We examine deep Chandra X-ray observations of the Centaurus cluster of galaxies, Abell 3526. Applying a gradient magnitude filter reveals a wealth of structure, from filamentary soft emission on ...100 pc (0.5 arcsec) scales close to the nucleus to features 10 s of kpc in size at larger radii. The cluster contains multiple high-metallicity regions with sharp edges. Relative to an azimuthal average, the deviations of metallicity and surface brightness are correlated, and the temperature is inversely correlated, as expected if the larger scale asymmetries in the cluster are dominated by sloshing motions. Around the western cold front are a series of ∼7 kpc ‘notches’, suggestive of Kelvin–Helmholtz instabilities. The cold front width varies from 4 kpc down to close to the electron mean free path. Inside the front are multiple metallicity blobs on scales of 5–10 kpc, which could have been uplifted by AGN activity, also explaining the central metallicity drop and flat inner metallicity profile. Close to the nucleus are multiple shocks, including a 1.9-kpc-radius inner shell-like structure and a weak 1.1–1.4 Mach number shock around the central cavities. Within a 10 kpc radius are nine depressions in surface brightness, several of which appear to be associated with radio emission. The shocks and cavities imply that the nucleus has been repeatedly active on 5–10 Myr time-scales, indicating a tight balance between heating and cooling. We confirm the presence of a series of linear quasi-periodic structures. If they are sound waves, the ∼5 kpc spacing implies a period of 6 Myr, similar to the ages of the shocks and cavities. Alternatively, these structures may be Kelvin–Helmholtz instabilities, their associated turbulence or amplified magnetic field layers.
We present a detailed Chandra, XMM-Newton, Very Large Array (VLA) and Hubble Space Telescope analysis of one of the strongest cool core clusters known, RX J1532.9+3021 (z = 0.3613). Using new, deep ...90 ks Chandra observations, we confirm the presence of a western X-ray cavity or bubble, and report on a newly discovered eastern X-ray cavity. Based on the distribution of the optical filaments, as well as a jet-like structure seen in the 325 MHz VLA radio map, we suggest that the cluster harbors older outflows along the north to south direction. The jet of the central AGN is therefore either precessing or sloshing-induced motions have caused the outflows to change directions. We confirm that the central AGN is highly sub-Eddington and conclude that a > 10 super(10) M sub(middot in circle) or a rapidly spinning black hole is favored to explain both the radiative-inefficiency of the AGN and the powerful X-ray cavities.
The most controversial fishery in U.S. waters of the Gulf of Mexico (Gulf) is for northern red snapper Lutjanus campechanus, which collapsed in the late 1980s when stock biomass became too low to be ...fished commercially in the eastern Gulf. Red snapper management began in 1989; the stock is now showing signs of recovery. The Gulf of Mexico Fishery Management Council has been slow to sufficiently reduce catches of the directed fisheries to rebuild the stock in a timely fashion, although compliance with the Magnuson-Stevens Reauthorization Act of 2006 (MSRA) required substantial cuts in the harvest of red snapper beginning in 2007. In our opinion, this could have been avoided if conservative management practices had been adopted earlier. We believe that ‘faith-based fisheries' arguments have been used to defer effective management of red snapper in the Gulf, which in turn has strained the relationship between science, management, and stakeholders there. We provide a simple empirical argument and alternate interpretations of a recently published perspective on the historical fishery of red snapper in the Gulf to conclude that the preponderance of evidence used in the agency stock assessment process, and the simple arguments made here, do not support the perspective that the red snapper stock has increased in size sufficiently to defer compliance with the MSRA.
A major goal of bone tissue engineering is to design better scaffold configuration and materials to better control osteoblast behavior. Nanoporous architecture has been shown to significantly affect ...cellular response. In this work, nanoporous alumina membranes were fabricated by a two-step anodization method to investigate bone cell response. Osteoblasts were seeded on nanoporous alumina membranes to investigate both short-term adhesion and proliferation and long-term functionality and matrix production. Cell adhesion and proliferation were characterized using a standard MTT assay and cell counting. The total protein content was measured after cell lysis using the BCA assay. Matrix production was characterized in terms of surface concentrations of calcium and phosphorous, components of bone matrix, using X-ray photoelectron spectroscopy (XPS). The results from nanoporous alumina membranes were compared with those of amorphous alumina, aluminum, commercially available ANOPORE
TM and glass. Results indicate improved osteoblast adhesion and proliferation and increased matrix production after 4 weeks of study.
