in IKDC ratings.

Conclusion:These preliminary results indicate that some patients who choose to attend physiotherapy on a very limited basis after ACL reconstruction can achieve satisfactory, if not better, outcomes than patients who attend physiotherapy regularly.
Raised concentrations of C reactive protein in anabolic steroid using bodybuilders: Table 1
Authors: Grace F M , Davies B
Published: January 2004

Objective:To examine levels of C reactive protein in users of anabolic androgenic steroids (AAS) compared with age matched control groups consisting of AAS using (but abstinent)/resistance trained and non-drug using/sedentary controls.

Method:Subjects included AAS using bodybuilders (n  =  10); bodybuilders who denied AAS use (n  =  10); sedentary controls (n  =  8). Venous blood was sampled, from which serum concentrations of C reactive protein, male sex hormones, and cardiac troponin T were determined.

Results:A significantly altered hormonal profile in the AAS using group provided indirect confirmation of AAS use. C reactive protein concentrations were significantly (p<0.05) higher in the AAS using bodybuilders. There was no relation between C reactive protein and cardiac troponin T.

Conclusion:AAS using bodybuilders had significantly higher C reactive protein concentrations, indicating a greater propensity to develop peripheral arterial disease.
Regular Papers / Articles OrdinairesIntine wall modifications during germination ofZygophyllum fabago(Zygophyllaceae) pollen grains
Authors: Castells Teresa , Seoane-Camba Juan A , Suárez-Cervera María
Published: January 2004

The composition of the inner layer (intine) of mature, activated, and germinated Zygophyllum fabago L. (Zygophyllaceae) pollen grains was studied. Cytochemical techniques showed neutral and acidic polysaccharides to be the major component of the thin and unlayered intine. The intine lacks lipids, with only scattered lipid globules being observed near the plasma membrane. Immunocytochemical localization of esterified and unesterified pectins in the intine was performed to determine the behaviour (permeability and elasticity) of germinal apertures. The high density of unesterified pectins in the intine of Z. fabago may be related to harmomegathic changes, which increase the elasticity of the intine during hydration and germination processes. A new layer was deposited in germinated pollen grains, recognized by 1,3-β-glucan (callose) antibodies; this layer plays a role in keeping the grains swollen during the germination process and probably forms a selective barrier to control the movement of substances through the pollen walls. Indeed, the composition of the Z. fabago intine was related to both the hydration process preceding germination and the passage of allergenic proteins through it.Key words: callose, germination, intine, pectins, pollen grains, Zygophyllum fabago.
Antifreeze proteins from snow mold fungi
Authors: Hoshino Tamotsu , Kiriaki Michiko , Ohgiya Satoru , Fujiwara Mineko , Kondo Hidemasa , Nishimiya Yoshiyuki , Yumoto Isao , Tsuda Sakae
Published: January 2004

The psychrophilic fungi Coprinus psychromorbidus and Typhula ishikariensis produced unique antifreeze proteins (AFPs) in the extracellular space. Molecular masses of purified fungal AFPs of C. psychromorbidus and T. ishikariensis were approximately 22 and 23 kDa, respectively. Cloned genes of AFPs from T. ishikariensis do not have any similarity with known proteins. Purified fungal AFPs from cultural filtrate of T. ishikariensis and recombinant fungal AFP from methylotrophic yeast formed specific ice crystals resembling "Stone Age knives". These observations indicate that fungal AFPs do not form proper hexagonal ice crystals to inhibit their growth and that fungal AFPs can probably bind to surfaces of ice crystals in an irregular manner.Key words: antifreeze protein, snow mold fungi, Coprinus psychromorbidus, Typhula ishikariensis.
Seasonal differences in plant responses to flooding and anoxia
Authors: Crawford R MM
Published: January 2004

Strategies for surviving an environmental stress in winter can differ from those that provide protection from the same stress when it occurs in summer. During the growing season, escape mechanisms from stresses tend to prevail, as periods of adversity are generally brief. In winter, adverse environmental conditions have a high probability of persisting for lengthy periods and consequenctly, survival depends on tolerance. Spring is a period of uncertainty as to whether the risk of flooding has passed, and seeds differ markedly in their ability to resume germination if interrupted by re-imposition of winter conditions. When growing plants are flooded in summer, brief periods of accelerated anaerobic metabolism can alleviate energy shortages while improved aeration tissues develop, which then remove the dangers of prolonged anaerobiosis. By contrast, overwintering species, if they are highly tolerant of prolonged anoxia, may down-regulate metabolism when flooded and thus reduce the risk of exhausting carbohydrate supplies. Ventilation of underground organs in winter is still possible but is dependent on specialized mechanisms that can provide a through flow of air from emergent stems to buried or submerged organs. The tree form also presents metabolic and morphological problems for surviving wet conditions at critical seasons.Key words : anoxia, flooding summer, winter stress, plants, crops.
The species complex of Gremmeniella abietina - intertype hybridization, viruses, and gene flow in northern Europe
Authors: Hantula Jarkko , Tuomivirta Tero T
Published: January 2004

