The Pseudosynchronization of Binary Stars Undergoing Strong Tidal Interactions

Eccentric binaries known as heartbeat stars experience strong dynamical tides as the stars pass through periastron, providing a laboratory to study tidal interactions. We measure the rotation periods of 24 heartbeat systems, using the Kepler light curves to identify rotation peaks in the Fourier transform. Where possible, we compare the rotation period to the pseudosynchronization period derived by Hut 1981. Few of our heartbeat stars are pseudosynchronized with the orbital period. For four systems, we were able to identify two sets of rotation peaks, which we interpret as the rotation from both stars in the binary. The majority of the systems have a rotation period that is approximately 3/2 times the pseudosynchronization period predicted by Hut 1981, suggesting that other physical mechanisms influence the stars' rotation, or that stars typically reach tidal spin equilibrium at a rotation period slightly longer than predicted.Comment: 9 pages, 4 figures, 1 table

Time valued life cycle greenhouse gas emissions from buildings

The UK has adopted legally binding carbon reduction targets of 34% by 2020 and 80% by 2050 (measured against the 1990 baseline). Buildings are estimated to be responsible for more than 50% of greenhouse gas (GHG) emissions in the UK. These consist of both operational, produced during use, and embodied, produced during manufacture of materials and components, and during construction, refurbishments and demolition. A brief assessment suggests that it is unlikely that UK emission reduction targets can be met without substantial reductions in both Oc and Ec. Oc occurs over the lifetime of a building whereas the bulk of Ec occurs at the start of a building’s life. A time value for emissions could influence the decision making process when it comes to comparing mitigation measures which have benefits that occur at different times. An example might be the choice between building construction using low Ec construction materials versus building construction using high Ec construction materials but with lower Oc, although the use of high Ec materials does not necessarily imply a lower Oc. Particular time related issues examined here are: the urgency of the need to achieve large emissions reductions during the next 10 to 20 years; the earlier effective action is taken, the less costly it will be; future reduction in carbon intensity of energy supply; the carbon cycle and relationship between the release of GHG’s and their subsequent concentrations in the atmosphere. An equation is proposed, which weights emissions according to when they occur during the building life cycle, and which effectively increases Ec as a proportion of the total, suggesting that reducing Ec is likely to be more beneficial, in terms of climate change, for most new buildings. Thus, giving higher priority to Ec reductions is likely to result in a bigger positive impact on climate change and mitigation costs

Stimulation of osteoblasts using rest periods during bioreactor culture on collagen-glycosaminoglycan scaffolds.

Osteoblasts respond to mechanical signals which play a key role in the formation of bone however, after extended periods of stimulation they become desensitised. Mechanosensitivity has been shown to be restored by the introduction of resting periods between loadings. The aim of this study was to analyse the effect of rest periods on the response of osteoblast-like cells seeded on collagen-glycosaminoglycan (CG) scaffolds in a flow perfusion bioreactor up to 14 days. Short (10 s) and long (7 h) term rests were incorporated into stimulation patterns. Constructs cultured in the bioreactor had a more homogenous cell distribution albeit with lower cell numbers than the static group. Osteopontin expression was significantly higher on the rest-inserted group than on the steady flow and static control. These results indicate that the insertion of short term rests during flow improves cellular distribution and osteogenic responses on CG constructs cultured in a flow perfusion bioreactor

Challenges for Requirements Development: An Industry Perspective

It is well recognised that software requirements must accurately reflect the needs of a target domain, however, challenges still exist in effectively acheiving this. This paper reports on the results of an industry-based study investigating factors that affect the communication of requirements between the development team and other stakeholders during requirements development. Challenges found in practice are related to common obstacles reported in the literature. The paper concludes with a discussion of the findings including implications for Software Process Improvement (SPI) in requirements developmen

Coupling Freshly Isolated CD44(+) Infrapatellar Fat Pad-Derived Stromal Cells with a TGF-β3 Eluting Cartilage ECM-Derived Scaffold as a Single-Stage Strategy for Promoting Chondrogenesis.

An alternative strategy to the use of in vitro expanded cells in regenerative medicine is the use of freshly isolated stromal cells, where a bioactive scaffold is used to provide an environment conducive to proliferation and tissue-specific differentiation in vivo. The objective of this study is to develop a cartilage extracellular matrix (ECM)-derived scaffold that could facilitate the rapid proliferation and chondrogenic differentiation of freshly isolated stromal cells. By freeze-drying cryomilled cartilage ECM of differing concentrations, it is possible to produce scaffolds with a range of pore sizes. The migration, proliferation, and chondrogenic differentiation of infrapatellar fat pad-derived stem cells (FPSCs) depend on the concentration/porosity of these scaffolds, with greater sulphated glycosaminoglycan (sGAG) accumulation observed in scaffolds with larger-sized pores. It is then sought to determine if freshly isolated fat pad-derived stromal cells, seeded onto a transforming growth factor (TGF)-β3 eluting ECM-derived scaffold, could promote chondrogenesis in vivo. While a more cartilage-like tissue could be generated using culture expanded FPSCs compared to nonenriched freshly isolated cells, fresh CD44(+) stromal cells are capable of producing a tissue in vivo that stained strongly for sGAGs and type II collagen. These findings open up new possibilities for in-theatre cell-based therapies for joint regeneration

Dynamic compression can inhibit chondrogenesis of mesenchymal stem cells.

