Modeling the onset and propagation of trabecular bone microdamage during low-cycle fatigue

Relatively small amounts of microdamage have been suggested to have a major effect on the mechanical properties of bone. A significant reduction in mechanical properties (e.g. modulus) can occur even before the appearance of microcracks. This study uses a novel non-linear microdamaging finite-element (FE) algorithm to simulate the low-cycle fatigue behavior of high-density trabecular bone. We aimed to investigate if diffuse microdamage accumulation and concomitant modulus reduction, without the need for complete trabecular strut fracture, may be an underlining mechanism for low-cycle fatigue failure (defined as a 30% reduction in apparent modulus). A microCT constructed FE model was subjected to a single cycle monotonic compression test, and constant and variable amplitude loading scenarios to study the initiation and accumulation of low-cycle fatigue microdamage. Microcrack initiation was simulated using four damage criteria: 30%, 40%, 50% and 60% reduction in bone element modulus (el-MR). Evaluation of structural (apparent) damage using the four different tissue level damage criteria resulted in specimen fatigue failure at 72, 316, 969 and 1518 cycles for the 30%, 40%, 50% and 60% el-MR models, respectively. Simulations based on the 50% el-MR model were consistent with previously published experimental findings. A strong, significant non-linear, power law relationship was found between cycles to failure (N) and effective strain (Deltasigma/E(0)): N=1.394x10(-25)(Deltasigma/E(0))(-12.17), r(2)=0.97, p<0.0001. The results suggest that microdamage and microcrack propagation, without the need for complete trabecular strut fracture, are mechanisms for high-density trabecular bone failure. Furthermore, the model is consistent with previous numerical fatigue simulations indicating that microdamage to a small number of trabeculae results in relatively large specimen modulus reductions and rapid failure.     

Multi-purpose HealthCare Telemedicine Systems with mobile communication link support

The provision of effective emergency telemedicine and home monitoring solutions are the major fields of interest discussed in this study. Ambulances, Rural Health Centers (RHC) or other remote health location such as Ships navigating in wide seas are common examples of possible emergency sites, while critical care telemetry and telemedicine home follow-ups are important issues of telemonitoring. In order to support the above different growing application fields we created a combined real-time and store and forward facility that consists of a base unit and a telemedicine (mobile) unit. This integrated system: can be used when handling emergency cases in ambulances, RHC or ships by using a mobile telemedicine unit at the emergency site and a base unit at the hospital-expert's site, enhances intensive health care provision by giving a mobile base unit to the ICU doctor while the telemedicine unit remains at the ICU patient site and enables home telemonitoring, by installing the telemedicine unit at the patient's home while the base unit remains at the physician's office or hospital. The system allows the transmission of vital biosignals (3–12 lead ECG, SPO2, NIBP, IBP, Temp) and still images of the patient. The transmission is performed through GSM mobile telecommunication network, through satellite links (where GSM is not available) or through Plain Old Telephony Systems (POTS) where available. Using this device a specialist doctor can telematically "move" to the patient's site and instruct unspecialized personnel when handling an emergency or telemonitoring case. Due to the need of storing and archiving of all data interchanged during the telemedicine sessions, we have equipped the consultation site with a multimedia database able to store and manage the data collected by the system. The performance of the system has been technically tested over several telecommunication means; in addition the system has been clinically validated in three different countries using a standardized medical protocol.     

The concept of life and its significance in the construction of the new ecosystem ecology of Bernard Patten, Sven Jørgensen and Milan Straskraba

In a series of articles, three system ecologists, B. Patten, S. J?rgensen and M. Straskraba attempt to construct a new ecosystem ecology. In this effort, an innovative ecological definition of life that originates from the cognitive domain is prevalent. To be more specific, living entities are defined as those who make models of reality. Through the exploration of this definition, we will try to point out the ontological and the epistemological characteristics of the new ecology. These characteristics facilitate the integration of physicochemical, biological and human systems into a common framework. Indeed, system ecologists attempt to unify the inorganic and the organic world, including human beings, under a universal evolutionary scheme. This scheme is organized around an innovative scientific hypothesi, namely the exergy storage hypothesis.     

Autecology of an intertidal Alaskan harpacticoid copepod Apolethon sp.