In this paper we review the available information on the possibility of gene flow between the European types A and B of Gremmeniella abietina (Lagerb.) Morelet. In nature, types A and B may have mycelial interactions in pine seedlings and lower branches covered by snow during winter. In artificial conditions, the two types are able to produce low-fitness hybrids. The distinct virus populations of the two types, however, suggest that the importance of any possible hybridization in nature is negligible.Key words: interspecific mating, introgression, dsRNA.
Plant adaptations to overwintering stresses and implications of climate change
Authors: Bertrand Annick , Castonguay Yves
Published: January 2004

Winter survival is a complex trait that does not solely rely on the plant's ability to withstand the direct effects of extreme cold temperatures. During long overwintering periods, plants are exposed to multiple abiotic (ice encasement, frost heave, desiccation, anoxia) and biotic (snow mould and other psychrophylic pathogens) stresses. Tolerance to these various stresses is based in part on shared adaptive traits and, consequently, cross-adaptation to environmental stresses is a key aspect of plant adaptation to cold. Increasing evidence of multiple functions for stress-induced proteins in overwintering plants confirms the need for a global approach in the analysis of adaptive mechanisms. From that perspective, the valorization of rapidly increasing knowledge on the molecular and genetic basis of plant and microbe adaptations to cold will demand multidisciplinary collaborations. Climate change will also need to be taken into account to identify the adaptive traits that will be required for agricultural and forest plants to survive winter in the future. More studies at the global and regional scales will be needed to assess the potential impact of climate warming on plant adaptation to winter and their interactions with low-temperature pathogens.Key words: cold adaptation, psychrophylic microorganisms, climate change, fall dormancy, low-temperature plantmicrobe interactions, cold-adaptation genomics.
From genotype to phenotype: unraveling the complexities of cold adaptation in forest trees
Authors: Howe Glenn T , Aitken Sally N , Neale David B , Jermstad Kathleen D , Wheeler Nicholas C , Chen Tony HH
Published: January 2004

Adaptation to winter cold in temperate and boreal trees involves complex genetic, physiological, and developmental processes. Genecological studies demonstrate the existence of steep genetic clines for cold adaptation traits in relation to environmental (mostly temperature related) gradients. Population differentiation is generally stronger for cold adaptation traits than for other quantitative traits and allozymes. Therefore, these traits appear to be under strong natural selection. Nonetheless, high levels of genetic variation persist within populations. The genetic control of cold adaptation traits ranges from weak to strong, with phenological traits having the highest heritabilities. Within-population genetic correlations among traits range from negligible to moderate. Generally, bud phenology and cold hardiness in the fall are genetically uncorrelated with bud phenology and cold hardiness in the spring. Analyses of quantitative trait loci indicate that cold adaptation traits are mostly controlled by multiple genes with small effects and that quantitative trait loci × environment interactions are common. Given this inherent complexity, we suggest that future research should focus on identifying and developing markers for cold adaptation candidate genes, then using multilocus, multi allelic analytical techniques to uncover the relationships between genotype and phenotype at both the individual and population levels. Ultimately, these methods may be useful for predicting the performance of genotypes in breeding programs and for better understanding the evolutionary ecology of forest trees.Key words: association genetics, cold hardiness, dormancy, genecology, bud phenology, quantitative trait loci.
Simulation of the comparative gains from four different hybrid tree breeding strategies
Authors: Kerr R J , Dieters M J , Tier B
Published: January 2004

There is increasing interest in the deployment of interspecific hybrids in forest tree planting. The associated breeding programs are usually an adaptation of the reciprocal recurrent selection (RRS) strategy outlined by Comstock et al. (R. Comstock, H. Robonson, and P. Harvey. 1949. Agron. J. 41: 360367) or use recurrent selection for general combining ability (GCA) in the pure species. This study uses a computer simulation tool known as XSIM, which has been described in a previous paper, to investigate the efficiency of four hybrid strategies. In addition to conventional RRS, we considered RRS with forward selection (RRS-SF), a strategy that approximately halves the generation interval needed for RRS, because hybrid and pure species progeny are bred simultaneously. Forward and backward selections are also made simultaneously and not in successive generations as is the case for RRS. An innovative best linear unbiased prediction analysis makes this possible. The development of a synthetic species (SYN) and pure species selection (PSS) were other strategies tested. The strategies were tested across a wide range of genetic structures. Genetic structures were defined as particular combinations of the correlation between pure species and hybrid performance for each species and the proportion of the genetic variance that is additive, dominance, and epistatic for each species. The results of the simulation have shown that the SYN strategy is the most cost effective across a wider range of genetic structures. This is especially so for those structures where there is less dominance variance and the purehybrid correlations in both species are greater than zero. Where the SYN strategy is not cost effective, the RRS-SF strategy is then the best option.
Application of near-infrared spectroscopy for the detection of internal insect infestation inPiceaabiesseed lots
Authors: Tigabu Mulualem , Odén Per Christer , Shen Tong Yun
Published: January 2004