The objective of this study was to investigate the influence of dynamic compressive loading on chondrogenesis of mesenchymal stem cells (MSCs) in the presence of TGF-beta3. Isolated porcine MSCs were suspended in 2% agarose and subjected to intermittent dynamic compression (10% strain) for a period of 42 days in a dynamic compression bioreactor. After 42 days in culture, the free-swelling specimens exhibited more intense alcian blue staining for proteoglycans, while immunohistochemical analysis revealed increased collagen type II immunoreactivity. Glycosaminoglycan (GAG) content increased with time for both free-swelling and dynamically loaded constructs, and by day 42 it was significantly higher in both the core (2.5+/-0.21%w/w vs. 0.94+/-0.03%w/w) and annulus (1.09+/-0.09%w/w vs. 0.59+/-0.08%w/w) of free-swelling constructs compared to dynamically loaded constructs. This result suggests that further optimization is required in controlling the biomechanical and/or the biochemical environment if such stimuli are to have beneficial effects in generating functional cartilaginous tissue

A Class of Eccentric Binaries with Dynamic Tidal Distortions Discovered with Kepler

We have discovered a class of eccentric binary systems within the Kepler data archive that have dynamic tidal distortions and tidally-induced pulsations. Each has a uniquely shaped light curve that is characterized by periodic brightening or variability at time scales of 4-20 days, frequently accompanied by shorter period oscillations. We can explain the dominant features of the entire class with orbitally-varying tidal forces that occur in close, eccentric binary systems. The large variety of light curve shapes arises from viewing systems at different angles. This hypothesis is supported by spectroscopic radial velocity measurements for five systems, each showing evidence of being in an eccentric binary system. Prior to the discovery of these 17 new systems, only four stars, where KOI-54 is the best example, were known to have evidence of these dynamic tides and tidally-induced oscillations. We perform preliminary fits to the light curves and radial velocity data, present the overall properties of this class and discuss the work required to accurately model these systems.Comment: 13 pages, submitted to Ap

Infrapatellar Fat Pad Stem Cells: From Developmental Biology to Cell Therapy

The ideal cell type to be used for cartilage therapy should possess a proven chondrogenic capacity, not cause donor-site morbidity, and should be readily expandable in culture without losing their phenotype. There are several cell sources being investigated to promote cartilage regeneration: mature articular chondrocytes, chondrocyte progenitors, and various stem cells. Most recently, stem cells isolated from joint tissue, such as chondrogenic stem/progenitors from cartilage itself, synovial fluid, synovial membrane, and infrapatellar fat pad (IFP) have gained great attention due to their increased chondrogenic capacity over the bone marrow and subcutaneous adipose-derived stem cells. In this review, we first describe the IFP anatomy and compare and contrast it with other adipose tissues, with a particular focus on the embryological and developmental aspects of the tissue. We then discuss the recent advances in IFP stem cells for regenerative medicine. We compare their properties with other stem cell types and discuss an ontogeny relationship with other joint cells and their role on in vivo cartilage repair. We conclude with a perspective for future clinical trials using IFP stem cells

Solubility of carbon dioxide in renneted casein matrices: effect of pH, salt, temperature, partial pressure, and moisture to protein ratio

The solubility of carbon dioxide (CO2) in the moisture and protein components of cheese matrices and the influence of changing pH, salt and temperature levels remains unclear. In this study, model casein matrices were prepared, by renneting of micellar casein concentrate (MCC), with modulation of salt and pH levels by adding salt and glucono delta-lactone, respectively, to the MCC solutions prior to renneting. Different moisture-to-protein levels were achieved by freeze-drying, incubation of samples at different relative humidities, or by applying varying pressures during gel manufacture. The CO2 solubility of samples decreased linearly with both increasing temperature and salt-in-moisture content, whereas solubility of CO2 increased with increasing pH. A non-linear relationship was observed between CO2 solubility and the moisture-to-protein ratio of experimental samples. Overall, such knowledge may be applied to improve the quality and consistency of eye-type cheese, and in particular to avoid development of undesirable slits and cracks