Abstract Bacterial infection is one of the most common problems after orthopedic implant surgery. If not prevented, bacterial infection can result in serious and life threatening conditions such as ...osteomyelitis. Thus, in order to reduce chances of such serious complication, patients are often subjected to antibiotic drug therapy for 6–8 weeks after initial surgery. The antibiotics are systemically delivered either intravenously, intramuscularly or topically. Systemic antibiotic delivery entails certain drawbacks such as systemic toxicity and limited bioavailability. Further, in order for the drug to be effective at the site of implantation, high doses are required, which can result in undesired side effects in patients. Thus, local antibiotic therapy is the preferred way of administering drugs. To that end, we have developed titania nanotubular arrays for local delivery of antibiotics off-implant at the site of implantation. These nanotubes were fabricated on bulk titanium using anodization techniques. The fabrication strategies allow us to precisely control the nanotube length and diameter, thus enabling us to load different amounts of drugs and control the release rates. In this work we have fabricated titania nanotubes with 80 nm diameter and 400 nm length. We have loaded these tubes with 200, 400 and 600 μg of gentamicin. The gentamicin release kinetics from these nanotubes and its effect on Staphylococcus epidermis adhesion were investigated. Further, a preosteoblastic cell line called MC3T3-E1 was cultured on gentamicin-loaded nanotubes to evaluate the effect of nanoarchitecture on cell functionality. Our results indicate that we can effectively fill the nanotubes with the drug and the drug eluting nanotubes significantly reduce bacterial adhesion on the surface. Also, there is enhanced osteoblast differentiation on nanotubes filled with gentamicin.
Abstract A goal of current orthopedic biomaterials research is to design implants that induce controlled, guided, and rapid healing. In addition to acceleration of normal wound healing phenomena, ...these implants should result in the formation of a characteristic interfacial layer with adequate biomechanical properties. To achieve these goals, however, a better understanding of events at the bone–material interface is needed, as well as the development of new materials and approaches that promote osseointegration. Using anodization, titania interfaces can be fabricated with controlled nanoarchitecture. This study demonstrates the ability of these surfaces to promote osteoblast differentiation and matrix production, and enhance short- and long-term osseointegration in vitro . Titania nanotubular surfaces were fabricated using an anodization technique. Marrow stromal cells (MSCs) were isolated from male Lewis rats and seeded on these surfaces along with control surfaces. The interaction of cells with these surfaces was investigated in terms of their ability to adhere, proliferate and differentiate on them. The experiments were repeated three times with cells from different cultures. All the results were analyzed using analysis of variance (ANOVA). Statistical significance was considered at p <0.05. Furthermore, in vivo biocompatibility was assessed by implanting surfaces subcutaneously in male Lewis rat and performing histological analysis after 4 weeks. Our results indicate that the nanotubular titania surfaces provide a favorable template for the growth and maintainence of bone cells. The cells cultured on nanotubular surfaces showed higher adhesion, proliferation, ALP activity and bone matrix deposition compared to those grown on flat titanium surfaces. In vivo biocompatibility results suggest that nanotubular titania does not cause chronic inflammation or fibrosis. The fabrication routes of titania nano-architectures are flexible and cost-effective, enabling realization of desired platform topologies on existing non-planar orthopedic implants.
Abstract Cellular immunoisolation using semi-permeable barriers has been investigated over the past several decades as a promising treatment approach for diseases such as Parkinson's, Alzheimer's, ...and Type 1 diabetes. Typically, polymeric membranes are used for immunoisolation applications; however, recent advances in technology have led to the development of more robust membranes that are able to more completely meet the requirements for a successful immunoisolation device, including well controlled pore size, chemical and mechanical stability, nonbiodegradability, and biocompatibility with both the graft tissue as well as the host. It has been shown previously that nanoporous alumina biocapsules can act effectively as immunoisolation devices, and support the viability and functionality of encapsulated β cells. The aim of this investigation was to assess the biocompatibility of the material with host tissue. The cytotoxicity of the capsule, as well as its ability to activate complement and inflammation was studied. Further, the effects of poly(ethylene glycol) (PEG) modification on the tissue response to implanted capsules were studied. Our results have shown that the device is nontoxic and does not induce significant complement activation. Further, in vivo work has demonstrated that implantation of these capsules into the peritoneal cavity of rats induces a transient inflammatory response, and that PEG is useful in minimizing the host response to the material.
Mounting evidence suggests that some populations of benthic marine organisms may be less demographically 'open' than previously thought. The degree to which a population receives recruits from local ...sources versus other populations has important ecological and management ramifications.