The use of near-infrared (NIR) spectroscopy to discriminate between uninfested seeds of Picea abies (L.) Karst and seeds infested with Plemeliella abietina Seitn (Hymenoptera, Torymidae) larva is sensitive to seed origin and year of collection. Five seed lots collected during different years from Sweden, Finland, and Belarus were used in this study. Initially, seeds were classified as infested or uninfested with X-radiography, and then, NIR spectra from single seeds were collected with a NIR spectrometer from 1100 to 2498 nm with a resolution of 2 nm. Discriminant models were derived by partial least squares regression using raw and orthogonal signal corrected spectra (OSC). The resulting OSC model developed on a pooled data set was more robust than the raw model and resulted in 100% classification accuracy. Once irrelevant spectral variations were removed by using OSC pretreatment, single-lot calibration models resulted in similar classification rates for the new samples irrespective of origin and year of collection. Dis criminant analyses performed with selected NIR absorption bands also gave nearly 100% classification rate for new samples. The origin of spectral differences between infested and uninfested seeds was attributed to storage lipids and proteins that were completely depleted in the former by the feeding larva.
Seed cone traits and insect damage in Tsuga canadensis (Pinaceae)
Authors: Turgeon Jean J , Jones Chuck , Bellocq M Isabel
Published: January 2004

We measured seed cones of Tsuga canadensis (L.) Carrière, assessed seed potential (number of fertile scales × 2) and seed efficiency (number of filled seeds/seed potential), and estimated the impact of Eupithecia mutata Pearsall (Lepidoptera: Geometridae) and Megastigmus hoffmeyeri Walley (Hymenoptera: Torymidae) on seed production. Mean length, width, and volume of healthy cones varied little among sites from Ontario. Cones had about 28 scales; 13 were sterile. Seed potential and seed efficiency differed among sites, ranging from 25 to 31 ovules and 24% to 72%, respectively. The number of scales (both sterile and fertile) increased with cone volume, but the proportion of fertile scales was independent of cone size. The maximum proportion of cones infested by E. mutata was 21%. On average, each larva destroyed >90% of the filled seeds from each cone, thus from a practical perspective, the proportion of T. canadensis seeds destroyed per site was equivalent to the proportion of seed cones infested. The proportion of cones infested by M. hoffmeyeri ranged from 9% to 40%, but the proportion of seeds destroyed per site (range: 1.1%6.1%) was much lower than that of E. mutata. The maximum number of M. hoffmeyeri-infested seeds per cone was seven. To our knowledge, this is the first report documenting cone traits of T. canadensis and the impact of E. mutata and M. hoffmeyeri.
Bedrock type significantly affects individual tree mortality for various conifers in the inland Northwest, U.S.A.
Authors: Moore James A , Hamilton Jr. David A , Xiao Yu , Byrne John
Published: January 2004

Individual tree mortality models for western white pine (Pinus monticola Dougl. ex D. Don), Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), grand fir (Abies grandis (Dougl. ex D. Don) Lindl.), western redcedar (Thuja plicata Donn ex. D. Don), western hemlock (Tsuga heterophylla (Raf.) Sarg.), and western larch (Larix occidentalis Nutt.) were developed using data from permanent research plots located throughout the inland Northwest. The proposed linear logistic models included the following independent variables: diameter at breast height, basal area in larger trees, basal area per hectare, individual tree diameter increment, and a set of dummy variables for the six bedrock types, which were granite, basalt, metasedimentary, sedimentary, mixed  glacial till, and deep deposit. The results show that rock type significantly affects individual tree mortality for western white pine, Douglas-fir, and western redcedar, while grand fir, western hemlock, and western larch were not affected. Western white pine and Douglas-fir growing on meta sedimentary rocks exhibited greater mortality probabilities than on other rocks. Mortality probabilities for western hemlock were low across all rock types, including "nutrient-poor" rocks like metasedimentary types.
Light and temperature differentially colimit subalpine fir and Engelmann spruce seedling growth in partial-cut subalpine forests
Authors: Lajzerowicz Cleo C , Walters Michael B , Krasowski Marek , Massicotte Hugues B
Published: January 2004

We compared the relative impacts of light, soil N, and soil temperature on Engelmann spruce (Picea engelman nii Parry ex Engelm.) and subalpine fir (Abies lasiocarpa (Hook.) Nutt.) seedling growth by quantifying (i) microsite environment-growth relationships for N-fertilized and unfertilized planted seedlings in shelterwood, patch cut, and clearcut harvest treatments and (ii) growth, photosynthesis, and biomass allocation for greenhouse-grown seedlings at 5, 10, and 15 °C soil temperatures. Fertilization did not affect seedling growth. Furthermore, soil N availability did not vary among harvest treatments. In contrast, clearcut compared with shelterwood seedlings had greater mass (fivefold), light availability (twofold), and soil temperatures (1.6 °C). Across harvest treatments, spruce and fir mass increased linearly to 100% open-sky light (R2 = 0.51 and 0.57, respectively), and temperature and light combined explained more variation in mass than light alone (adjusted R2 = 0.58 for both species). Spruce growth was more sensitive to temperature than fir in both field and greenhouse experiments. Diminished growth at low soil temperature was associated with lower photosynthesis and not lower leaf fraction. Thus, soil temperature and light colimit seedling growth in subalpine forests, but responses were species-specific and consistent with microenvironment differences in spruce and fir regeneration niches.
Interregional nonlinear heightdiameter model with random coefficients for stone pine in Spain
Authors: Calama Rafael , Montero Gregorio
Published: January 2004

