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We studied the osteoconductive tissue response of hydroxyapatite (HA) nanoparticles functionalized with osteopontin (OPN) in a matrix of poly- D,L-lactic-acid (PDLLA). In a canine endosseus 0.75-mm gap implant model, we tested the osteointegrative impact of the OPN functionalized composite as an implant coating, and a non-functionalized composite was used as reference control. During the four weeks of observation, the OPN functionalized composite coating significantly increased the formation of new bone in the porosities of the implant, but no differences were observed in the gap. The study provides evidence of its potential use either alone or in combination with other osteoconductive compounds. © 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 99A: 94-101, 2011. [ABSTRACT FROM AUTHOR]

The crack procedure is a surgical technique for preparing the implant cavity at revision of loose joint replacement components. It disrupts the neocortical bone shell that typically forms around the cavity. Using an animal model, we compared the crack technique with reaming. Twenty micromotion implants were inserted bilaterally into the knees of 10 dogs according to our revision protocol, allowing formation of a standardized revision cavity (loose implant, fibrous tissue, and sclerotic bone rim). Eight weeks later we performed revision surgery. On the control side, in which the neocortex was removed, the cavity was reamed. On the intervention side, in which the neocortex was perforated but left in situ, the cavity was cracked. For revision we used non-motioning hydroxyapatite (HA)-coated, plasma-sprayed titanium implants. Observation after revision was 4 weeks. The implants revised by the crack technique had better mechanical fixation in all mechanical parameters by the push-out test. The crack revisions also provided more new bone formation around the implants compared with the reamed revisions but had no effect on new bone ongrowth. The data suggest using this bone-sparing technique may be superior to reaming in terms of achieving improved early implant fixation of uncemented HA-coated revision implants. [ABSTRACT FROM AUTHOR]

We announce the discovery of a new Milky Way satellite Segue 2 found in the data of the Sloan Extension for Galactic Understanding and Exploration (SEGUE). We followed this up with deeper imaging and spectroscopy on the Multiple Mirror Telescope (MMT). From this, we derive a luminosity of , a half-light radius of 34 pc and a systemic velocity of . Our data also provide evidence for a stream around Segue 2 at a similar heliocentric velocity, and the SEGUE data show that it is also present in neighbouring fields. We resolve the velocity dispersion of Segue 2 as 3.4 km s−1 and the possible stream as . This object shows points of comparison with other recent discoveries, Segue 1, Boo II and Coma. We speculate that all four objects may be representatives of a population of satellites of satellites – survivors of accretion events that destroyed their larger but less dense parents. They are likely to have formed at redshifts and are good candidates for fossils of the reionization epoch. [ABSTRACT FROM AUTHOR]

We introduced an 15N-NH4+ tracer to the riparian forest of a salmon-bearing stream (Kennedy Creek, Washington, USA) to quantify the cycling and fate of a late-season pulse of salmon N and, ultimately, mechanisms regulating potential links between salmon abundance and tree growth. The 15N tracer simulated deposition of 7.25 kg of salmon (fresh) to four 50-m² plots. We added NH4+ (the initial product of salmon carcass decay) and other important nutrients provided by carcasses (P, S, K, Mg, Ca) to soils in late October 2003, coincident with local salmon spawning. We followed the 15N tracer through soil and tree pools for one year. Biological uptake of the 15N tracer occurred quickly: 64% of the 15N tracer was bound in soil microbiota within 14 days, and roots of the dominant riparian tree, western red cedar (Thuja plicata), began to take up 15N tracer within seven days. Root uptake continued through, the winter. The 15N tracer content of soil organic matter reached a maximum of ∼52%, five weeks after the application, and a relative equilibrium of ∼40% within five months. Six months after the addition, in spring 2004, at least 37% of the 15N tracer was found in tree tissues: ∼23% in foliage, ∼11% in roots, and ∼3% in stems. Within the stems, xylem and phloem sap contained ∼96% of the tracer N, and ∼4% was in structural xylem N. After one year, at least 28% of the 15N tracer was still found in trees, and loss from the plots was only ∼20%. The large portion of tracer N taken up in the fall and reallocated to leaves and stems the following spring provides mechanistic evidence for a one-year-lagged tree-growth response to salmon nutrients. Salmon nutrients have been deposited in the Kennedy Creek system each fall for centuries, but the system shows no evidence of nutrient saturation. Rates of N uptake and retention are a function of site history and disturbance and also may be the result of a legacy effect, in which annual salmon nutrient addition may lead to increased efficiency of nutrient uptake and use. [ABSTRACT FROM AUTHOR]