For either of these reasons, it is often desirable to estimate the degree to which a population of interest is self-recruiting. Although methods for actual estimation of population self-recruitment are limited and often difficult to employ, the presence of several biological and physical conditions
may improve our estimates of self-recruitment for particular populations. Biological traits of benthic adults (relative fecundity, spatial and temporal patterns of spawning and larval release, parental investment), as well as pelagic larvae (stage of development at hatching, pelagic larval
duration, vertical migration behavior, horizontal swimming ability, and sensory capabilities) influence where and when larvae are released, where and how they are transported, their ability to move actively in the pelagic realm, and finally, spatial and temporal settlement patterns. Physical
variables potentially influencing self-recruitment include site isolation, coastal complexity and flow variability. Within these physical variables we discuss explicit mechanisms by which larvae may be retained in proximity to their natal population. We provide examples from specific locations
such as coral reefs, isolated islands and seamounts, and semi-enclosed embayments such as lagoons and estuaries, as well as characteristic oceanographic features such as upwelling systems, fronts, moving convergences, eddies and counter currents. We evaluate direct and indirect evidence to
predict the relationship between these biophysical variables and the degree of self-recruitment in benthic marine organisms. We conclude that physical factors that result in a departure from unidirectional, depth-uniform water flow provide the opportunity for retention of larvae, and therefore
of self-recruitment. These physical factors are common in the ocean and vary in intensity among locations and times. Some enable retention of passive larvae (physical retention), whereas others lead to retention only with active behavioral input by the larvae (biophysical retention). Larval
behavior that can contribute to or result in retention or return to natal sites ranges from simple vertical orientation (within the capabilities of the larvae of most taxa) to complex sensory abilities and strong swimming (known to occur in larvae of a few taxa, particularly decapod crustaceans
and fishes). For all taxa, both the pelagic larval duration and the time to behavioral competency will have a strong influence on likelihood of self-recruitment. Understanding the biophysical mechanisms by which larvae are retained near or return to their natal population will be necessary
before generalizations can be made. Examples highlight the importance of each variable to processes controlling self-recruitment. For most correlates, further study is clearly warranted. Although certain variables hold promise for predicting self-recruitment, complex, non-linear interactions
among these biophysical variables must be considered.
Satellite-based rainfall monitoring is widely used for climatological studies because of its full global coverage but it is also of great importance for operational purposes especially in areas such ...as Africa where there is a lack of ground-based rainfall data. Satellite rainfall estimates have enormous potential benefits as input to hydrological and agricultural models because of their real time availability, low cost and full spatial coverage. One issue that needs to be addressed is the uncertainty on these estimates. This is particularly important in assessing the likely errors on the output from non-linear models (rainfall-runoff or crop yield) which make use of the rainfall estimates, aggregated over an area, as input. Correct assessment of the uncertainty on the rainfall is non-trivial as it must take account of
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the difference in spatial support of the satellite information and independent data used for calibration
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uncertainties on the independent calibration data
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the non-Gaussian distribution of rainfall amount
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the spatial intermittency of rainfall
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the spatial correlation of the rainfall field
This paper describes a method for estimating the uncertainty on satellite-based rainfall values taking account of these factors. The method involves firstly a stochastic calibration which completely describes the probability of rainfall occurrence and the pdf of rainfall amount for a given satellite value, and secondly the generation of ensemble of rainfall fields based on the stochastic calibration but with the correct spatial correlation structure within each ensemble member. This is achieved by the use of geostatistical sequential simulation. The ensemble generated in this way may be used to estimate uncertainty at larger spatial scales. A case study of daily rainfall monitoring in the Gambia, west Africa for the purpose of crop yield forecasting is presented to illustrate the method.
Titanium thin films, 400 nm to 1000 nm thick, fabricated by radio frequency (rf) sputter deposition are anodized in an electrolyte containing acetic acid and hydrofluoric acid to form optically ...transparent films of highly ordered titania nanotube arrays. Real‐time monitoring of the anodization current, at a fixed potential, is used to controllably eliminate the Ti layer underneath the titanium oxide nanotube array without disturbing the architecture. Fabrication variables critical to achieving the transparent nanotube‐array film include annealing temperature of the anodized, initially amorphous nanotube array and Ti‐film sputter deposition variables, including rate, film thickness, and substrate temperature. Structural investigations on the transparent nanotube arrays reveal only the presence of the anatase phase even after annealing at 500 °C. In contrast, both rutile and anatase phases were observed in films with a metal layer underneath the nanotubes and annealed in an oxygen ambient above 430 °C. Rutile growth occurs at the nanotube–metal interface as metal oxidation takes place during annealing. The average refractive index of the transparent nanotube‐array film is found to be 1.66 in the UV‐vis range, with a calculated porosity of 67 %; the bandgap is determined as 3.34 eV, with a bandgap tail extending to 2.4 eV.
Highly ordered titania nanotube arrays (see Figure) that are transparent to visible light can be produced by anodizing, in a fluoride‐containing electrolyte, a radio frequency‐sputtered titanium thin film. The arrays show excellent hydrogen‐gas‐sensing and water‐photoelectrolysis properties and could find active use in photovoltaic and antireflection coating applications.
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