An individual-tree heightdiameter model was developed for stone pine (Pinus pinea L.) in Spain. Five biparametric nonlinear equations were fitted and evaluated based on a data set consisting of 8614 trees from 455 plots located in the four most important regions where the species occurs in Spain. Because of the problem of high correlation among observations taken from the same sampling unit, a mixed-model approach, including random coefficients, is proposed. Several stand variables, such as density, dominant height, or diametric distribution percentiles, were included in the model as covariates to explain among plot variability. To determine interregional variability among the regions studied, regional effects were included in the model using fixed dummy variables. Two models, one for inland regions and one for coastal regions, were found to be sufficient to explain regional variability in the heightdiameter relationship for the species in Spain. Mixed models allow predictive role in two ways: a typical response, including only fixed effects, and a calibrated response, where random effects are predicted and included in the model from the prior measurement of the height in a subsample of trees. Different alternatives were tested to determine optimum subsample size. Measurement of the height of the 20% largest trees in the plot has been shown to be a useful approach.
Planting Betula pendula on pine sites infested by Heterobasidion annosum: disease transfer, silvicultural evaluation, and community of wood-inhabiting fungi
Authors: Lygis Vaidotas , Vasiliauskas Rimvydas , Stenlid Jan
Published: January 2004

Persistence of the root rot pathogen Heterobasidion annosum (Fr.) Bref. s.s. on infested areas and its transfer to a forest regeneration was studied in three forest sites in eastern Lithuania. The sites represented H. annosum disease centres in Pinus sylvestris L. stands, which were clear-felled and replanted with Betula pendula Roth 25 years prior to our study. Fungal isolation from trees and stumps on each site was performed on both replanted B. pendula and surrounding P. sylvestris from the previous generation. Low productivity of B. pendula stands (45.076.1 m3·ha1), high mortality rates, and comparatively low vigor of trees (measured as crown densities) indicated a strong impact of root rot. Based on somatic incompatibility tests, we detected large spreading areas of clones of H. annosum (up to 48 m across) and old (35- to 40-year-old) clonal individuals. Territorial clones covered areas that encompassed both previous stands of P. sylvestris and current stands of B. pendula. Our results showed that H. annosum is able to persist in root systems of diseased trees for decades and readily attack birch replanted on infested sites. In addition, a total of 83 fungal species (out of 398 isolates) was found as a result of sampling 508 B. pendula, 49 P. sylvestris, 21 Juniperus communis L., and 1 Salix cinerea L. trees.
Reproductive capacity of the grey pine aphid and allocation response of Scots pine seedlings across temperature gradients: a test of hypotheses predicting outcomes of global warming
Authors: Holopainen Jarmo K , Kainulainen Pirjo
Published: January 2004

The effects of the expected increase in growing season temperature on the performance of the aphid Schizolachnus pineti (Fabricius) (Homoptera: Lachnidae) and on the nutritional quality of its host plant (Pinus sylvestris L.) were studied under a daytime temperature range of 2028 °C, with nighttime temperature that was either fixed at 12 °C or 8 °C below the daytime temperature. Fecundity had a curvilinear response, with an optimum at 24 or 26 °C, which is 4 to 6 °C above the local mean daytime temperatures. Longevity of nymphal stage was negatively and linearly correlated (r2 = 0.967) with daytime temperature. Intrinsic rate of population increase (rm) and relative growth rate were significantly higher at 26 °C than at 20 °C. Fecundity and rm were negatively correlated with total phenolic concentration in needles. Temperature affected concentrations of some individual resin acids in needles and stems, while concentrations of monoterpenes, total phenolics, starch, and total nitrogen in needles were not affected by temperature. Seedlings grown at 24 °C achieved the greatest biomass. Results support the protein competition hypothesis, which predicts no changes in the concentration of plant phenolics with small temperature increases. However, at 26 °C the low starch/nitrogen ratio and low total phenolic concentration may partly explain increased fecundity of aphids.
Effect of tree mixture on the humic epipedon and vegetation diversity in managed beech forests (Normandy, France)
Authors: Aubert Michaël , Bureau Fabrice , Alard Didier , Bardat Jacques
Published: January 2004