1. River valleys resemble dynamic mosaics, composed of patches which are natural, transient features of the land surface produced by the joint action of a river and successional processes over years to centuries. They simultaneously regulate and reflect the distribution of stream energy and exchanges of sediment, wood and particulate organic matter between riparian and aquatic environments. 2. We determined the structure, composition, dynamics and origin of seven patch types at the reach scale in the Queets River valley in the temperate coastal forests of the Olympic Mountains, Washington (U.S.A.). Patch types included: (1) primary and (2) secondary channels; (3) pioneer bars; (4) developing and (5) established floodplains; and (6) transitional and (7) mature fluvial terraces. 3. Lateral channel movements strongly shape patch distribution, structure and dynamics. The primary channel moved laterally 13 m year−1, on average from 1939 to 2002, but was highly variable among locations and over time. Mean lateral movement rates ranged from 1 to 59 m year−1 and moving averages (2 km) ranged from 3 to 28 m year−1 throughout the valley. 4. Each patch type exhibited characteristic vegetation, soil and accumulations of large wood. Pioneer bars contained peak stem density (69 778 stems ha−1) and volume of large wood (289 m3 ha−1). Mature fluvial terraces contained the highest mean stem (1739 m3 ha−1) and canopy volume (158 587 m3 ha−1). These patches also contained the most soil nitrogen (537 kg ha−1) and carbon (5972 kg ha−1). 5. Patch half-life (the time required for half of the existing patches to be eroded) ranged from 21 to 401 years among forested patch types. Erosion rates were highest in pioneer bars (2.3% year−1) and developing floodplains (3.3% year−1), compared with only 0.17% year−1 in mature fluvial terraces. New forests formed continually, as pioneering vegetation colonised 50% of the channel system within 18 years, often unsuccessfully. 6. In the Queets River, the structure, composition, and dynamics of the patchy riparian forest depends on the interplay between channel movements and biophysical feedbacks between large wood, living vegetation and geomorphic processes. The cycle of patch development perpetuates a shifting-mosaic of habitats within the river valley capable of supporting diverse biotic assemblages. [ABSTRACT FROM AUTHOR]

The structure and extinction of diffusion flames generated by a porous spherical burner or a fuel droplet in response to rotational motion were investigated through perturbation analysis, with emphasis on the effects of non-unity Lewis numbers ( Le ) for both fuel and oxidizer. The analysis shows that the rotational motion induces a secondary flow that distorts the otherwise spherical flame into a pancake shape. The flame temperature is also affected, such that the flame becomes more susceptible to extinction either at the poles or the equator, depending on the combined effects of Lewis numbers, flame stretch through local flow non-uniformity and ambient oxidizer concentration. The results reported here will help guide planned microgravity experiments. [ABSTRACT FROM AUTHOR]

The counterflow diffusion flame subject to time-varying strain rates is studied analytically in order to assess the effect that unsteadiness caused by turbulent flows might have on laminar flamelets. The characteristic unsteady time considered is of the same order as the characteristic flame time, which is represented by the reciprocal of the strain rate, such that the flame structure consists of a quasi-steady reactive-diffusive zone embedded within the outer unsteady-convective-diffusive region. For constant density and unity Lewis numbers, the Shvab-Zeldovich coupling function takes an analytic self-similar solution for arbitrary strain rate as a function of time, thereby facilitating the analysis as well as physical interpretation for the flame-sheet behaviors. We further analyze the inner reaction zone structure using large activation energy asymptotics for one-step overall chemistry in order to determine the extinction conditions. In relation to turbulent combustion regimes, the unsteady effect is expected to modify the flamelet behavior subject to the spectrum of turbulent eddies. That is, although the effective strain rate increases as the eddy scale is decreased, the smaller eddies also have shorter characteristic time such that the flame may not be quenched for some range of eddy scale that otherwise imparts sufficient strain rate to extinguish the flamelet. The results suggest that the applicable range of the laminar flamelet regime may be broader than would be expected from the quasi-steady concept. [ABSTRACT FROM PUBLISHER]

The article presents a study on the development of a theoretical model that investigates the interaction between endothelial cells and osteoblastic population into a gap healing model of orthopaedic implants. It states that reactive transport equations were used in predicting the spatio-temporal distribution patterns of neoformed tissue because of osteoblast activity in connection with endothelial cell morphogenes and population. Results show less significance in the post-operative gap.

We analyze the structure of laminar diffusion flames at high pressure in the limit of large activation energy for the particular configuration of a steady flame in counterflow. We consider a dense fluid in which normal Fickian diffusion of the fuel is limited, and thermal diffusion, i.e., the Soret effect, is the dominant mechanism for fuel mass transport. Temperature and species profiles, as well as flame temperature and location, are determined as a function of Damköhler number and Soret diffusion coefficient. In particular, we find that oxidant is entirely consumed by the flame, while some fuel leaks through. For light fuels, the fuel profile is found to have a local peak on the oxidant side as a result of thermal diffusion. Our analysis includes a description of extinction phenomena, including explicit criteria in terms of the Soret diffusion coefficient, ratio of temperature of the two streams, and the Damköhler number at extinction. [ABSTRACT FROM AUTHOR]