On the mechanical stability of growing arteries

Arteries are modeled, within the framework of nonlinear elasticity, as incompressible two-layer cylindrical structures that are residually stressed through differential growth. These structures are loaded by an axial force, internal pressure and have nonlinear, anisotropic, hyperelastic response to stresses. Parameters for this model are directly related to experimental observations. The possible role of axial residual stress in regulating stress in arteries and preventing buckling instabilities is investigated. It is shown that axial residual stress lowers the critical internal pressure leading to buckling and that a reduction of axial loading may lead to a buckling instability which may eventually lead to arterial tortuosity

Elastic cavitation, tube hollowing, and differential growth in plants and biological tissues

Elastic cavitation is a well-known physical process by which elastic materials under stress can open cavities. Usually, cavitation is induced by applied loads on the elastic body. However, growing materials may generate stresses in the absence of applied loads and could induce cavity opening. Here, we demonstrate the possibility of spontaneous growth-induced cavitation in elastic materials and consider the implications of this phenomenon to biological tissues and in particular to the problem of schizogenous aerenchyma formation

WIDESPREAD BLOCKS OF GENOMIC HYPOMETHYLATION IN HUMAN AGING AND SUN EXPOSURE

Human aging is the greatest risk factor for disease and mortality, however the molecular mechanisms are poorly understood. The process involves altered cellular function but occurs without predictable genetic change and is variable among individuals, indicating that epigenetic change may be involved. DNA methylation is an epigenetic mark with important roles in regulating gene expression and cellular identity. Widespread differences in DNA methylation have been observed in cancer, EBV transformation of lymphocytes and replicative senescence. Early work considering epigenetic change in aging identified global changes in methylation highly variable among individuals. Recent work has identified specific genomic regions in which DNA methylation consistently changes with age, however the genome scale patterns and the factors underlying this change remain unclear. In this work, we use genome wide methods to clarify the nature of age related epigenetic change. Using human skin samples, we identify widespread genomic blocks of hypomethylation in chronically sun-exposed epidermis but not sun-protected, aged tissue, implicating environmental stress in mediating large-scale epigenetic change. The degree of hypomethylation in the identified blocks correlates with clinical measures of photo- aging and the identified blocks are further hypomethylated in squamous cell carcinoma samples compared to matched controls. In another study, using purified monocytes and lymphocytes from human peripheral blood, we observe highly cell type specific patterns of methylation change with age. In lymphocytes, we observe widespread blocks of hypomethylation similar to the changes identified in cancer and chronically sun-exposed epidermis, while in monocytes, no large-scale change is present with age. In addition, we identify smaller regions differentially methylated with age in each cell type that occur in cell type specific enhancers and contain motifs for regulatory factor binding, indicating methylation change with age may be linked to the regulation of cell identity. Given the widespread blocks of hypomethylation observed in skin and blood systems, we investigate the link between block methylation and proliferation by using whole genome bisulfite sequencing to measure DNA methylation in growth arrested and actively dividing primary fibroblasts. We demonstrate that methylation in block regions is stable over replication and through extended arrest

An inline optical electron polarimeter

The design and operation of a simple inline optical electron polarimeter is presented. It is based on exchange excitation of ground state neon atoms. The electron polarization is determined from the degree of circular polarization of the subsequent 2p53p 3D3→2p53s 3P2 (6402 Å) fluorescence. This device can characterize both longitudinally and transversely polarized electron beams in a nondestructive fashion, and is inexpensive and easily constructed

Feasibility and initial efficacy of project-based treatment for people with ABI

Background: Communication impairments are common and pervasive for people a long time following acquired brain injury (ABI). These impairments have a significant impact on a person's quality of life (QOL) post‐injury. Project‐based treatment is a treatment approach that could have an impact on communication skills and QOL for people with ABI a long‐term post‐injury. This treatment is embedded in a context of meaningful activities chosen by people with ABI, whereby, as a group, they work collaboratively to achieve a tangible end product. Aims: To evaluate the feasibility and initial efficacy of project‐based treatment on improving the communication skills and QOL for people with ABI. Methods & Procedures: An exploratory controlled trial with alternate allocation of groups, and follow‐up at 6–8 weeks, was completed. Twenty‐one people with chronic ABI were recruited in groups of two to three from community settings, allocated to either a TREATMENT (n = 11) or WAITLIST group (n = 10). Participants attended a 20‐h group‐based treatment over 6 weeks where they worked towards achieving a project that helped others. To determine feasibility, four criteria were used: demand, implementation, practicality and acceptability. A range of communication and QOL outcomes was used to determine a fifth feasibility criterion, initial efficacy. Some of these criteria were additionally used to evaluate the feasibility of the outcomes. Outcomes & Results: All participants received the treatment as allocated with high attendance and no dropouts. The treatment was feasible to deliver as intended and was highly acceptable to participants. Medium and large effect sizes were found from pre‐ to post‐treatment, and from pre‐treatment to follow‐up for measures of conversation, perceived communicative ability and QOL. Conclusions & Implications: Project‐based treatment is feasible with indications of initial efficacy for both communication skills and QOL. The treatment provides a promising new approach for improving communication skills and QOL in people with chronic acquired brain injuries in the community setting