Using a space-for-time substitution procedure, we assessed the patterns of variation during stand development of the humic epipedon and vegetation diversity in a pure European beech (Fagus sylvatica L.) forest and in a mixed beechhornbeam (Carpinus betulus L.) forest. The humic epipedon was investigated through macro morpho logical characteristics (thickness of the OL, OF, OH, and A horizons) and pH measurements (pHKCl, pHH20, and ΔpH). Vegetation diversity was assessed using correspondence analysis and hierarchical cluster analysis to identify the main plant community succession groups. The groups were compared using three diversity measures (species richness, Shannon index, and evenness index) and three indices describing the community composition (similarity index between stands and index of heterogeneity at the stand and herbaceous layer levels). The pH measurements revealed an acidification of the A horizon during pure beech stand maturation. Macromorphological characteristics showed an alternation of an organic matter accumulation phase and organic matter disappearance along the two silvicultural cycles. Vegetation diversity measures showed small differences between the two forests. Indices accounting for community composition revealed a homogenizing effect of the pure beech silvicultural type on species composition of plant communities occurring during stand development. They also revealed a strong heterogeneity at the herbaceous level. Comparison of species composition indicated an increasing occurrence of acidophilous species in the pure beech forest. We discuss the interest of these results for future sustainable management decisions.
A longitudinal height–diameter model for Norway spruce in Finland
Authors: Mehtätalo Lauri
Published: January 2004

A height–diameter (HD) model for Norway spruce (Picea abies (L.) Karst.) was estimated from longitudinal data. The Korf growth curve was used as the HD curve. Firstly, HD curves for each stand at each measurement time were fitted, and the trends in the parameters of the HD curve were modeled. Secondly, the trends were included in the HD model to estimate the whole model at once. To take the hierarchy of the data into account, a mixed-model approach was used. This makes it possible to calibrate the model for a new stand at a given point in time using sample tree height(s). The heights may be from different points in time and need not be from the point in time being predicted. The trends in the parameters of the HD curve were not estimated as a function of stand age but as a function of the median diameter of basal area weighted diameter distribution (dGm). This approach was chosen because the stand ages may differ substantially among stands with similar current growth patterns. This is true especially with shade-tolerant tree species, which can regenerate and survive for several years beneath the dominant canopy layer and start rapid growth later. The growth patterns in stands with a given dGm, on the other hand, seem not to vary much. This finding indicates that the growth pattern of a stand does not depend on stand age but on mean tree size in the stand.
FERMION MASSES AND MIXING AND CP-VIOLATION IN SO(10) MODELS WITH FAMILY SYMMETRIES
Authors: CHEN MU-CHUN , MAHANTHAPPA K. T.
Published: January 2004

Several ideas for solving the problem of fermion mass hierarchy and mixing and specific supersymmetric models that realize it are reviewed. In particular, we discuss many models based on SO(10) in four dimensions combined with a family symmetry to accommodate fermion mass hierarchy and mixing, including the case of neutrinos. These models are compared and various tests that can be used to distinguish these models are suggested. We also include a discussion of a few SO(10) models in higher space–time dimensions.
Quantization conditions and p–form electrodynamics
Authors: Chruściński Dariusz
Published: January 2004

We show that there is a striking correspondence between the quantization conditions for p-brane dyons and the corresponding canonical structure for a p-form electrodynamics. The distinguished role played by the Born-Infeld theory is outlined.
Quantum Field Theory of Open Spin Networks and New Spin Foam Models
Authors: Miković A.
Published: January 2004

We describe how a spin-foam state sum model can be reformulated as a quantum field theory of spin networks, such that the Feynman diagrams of that field theory are the spin-foam amplitudes. In the case of open spin networks, we obtain a new type of state-sum models, which we call the matter spin foam models. In this type of state-sum models, one labels both the faces and the edges of the dual two-complex for a manifold triangulation with the simple objects from a tensor category. In the case of Lie groups, such a model corresponds to a quantization of a theory whose fields are the principal bundle connection and the sections of the associated vector bundles. We briefly discuss the relevance of the matter spin foam models for quantum gravity and for topological quantum field theories.
COMPUTER ASSISTED CHARACTERIZATION OF RAPID REPETITIVE ELECTRICAL ACTIVATIONS IN THE PULMONARY VEINS DURING ATRIAL FIBRILLATION
Authors: LANGLEY P. , O'DONNELL D. , RAINE D. , FURNISS S. S. , BOURKE J. P. , MURRAY A.
Published: January 2004

