7,043 research outputs found
Nuclease-based editing in the porcine genome : a strategy to facilitate porcine-to human xenotransplantation
Indiana University-Purdue University Indianapolis (IUPUI)Solid organ transplantation is severely limited by a shortage of available donor allografts.
Pig-to-human xenotransplantation offers a potential solution to this growing problem. For
xenotransplantation to achieve clinical relevance, both immunologic and physiologic
barriers must be understood. Genetic modification of pigs has proven to be a valuable
means of both studying and eliminating these barriers. The present body of work
describes a method for greatly increasing the efficiency and precision of genome editing
within the porcine genome. By combining non-integrating selection and homologous
recombination of exogenous oligonucleotides, a method for rapidly creating genetic
modification without reliance on phenotypic sorting was achieved. Furthermore this work
employs the technique of CRISPR/Cas9-directed mutagenesis to create and analyze
several new animal models of porcine-to-human xenotransplantation with respect to both
immunologic and physiologic parameters. First, Isoglobotrihexosylceramide -a
controversial glycan to the field of xenotransplantation- was studied in a knockout model
and found not to affect human-anti-porcine humoral reactions. Second, a new
combination of glycan modifications is described that significantly lowers the human
anti-porcine humoral immune response. This model animal suggests that glycan-deletion
alone will be sufficient to promote clinical application, and that conventional
immunosuppression will be successful in mediating the human cellular response. Finally, two potential physiologic barriers to xenotransplantation are studied in genetically
modified model animals. Xenogenic consumption of human platelets was studied across
hepatic and renal organ systems; xenogenic platelet consumption was reduced by glycan
modifications to the porcine liver while human platelet sequestration was not identified in
the study of renal endothelium. Porcine FcRN –an essential receptor expressed in
kidneys to maintain serum proteostasis- was studied as a final potential barrier to pig-to
human renal transplantation. Because albumin is the primary driver of serum oncotic
pressure, the protein-protein interaction of endogenous porcine FcRN and human
albumin was studied. Porcine FcRN was found capable of binding human albumin under
physiologic parameters. In summary, the results of the present work suggest that the
salient barriers to clinical xenotransplantation have been removed and that porcine-to
human renal transplantation may soon offer an answer to the current organ shortage
Deriving Iodine-free spectra for high-resolution echelle spectrographs
We describe a new method to derive clean, iodine-free spectra directly from
observations acquired using high-resolution echelle spectrographs equipped with
iodine cells. The main motivation to obtain iodine-free spectra is to use
portions of the spectrum that are superimposed with the dense forest of iodine
absorption lines, in order to retrieve lines that can be used to monitor the
magnetic activity of the star, helping to validate candidate planets. In short,
we provide a straight-forward methodology to clean the spectra by using the
forward model used to derive radial velocities, the Line Spread Function
information plus the stellar spectrum without iodine to reconstruct and
subtract the iodine spectrum from the observations. We show our results using
observations of the star Ceti acquired with the PFS, HIRES and UCLES
spectrographs, reaching an iodine-free spectrum correction at the 1% RMS
level. We additionally discuss the limitations and further applications of the
method.Comment: 15 pages, 7 figures. Accepted for publication in A
Quenched Chiral Perturbation Theory for Baryons
We develop quenched chiral perturbation theory for baryons using the
graded-symmetry formalism of Bernard and Golterman and calculate non-analytic
contributions to the baryon masses coming from quenched chiral loops. The usual
term proportional to is substantially altered due to the
cancellation of diagrams with internal quark loops. In addition, the
``hairpin'' vertex leads to a new correction, proportional to . We
compare our results to numerical lattice data and use them to estimate the size
of the quenching error in the octet baryon masses.Comment: 7 pages (An abridged version of this note will appear in the
proceedings of Lattice'93. Latex + 14 postscript files, bundled using
uufiles. Needs psfig.) UW/PT-93-0
Less government intervention in biodiversity management: risks and opportunities
n a changing global environment, with increasing pressure on ecosystem goods and services, biodiversity conservation is likely to become increasingly important. However, with the current global financial crisis, governments are increasingly trying to stabilise economies through spending cuts aiming to reduce national deficits. Within such an economic climate, the devolution of governance through public participation is an intrinsically appealing concept. We outline a number of challenges that explain why increased participation in biodiversity management has been and may continue to be problematic. Using as a case study the local stakeholder-driven Moray Firth Seal Management Plan in Scotland, we identify four key conditions that were crucial to the successful participatory management of a biodiversity conflict: a local champion, the emergence of a crisis point, the involvement of decision-makers, and long-term financial and institutional support. Three of the four conditions point to the role of direct government involvement, highlighting the risk of devolving responsibility for biodiversity conflict management to local communities. We argue that without an informed debate, the move towards a more participatory approach could pose a danger to hard-won policy gains in relation to public participation, biodiversity conservation and conflict management
Crossing the Brown Dwarf Desert Using Adaptive Optics: A Very Close L-Dwarf Companion to the Nearby Solar Analog HR 7672
We have found a very faint companion to the active solar analog HR 7672 (HD
190406; GJ 779; 15 Sge). Three epochs of high resolution imaging using adaptive
optics (AO) at the Gemini-North and Keck II Telescopes demonstrate that HR
7672B is a common proper motion companion, with a separation of 0.79" (14 AU)
and a 2.16 um flux ratio of 8.6 mags. Using follow-up K-band spectroscopy from
Keck AO+NIRSPEC, we measure a spectral type of L4.5+/-1.5. This is the closest
ultracool companion around a main sequence star found to date by direct
imaging. We estimate the primary has an age of 1-3 Gyr. Assuming coevality, the
companion is most likely substellar, with a mass of 55-78 Mjup based on