The life history and ecology of a harpacticoid copepod, Apolethon sp., were investigated for one year in the intertidal zone of a subarctic bay in southeastern Alaska. Core samples were collected biweekly at the 0 m tidal level from March, 1992 through March, 1993; zonation and vertical distribution were determined from additional samples. Large seasonal variations in density of Apolethon sp. parallelled that of the total harpacticoid community, with highest densities (124.3±12.5 10 cm^–2; mean ± standard error) in March and lowest densities in May and October (7.6±4.5). The sex ratio of Apolethon sp. varied directly with population density, varying from <0.1 to 1.2 (male:female) during the study period. The species was restricted to a relatively narrow vertical band within the intertidal zone, having its greatest density at – 1 m and being rare above + 1 m tidal height. Adult Apolethon sp. bear conspicuous ovoid mucin structures located laterally on the genital double-somite. The mucin structures are unique to the species; several putative functions are discussed.     

Phenotypic plasticity or speciation? A case from a clonal marine organism

Background  

Clonal marine organisms exhibit high levels of morphological variation. Morphological differences may be a response to environmental factors but also they can be attributed to accumulated genetic differences due to disruption of gene flow among populations. In this study, we examined the extensive morphological variation (of 14 characters) in natural populations observed in the gorgonian Eunicea flexuosa, a widely distributed Caribbean octocoral. Eco-phenotypic and genetic effects were evaluated by reciprocal transplants of colonies inhabiting opposite ends of the depth gradient and analysis of population genetics of mitochondrial and nuclear genes, respectively.     

Population genetic patterns of the copepod Calanus sinicus in the northwest Pacific

Mixing zones between aquatic ecosystems are known diversity hot spots, but so far no study evaluated the effect of mixing waters on bacterial metabolism. Samplings were performed in four of the major Amazonian rivers, and aquatic bacterial production (BP) was measured both before the confluences and in the mixing zones downstream of the confluences. BP in mixing zones was higher than before the confluence in 75% of cases, representing an increase ranging from 31% to more than 1,000% of BP. In most of these cases, the confluence zone was formed by aquatic ecosystems that differed in the water type (environmental conditions and limiting nutrients to BP). The proportional contribution of the water from each source in the mixture had no impact on the outcome of BP in the mixtures, while BP in the mixtures peaked after 12 h of mixing, indicating that the increase in BP can continue downstream from the confluence zone. Overall, the results presented here do not contradict the low aquatic bacterial metabolism suggested for most Amazonian waters, but show that this general pattern may be sprinkled with hot spot areas of high bacterial metabolism in the confluence of aquatic ecosystems.     

A new species of Litarachna (Acari,Hydrachnidia, Pontarachnidae) from a Caribbean mesophotic coral ecosystem

New records of pontarachnid mites (Acari: Hydrachnidia) from the Caribbean island of Puerto Rico are presented. Litarachna lopezae sp. n., from substrata collected from Bajo de Sico, a mesophotic coral reef ecosystem in Mona Passage off Puerto Rico, is described as new to science. The new species was collected from nearly 70 m depth, the greatest depth from which pontarachnid mites have been found until now. In addition, a Litarachna sp. was also found in association with the tube of the polychaete Sabellastarte magnifica (Shaw, 1800) at the shallow waters of north Puerto Rico.     

Isolation and genotyping of novel T4 cyanophages associated with diverse coral reef invertebrates

Coral Reefs - In an effort to facilitate virus isolation-based studies on coral reefs, we describe here a simple holobiont virus extraction protocol that is effective at separating and...     

Quantification of new structural features of coronary plaques by computational post-hoc analysis of virtual histology-intravascular ultrasound images

Cardiovascular disease and complications are often mediated by the development and rupture of atherosclerotic plaques. Plaque composition is a major factor that determines plaque vulnerability. Intravascular ultrasound (IVUS) and spectral analysis of the radio frequency signal provide an in vivo tissue characterisation of atherosclerotic plaques, known as virtual histology (VH–IVUS). In VH–IVUS analysis, four histological tissue components are classified: fibrous, fibro/fatty, necrotic core and calcium. Existing technology determines only the area of each component within the plaque. Quantitative, objective characterisation of other plaque components' patterns within the plaque is lacking. The aim of this study was to determine new compositional and structural indices which indicate spatial distribution, heterogeneity and dispersity of each VH–IVUS-derived component within the plaque area and also with respect to the plaque–lumen border. We developed an automated computational system in Java for the analysis of both single cross-sectional segments and the whole length of the examined plaque (volumetric analysis). The following parameters were computed: the number of different solid segments and the area of the largest solid segment of each component within the plaque, the per cent of the lumen border that is surrounded by each component, the number of different solid segments and the largest area of a solid segment of each component that adjoins the lumen border. Especially components' localisation in relation to the lumen border may significantly influence plaque vulnerability and plaque–stent interaction, which should be investigated in future clinical studies.