Our group has described previously the identification of arrhythmogenic pulmonary veins by rapid local electrical activations during atrial fibrillation. We have now investigated an algorithm for automated computer detection of this phenomenon from catheter electrodes in the upper pulmonary veins and assessed its performance in identifying arrhymogenic veins. Ten patients with persistent atrial fibrillation scheduled for pulmonary vein isolation at this hospital were studied. Electrogram recordings in the upper pulmonary veins were recorded and analyzed. Arrhythmogenic veins were identified by focal activity during sinus rhythm at electrophysiological studies. Recordings were visually assessed by a cardiologist for the presence of rapid repetitive electrical activations during atrial fibrillation. An index of rapid repetitive electrical activity (RREA index), the ratio of the number of activations with cycle lengths in the range 50 ms to 100 ms to the number of activations with cycle lengths in the range 100 ms to 200 ms, was devised to describe the extent of such activity automatically. The index was assessed as a predictor of arrhythmogenic veins. Electrograms from 19 upper pulmonary veins were recorded. Rapid activity was evident in 15 veins by visual manual assessment. The mean (range) automatic RREA index was 0.07 (0 to 0.16) for those identified as having no such activity manually, and 0.83 (0.22 to 1.68) for those identified with rapid activity (p<0.0001). With a threshold of RREA index in the range 0.17 to 0.21, the identification of veins with rapid firing was exactly the same as for manual assessment. Eleven upper pulmonary veins were identified as arrhythmogenic during electrophysiological study, and the identification of these veins by both manual and automatic assessment of rapid repetitive electrical activations gave a sensitivity of 100% (11/11) and specificity of 50% (4/8). A technique for automatic characterization of electrogram cycle length has been demonstrated and could be used online as a tool for identifying candidate sites for pulmonary vein isolation in patients despite persistent atrial fibrillation.
STRUCTURE-FUNCTION RELATIONSHIPS OF THE SINOATRIAL NODE
Authors: DOBRZYNSKI HALINA , ZHANG HENGGUI , WRIGHT SALLY E. , HOLDEN ARUN V. , BOYETT MARK R.
Published: January 2004

The sinoatrial node, the pacemaker of the heart, is a structurally and functionally complex and heterogeneous structure. Histology, immunohistochemistry, electrophysiology and mathematical modeling of the sinoatrial node are reviewed to reveal the structure-function relationships of the sinoatrial node. It is argued that contact between the sinoatrial node and surrounding atrial muscle is limited to permit driving of the atrial muscle by the sinoatrial node but not suppression of the sinoatrial node by the atrial muscle (which is more hyperpolarized). It is argued that a protective conduction block zone on one side of the sinoatrial node is the result of a lack of myocytes. Finally, it is argued that the cellular organization of the sinoatrial node is best described by the gradient model.
ADVANCES IN MODELING CARDIAC DEFIBRILLATION
Authors: AGUEL FELIPE , EASON JAMES , TRAYANOVA NATALIA
Published: January 2004

This paper presents the development of a bidomain model of electrical defibrillation and post-shock arrhythmogenesis of the rabbit heart. The model incorporates a realistic representation of cardiac geometry, fiber structure, and membrane ionic processes. Fibrillation is induced in the rabbit heart with burst pacing. Defibrillation shocks of various strengths are delivered to the model in an attempt to terminate the arrhythmia. Two sets of defibrillation simulations are conducted based on the waveform of the defibrillation shock: monophasic and biphasic. The simulations presented here demonstrate the feasibility of modeling realistically the effect of the defibrillation shock on the heart.
MATHEMATICAL MODELING OF CARDIAC ELECTRO-MECHANICS: FROM PROTEIN TO ORGAN
Authors: SACHSE FRANK B. , SEEMANN GUNNAR , MOHR MATTHIAS B. , HOLDEN ARUN V.
Published: January 2004

Mathematical models of cardiac anatomy and physics provide information, which help to understand structure and behavior of the heart. Miscellaneous cardiac phenomena can only be adequately described by combination of models representing different aspects or levels of detail. Coupling of these models necessitates the definition of appropriate interfaces. Adequateness and efficiency of interfaces is crucial for efficient application of the combined models.

In this work an integrated model is presented consisting of several models interconnected by interfaces. The integrated model allows the reconstruction of macroscopic electro-mechanical processes in the heart. The model comprises a three-dimensional are of left ventricular anatomy represented as truncated ellipsoid. The integrated model includes electrophysiological, tension development and elastomechanical models of myocardium at levels of single cell, proteins, and tissue patches, respectively.

The model is exemplified by simulations of extracorporated left ventricle of small mammals. These simulations yield temporal distributions of electrophysiological parameters as well as descriptions of electrical propagation and mechanical deformation. The simulations show characteristic macroscopic ventricular function resulting from the interplay between cellular electrophysiology, electrical excitation propagation, tension development, and mechanical deformation.
MODELING OF WOLFF–PARKINSON–WHITE SYNDROME
Authors: HINCH ROBERT
Published: January 2004

Wolff–Parkinson–White syndrome is a disease where an arrhythmia is caused by the ventricles being electrically excited by an additional accessory pathway that links the atria to the ventricles. The spread of the activation wave from this pathway to the ventricles is modeled using a simplified model of Hodgkin–Huxley sodium channel kinetics, in a two ion-channel model. The model is investigated both analytically (using an asymptotic analysis) and numerically, and both methods are shown to give the same result. It is found that for a given width of the accessory pathway, there is a critical sodium channel density needed for the activation wave to spread from the pathway to the tissue. This result provides an explanation for the success of class-I anti-arrhythmic drugs in treating Wolff–Parkinson–White syndrome.
CAN ENDOGENOUS, NOISE-TRIGGERED EARLY AFTER-DEPOLARIZATIONS INITIATE REENTRY IN A MODIFIED LUO–RUDY VENTRICULAR VIRTUAL TISSUE?
Authors: CLAYTON R. H. , HOLDEN A. V. , TONG W. C.
Published: January 2004