theoretical models. The primary star shows a long-term radial velocity trend,
and we combine the radial velocity data and AO imaging to set a firm
(model-independent) lower limit of 48 Mjup. In contrast to the paucity of brown
dwarf companions at <~4 AU around FGK dwarfs, HR 7672B implies that brown dwarf
companions do exist at separations comparable to those of the giant planets in
our own solar system. Its presence is at variance with scenarios where brown
dwarfs form as ejected stellar embryos. Moreover, since HR 7672B is likely too
massive to have formed in a circumstellar disk as planets are believed to, its
discovery suggests that a diversity of physical processes act to populate the
outer regions of exoplanetary systems.Comment: Astrophysical Journal, in pres
Aerobrake assembly with minimum Space Station accommodation
The minimum Space Station Freedom accommodations required for initial assembly, repair, and refurbishment of the Lunar aerobrake were investigated. Baseline Space Station Freedom support services were assumed, as well as reasonable earth-to-orbit possibilities. A set of three aerobrake configurations representative of the major themes in aerobraking were developed. Structural assembly concepts, along with on-orbit assembly and refurbishment scenarios were created. The scenarios were exercised to identify required Space Station Freedom accommodations. Finally, important areas for follow-on study were also identified
Metal-ligand interplay in strongly-correlated oxides: a parametrized phase diagram for pressure induced spin transitions
We investigate the magnetic properties of archetypal transition-metal oxides
MnO, FeO, CoO and NiO under very high pressure by x-ray emission spectroscopy
at the K\beta line. We observe a strong modification of the magnetism in the
megabar range in all the samples except NiO. The results are analyzed within a
multiplet approach including charge-transfer effects. The pressure dependence
of the emission line is well accounted for by changes of the ligand field
acting on the d electrons and allows us to extract parameters like local
d-hybridization strength, O-2p bandwidth and ionic crystal field across the
magnetic transition. This approach allows a first-hand insight into the
mechanism of the pressure induced spin transition.Comment: 5 pages, 3 figure
The Long Road to Developing Native Herbaceous Summer Forage Legume Ecotypes
Only a handful of well-adapted herbaceous summer forage legumes are currently marketed for drier regions of North America and even fewer are true natives. There is a growing demand for native germplasm in the region as a new generation of landowner attempts to return grasslands to a semblance of their original species and diversity. The objective of this paper is to describe preliminary research results of a grasslands team collecting, studying and promulgating native leguminous germplasm in Texas
Inequalities in bariatric surgery in Australia: findings from 49,364 obese participants in a prospective cohort study
OBJECTIVES: To investigate variation, and quantify socioeconomic inequalities, in receipt of primary bariatric surgery in an obese population. DESIGN, SETTING AND PARTICIPANTS: Prospective population-based cohort study of 49,364 individuals aged 45-74 with body mass index (BMI) ≥30kg/m2, with questionnaire (2006-09) linked to hospital and death data to July 2010. Sample drawn from the 45 and Up Study (~10% of NSW population aged ≥45 included, response rate ~18%). MAIN OUTCOME MEASURES: Rates of bariatric surgery and adjusted rate ratios (RR) in relation to health and sociodemographic characteristics. RESULTS: Over 111,757 person-years (py) of follow-up, 312 participants underwent bariatric surgery, a rate of 27.92/10,000 py (95%CI: 24.91-31.19). Rates were highest in women, people living in major cities and those with diabetes, and increased significantly with increasing body-mass-index and number of chronic health conditions. Adjusted RRs were: 5.27 (3.18-8.73) for annual household-income ≥20,000; and 4.01 (2.41-6.67) for those living in areas in the least- versus most-disadvantaged quintile. Private health insurance (PHI) coverage (age-sex adjusted RR: 9.25; 5.70-15.00) partially explained the observed socioeconomic inequalities. CONCLUSIONS: Bariatric surgery has been shown to be cost-effective in treating severe obesity and associated illnesses. While bariatric surgery rates in Australia are higher in those with health problems, large socioeconomic inequalities are apparent. Our findings suggest these procedures are largely available to those who can afford PHI and associated out-of-pocket costs, with poor access in populations who are most in need. Continuing inequalities in access are likely to exacerbate existing inequalities in obesity and related health problems.National Health and Medical Research Council (NHMRC
Dynamic interpretation of slug tests in highly permeable aquifers
This is the published version. Copyright American Geophysical Union[1] Considerable progress has been made in developing a theoretical framework for modeling slug test responses in formations with high hydraulic conductivity K. However, several questions of practical significance remain unresolved. Given the rapid and often oscillatory nature of test responses, the traditional hydrostatic relationship between the water level and the transducer-measured head in the water column may not be appropriate. A general dynamic interpretation is proposed that describes the relationship between water level response and transducer-measured head. This theory is utilized to develop a procedure for transforming model-generated water level responses to transducer readings. The magnitude of the difference between the actual water level position and the apparent position based on the transducer measurement is a function of the acceleration and velocity of the water column, test geometry, and depth of the transducer. The dynamic approach explains the entire slug test response, including the often-noted discrepancy between the actual initial water level displacement and that measured by a transducer in the water column. Failure to use this approach can lead to a significant underestimation of K when the transducer is a considerable distance below the static water level. Previous investigators have noted a dependence of test responses on the magnitude of the initial water level displacement and have developed various approximate methods for analyzing such data. These methods are re-examined and their limitations clarified. Practical field guidelines are proposed on the basis of findings of this work. The soundness of the dynamic approach is demonstrated through a comparison of K profiles from a series of multilevel slug tests with those from dipole-flow tests performed in the same wells
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