Support for Integrated Ecosystem Assessments of NOAA’s National Estuarine Research Reserves System (NERRS), Volume I: The Impacts of Coastal Development on the Ecology and Human Well-being of Tidal Creek Ecosystems of the US Southeast

A study was conducted, in association with the Sapelo Island and North Carolina National Estuarine Research Reserves (NERRs), to evaluate the impacts of coastal development on sentinel habitats (e.g., tidal creek ecosystems), including potential impacts to human health and well-being. Uplands associated with southeastern tidal creeks and the salt marshes they drain are popular locations for building homes, resorts, and recreational facilities because of the high quality of life and mild climate associated with these environments. Tidal creeks form part of the estuarine ecosystem characterized by high biological productivity, great ecological value, complex environmental gradients, and numerous interconnected processes. This research combined a watershed-level study integrating ecological, public health and human dimension attributes with watershed-level land use data. The approach used for this research was based upon a comparative watershed and ecosystem approach that sampled tidal creek networks draining developed watersheds (e.g., suburban, urban, and industrial) as well as undeveloped sites. The primary objective of this work was to clearly define the relationships between coastal development with its concomitant land use changes and non-point source pollution loading and the ecological and human health and well-being status of tidal creek ecosystems. Nineteen tidal creek systems, located along the southeastern United States coast from southern North Carolina to southern Georgia, were sampled during summer (June-August), 2005 and 2006. Within each system, creeks were divided into two primary segments based upon tidal zoning: intertidal (i.e., shallow, narrow headwater sections) and subtidal (i.e., deeper and wider sections), and watersheds were delineated for each segment. In total, we report findings on 24 intertidal and 19 subtidal creeks. Indicators sampled throughout each creek included water quality (e.g., dissolved oxygen concentration, salinity, nutrients, chlorophyll-a levels), sediment quality (e.g., characteristics, contaminants levels including emerging contaminants), pathogen and viral indicators, and abundance and genetic responses of biological resources (e.g., macrobenthic and nektonic communities, shellfish tissue contaminants, oyster microarray responses). For many indicators, the intertidally-dominated or headwater portions of tidal creeks were found to respond differently than the subtidally-dominated or larger and deeper portions of tidal creeks. Study results indicate that the integrity and productivity of headwater tidal creeks were impaired by land use changes and associated non-point source pollution, suggesting these habitats are valuable early warning sentinels of ensuing ecological impacts and potential public health threats. For these headwater creeks, this research has assisted the validation of a previously developed conceptual model for the southeastern US region. This conceptual model identified adverse changes that generally occurred in the physical and chemical environment (e.g., water quality indicators such as indicator bacteria for sewage pollution or sediment chemical contamination) when impervious cover levels in the watershed reach 10-20%. Ecological characteristics responded and were generally impaired when impervious cover levels exceed 20-30%. Estimates of impervious cover levels defining where human uses are impaired are currently being determined, but it appears that shellfish bed closures and the flooding vulnerability of headwater regions become a concern when impervious cover values exceed 10-30%. This information can be used to forecast the impacts of changing land use patterns on tidal creek environmental quality as well as associated human health and well-being. In addition, this study applied tools and technologies that are adaptable, transferable, and repeatable among the high quality NERRS sites as comparable reference entities to other nearby developed coastal watersheds. The findings herein will be of value in addressing local, regional and national needs for understanding multiple stressor (anthropogenic and human impacts) effects upon estuarine ecosystems and response trends in ecosystem condition with changing coastal impacts (i.e., development, climate change). (PDF contaions 88 pages

Using Model Test Data to Assess VIV Factor of Safety for SCR and TTR in GOM

This paper presents results obtained as part of the DeepStar Phase 10 program on VIV Factors of Safety. The objective was to develop a general methodology to calibrate Factors of Safety for VIV-induced fatigue and to apply it to partially straked risers. This was achieved using reliability methods, accepted industry VIV prediction software and state-of-the-art model test experiments. Most oil companies use a Factor of Safety of 20 when predicting VIV damage using VIV software tools. There are numerous software tools currently in use in industry to predict VIV damage to straked risers and each of them will have different accuracy, and therefore an intrinsic level of conservatism. Understanding the level of conservatism in different VIV prediction software is therefore critical to determining what Factor of Safety to use. This study benchmarks the latest generation of industry accepted VIV design tools at the time of the study (2011): SHEAR7v4.6, VIVAv6.5 and VIVANAv3.7.24 against high quality VIV data from three separate straked riser experiments. A bias distribution (predicted to measured VIV damage results) is obtained for each software tool as a function of the strake coverage. A novel reliability framework approach is then developed to incorporate all uncertainties associated with VIV fatigue prediction into a limit state function, including variability in met-ocean conditions and variability in the fatigue resistance of the material characterized by a design S-N curve. The limit state function is analyzed using First Order Reliability Methods to develop Factors of Safety for target probabilities of failure. The general method is then applied on two case studies involving an SCR and TTR in Gulf of Mexico loop currents, but it can be easily extended to different locations and riser configurations. The resulting FoS range from about 1 to 15 for most software, and are lower than industry standards for VIV prediction. The FoS do not vary markedly for different riser configurations, indicating the possibility of reducing excess conservatism when predicting VIV damage on straked risers.DeepStar (Consortium)SHEAR7 JI