EADs were produced by lowered gK,s in Luo–Rudy cell models, and could be triggered by the addition of a small noise current. Endogenous EADs, produced in a fully deterministic, or a noise driven, one-dimensional virtual tissue could initiate ectopic (unidirectional or bidirectional) propagation, and retrograde, unidirectional propagation that is the analogue of reentry in a two-dimensional tissue. Such potentially reentrant activity occurred with a low probability, for a very narrow parameter range.
REENTRY IN AN ANATOMICAL MODEL OF THE HUMAN VENTRICLES
Authors: BERNUS O. , VERSCHELDE H. , PANFILOV A. V.
Published: January 2004

We study wave propagation in a recently developed model, which reproduces geometry and fiber orientation in the right and left ventricles of the human heart. The cardiac tissue is represented using the previously developed γ-ionic model for human ventricular tissue using a spatial resolution of 0.5 mm. We simulate three-dimensional reentrant behavior resulting from a single vortex located in the free wall of the right, left ventricles and in the interventricular septum. We found that single reentrant scroll waves can generate V-shaped collision areas and in some cases, epicardial breakthrough patterns. The simulated ECGs of single spiral waves show similarities with monomorphic and polymorphic ventricular tachycardia, depending on the location of the reentrant sources. We model complex activation patterns resembling ventricular fibrillation by simulating the effects of an ATP-sensitive potassium channel opener and find that VF is, in that case, organized by a small number of vortices.
MECHANICAL INTERACTION OF HETEROGENEOUS CARDIAC MUSCLE SEGMENTSIN SILICO: EFFECTS ONCa2+HANDLING AND ACTION POTENTIAL
Authors: SOLOVYOVA O. , VIKULOVA N. , KATSNELSON L. B. , MARKHASIN V. S. , NOBLE P. J. , GARNY A. , KOHL P. , NOBLE D.
Published: January 2004

Effects of cardiac mechanical heterogeneity on the electrical function of the heart are difficult to assess experimentally, yet they pose a serious (patho-)physiological challenge. Here, we present an in silico study of the effects of mechanical heterogeneity on action potential duration (APD) in mechanically interacting muscle regions and consequent effects on the dispersion of repolarization, a well-established determinant of cardiac arrhythmogenesis.

Using a novel mathematical description of ventricular electromechanical activity (virtual muscle), we first assessed how differences in intrinsic contractile properties affect the electrical behavior of cardiac muscle representations. In spite of identical electrophysiological model descriptions in virtual muscle samples, faster muscle models show shorter APD than their slower counterparts. This is a consequence of Ca2+-mediated feedback from mechanical to electrical activity in the individual muscle models.

This mechano-electric feedback (MEF) is, of course, significantly more complex in native cardiac tissue, as the heterogeneous muscle elements interact both mechanically and electrically. Cardiac mechanical heterogeneity, in its most reduced form, can be represented by a duplex consisting of two mechanically interacting muscle segments. Our in silico model of heterogeneous myocardium therefore consists of two individual virtual muscles that are mechanically interconnected in-series to form a virtual heterogeneous duplex. During isometric contraction of the duplex (i.e. at constant external length), internal mechanical interactions affect Ca2+handling and APD of muscle elements, resulting in an increased dispersion of repolarization beyond the intrinsic APD differences.

Duplex electromechanical activity is strongly affected by the activation sequence of its elements. Late activation of the faster (subepicardial type) duplex element, postponed by time-lags that correspond to normal transmural activation delays, optimizes duplex contractility and smoothes out intrinsic APD differences, thereby reducing dispersion in repolarization. This smoothing effect is not observed upon delayed activation of the slower (subendocardial type) duplex element. In both settings, changes in repolarization timing follow a nonlinear dependence of APD on activation delay. Furthermore, asynchronous activation of identical elements in a homogeneous duplex causes an impairment of contractile function and increases dispersion of repolarization. This suggests that the normal electrical activation sequence in the heart requires matching mechanical and electrical heterogeneity for optimal cardiac performance.

On the subcellular level, our results suggest that mechanical modulation of Ca2+handling is a key mechanism of MEF in heterogeneous myocardium, which contributes to the matching of local mechanical and/or electrical activity to global hemodynamic demand.
MODELING EXCITATION AND PROPAGATION OF ACTION POTENTIALS ACROSS INHOMOGENEOUS VENTRICULAR TISSUE
Authors: LI Z. , HOLDEN A. V. , ORCHARD C. H. , ZHANG H.
Published: January 2004

Heterogeneity in the electrical activity across the ventricular wall might result from transmural differences in myocardial membrane ionic current densities. Computational models of endo- and epi-cardial action potentials of guinea-pig myocytes were developed, assuming transmural differences in the ionic current densities and kinetics of i Kr and i Ks . The cell models were able to reproduce the characteristics of action potentials of endo and epi cells. One- and two-dimensional models of ventricular tissue were also developed to study the effects of transmural heterogeneity on the propagation of excitation waves across the ventricle wall. It was shown that intercellular coupling reduces the transmural heterogeneity across the ventricle wall.
VULNERABILITY TO REENTRY, AND DRIFT, STABILITY AND BREAKDOWN OF SPIRAL WAVES IN A LINEAR GRADIENT OF GK IN A LUO–RUDY 1 VIRTUAL VENTRICULAR TISSUE
Authors: ASLANIDI O. V. , CLAYTON R. H. , HOLDEN A. V. , PHILLIPS H. K. , WARD R. J.
Published: January 2004

The vulnerable window in a heterogeneous virtual LRl cardiac tissue, with a linear gradient in GK, is wider when following propagation down the gradient, towards tissue with longer action potential duration, than when following propagation up the gradient. Spiral wave solutions in a uniform linear gradient in GK drift, with a velocity component along the gradient of the order of mm/s, towards tissue with a longer APD.
EQUILIBRIUM SELECTION IN STOCHASTIC GAMES
Authors: HERINGS P. JEAN-JACQUES , PEETERS RONALD J. A. P.
Published: January 2004

In this paper a selection theory for stochastic games is developed. The theory itself is based on the ideas of Harsanyi and Selten to select equilibria for games in standard form. We introduce several possible definitions for the stochastic tracing procedure, an extension of the linear tracing procedure to the class of stochastic games. We analyze the properties of these alternative definitions. We show that exactly one of the proposed extensions is consistent with the formulation of Harsanyi–Selten for games in standard form and captures stationarity.
THE LINEAR QUADRATIC DYNAMIC GAME FOR DISCRETE-TIME DESCRIPTOR SYSTEMS
Authors: XU HUA , MUKAIDANI HIROAKI
Published: January 2004

The linear quadratic zero-sum dynamic game for discrete time descriptor systems is considered. A method, which involves solving a linear quadratic zero-sum dynamic game for a reduced-order discrete time state space system, is developed to find the linear feedback saddle-point solutions of the problem. Checkable conditions, which are described in terms of two dual algebraic Riccati equations and a Hamiltonian matrix, are given such that the linear quadratic zero-sum dynamic game for the reduced-order discrete time state space system is available. Sufficient conditions for the existence of the solutions are obtained. In contrast with the dynamic game in state space systems, the dynamic game in descriptor systems admits uncountably many linear feedback saddle-point solutions. All these solutions have the same existence conditions and achieve the same value of the dynamic game.
HADAMARD AND TYKHONOV WELL-POSEDNESS IN TWO PLAYER GAMES
Authors: PIERI GRAZIANO , TORRE ANNA
Published: January 2004

We give a suitable definition of Hadamard well-posedness for Nash equilibria of a game, that is, the stability of Nash equilibrium point with respect to perturbations of payoff functions. Our definition generalizes the analogous notion for minimum problems. For a game with continuous payoff functions, we restrict ourselves to Hadamard well-posedness with respect to uniform convergence and compare this notion with Tykhonov well-posedness of the same game. The main results are: Hadamard implies Tykhonov well-posedness and the converse is true if the payoff functions are bounded. For a zero-sum game the two notions are equivalent.
Octreotide represses secretory-burst mass and nonpulsatile secretion but does not restore event frequency or orderly GH secretion in acromegaly
Authors: Biermasz Nienke R. , Pereira Alberto M. , Frölich Marijke , Romijn Johannes A. , Veldhuis Johannes D. , Roelfsema Ferdinand
Published: January 2004

Octreotide is a potent somatostatin analog that inhibits growth hormone (GH) release and restricts somatotrope cell growth. The long-acting octreotide formulation Sandostatin LAR is effective clinically in ∼60% of patients with acromegaly. Tumoral GH secretion in this disorder is characterized by increases in pulse amplitude and frequency, nonpulsatile (basal) release, and irregularity. Whether sustained blockade by octreotide can restore physiological secretion patterns in this setting is unknown. To address this question, we studied seven patients with GH-secreting tumors during chronic receptor agonism. Responses were monitored by sampling blood at 10-min intervals for 24 h, followed by analyses of secretion and regularity by multiparameter deconvolution and approximate entropy (ApEn). The somatostatin agonist suppressed GH secretory-burst mass, nonpulsatile (basal) GH release, and pulsatile secretion, thereby decreasing total GH secretion by 86% (range 70-96%). ApEn decreased from 1.203 ± 0.129 to 0.804 ± 0.141 ( P = 0.032), denoting greater regularity. None of GH pulse frequency, basal GH secretion rates, or ApEn normalized. In summary, chronic somatostatin agonism is able to repress amplitude-dependent measures of excessive GH secretion in acromegaly. Presumptive tumoral autonomy is inferred by continued elevations of event frequency, overall pattern disruption (irregularity), and nonsuppressible basal GH secretion.