684 research outputs found
Recommended from our members
Differential disease restriction of Moloney and Friend murine leukemia viruses by the mouse Rmcf gene is governed by the viral long terminal repeat.
Neonatal CxD2 (Rmcfr) and Balb/c (Rmcfs) mice inoculated with Moloney murine leukemia virus (M-MuLV) exhibited approximately equivalent time course and pathology for disease. CxD2 mice showed only slightly reduced presence of Moloney mink cell focus-forming virus (M-MCF) provirus as seen by Southern blot analysis compared to Balb/c mice. This lack of restriction for disease and spread of MCF was in sharp contrast to that seen for CxD2 mice inoculated with Friend murine leukemia virus (F-MuLV), where incidence of disease and propagation of MCFs were severely restricted, as previously reported. Inoculation of CxD2 mice with FM-MuLV, a recombinant F-MuLV virus containing M-MuLV LTR sequences (U3 and R), resulted in T cell disease of time course equal to that seen in Balb/c mice; there also was little restriction for propagation of MCFs. This indicated that presence of the M-MuLV long terminal repeat (LTR) was sufficient for propagation of MCFs in CxD2 mice. Differing restriction for F-MuLV vs. M-MuLV in CxD2 mice was explained on the basis of different "MCF propagator cells" for the two viruses. It was suggested that cells propagating F-MCF (e.g., erythroid progenitors) are blocked by endogenous MCF-like gp70env protein, whereas cells propagating M-MCF (e.g., lymphoid) do not express this protein on their surface. F-MuLV disease in CxD2 mice was greatly accelerated when neonates were inoculated with a F-MuLV/F-MCF pseudotypic mixture. However, F-MCF provirus was not detectable or only barely detectable in F-MuLV/F-MCF-induced tumors, suggesting that F-MCF acted indirectly in induction of these tumors
Fostering higher level comprehension abilities among fifth-grade students
The redefining of functional literacy has been advocated by recent studies of reading achievement. The National Commission on Excellence in Education, A Nation at Risk, (1983) reports the need to implement programs that will foster the development of higher thinking-language abilities. It states that these abilities are essential for meeting the challenges of an everchanging complex world. Students need to interpret, evaluate, and apply what they read. The National Assessment of Educational Progress Report (LaPointe, 1984) concurs with this view: Findings of this project reveal most students are competent in literal comprehension but lacking in higher thinking-language tasks in all areas of the curriculum
Hidden in plain sight: Cryptic and endemic malaria parasites in North American white-tailed deer (Odocoileus virginianus)
Malaria parasites of the genus Plasmodium are diverse in mammal hosts, infecting five mammalian orders in the Old World, but were long considered absent from the diverse deer family (Cervidae) and from New World mammals. There was a description of a Plasmodium parasite infecting a single splenectomized white-tailed deer (WTD; Odocoileus virginianus) in 1967 but none have been reported since, which has proven a challenge to our understanding of malaria parasite biogeography. Using both microscopy and polymerase chain reaction, we screened a large sample of native and captive ungulate species from across the United States for malaria parasites. We found a surprisingly high prevalence (up to 25%) and extremely low parasitemia of Plasmodium parasites in WTD throughout the eastern United States. We did not detect infections in the other ungulate species nor in western WTD. We also isolated the parasites from the mosquito Anopheles punctipennis. Morphologically, the parasites resemble the parasite described in 1967, Plasmodium odocoilei. Our analysis of the cytochrome b gene revealed two divergent Plasmodium clades in WTD representative of species that likely diverged 2.3 to 6 million years ago, concurrent with the arrival of the WTD ancestor into North America across Beringia. Multigene phylogenetic analysis placed these clades within the larger malaria parasite clade. We document Plasmodium parasites to be common in WTD, endemic to the New World, and as the only known malaria parasites from deer (Cervidae). These findings reshape our knowledge of the phylogeography of the malaria parasites and suggest that other mammal taxa may harbor infection by endemic and occult malaria parasites
A model checking approach to the parameter estimation of biochemical pathways
Model checking has historically been an important tool to
verify models of a wide variety of systems. Typically a model has to exhibit
certain properties to be classed ‘acceptable’. In this work we use
model checking in a new setting; parameter estimation. We characterise
the desired behaviour of a model in a temporal logic property and alter
the model to make it conform to the property (determined through
model checking). We have implemented a computational system called
MC2(GA) which pairs a model checker with a genetic algorithm. To
drive parameter estimation, the fitness of set of parameters in a model is
the inverse of the distance between its actual behaviour and the desired
behaviour. The model checker used is the simulation-based Monte Carlo
Model Checker for Probabilistic Linear-time Temporal Logic with numerical
constraints, MC2(PLTLc). Numerical constraints as well as the
overall probability of the behaviour expressed in temporal logic are used
to minimise the behavioural distance. We define the theory underlying
our parameter estimation approach in both the stochastic and continuous
worlds. We apply our approach to biochemical systems and present
an illustrative example where we estimate the kinetic rate constants in
a continuous model of a signalling pathway
The effect of different homogenization processes on the physical properties of an ice cream mixture and the resulting ice cream when the percentage of fat is varied and the solids not fat remain constant
Publication authorized February 12, 1930."The data presented in this bulletin were taken from a thesis submitted by the junior author in partial fulfillment of the requirements for the degree of Master of Arts in the Graduate School of the University of Missouri, 1928"--P. [5].Digitized 2007 AES.Includes bibliographical references (page 40)
Investigating the evolution of the dual AGN system ESO~509-IG066
We analyze the evolution of the dual AGN in ESO 509-IG066, a galaxy pair
located at z=0.034 whose nuclei are separated by 11 kpc. Previous observations
with XMM-Newton on this dual AGN found evidence for two moderately obscured
( cm) X-ray luminous ( erg/s) nuclear
sources. We present an analysis of subsequent Chandra, NuSTAR and Swift/XRT
observations that show one source has dropped in flux by a factor of 10 between
2004 and 2011, which could be explained by either an increase in the absorbing
column or an intrinsic fading of the central engine possibly due to a decrease
in mass accretion. Both of these scenarios are predicted by galaxy merger
simulations. The source which has dropped in flux is not detected by NuSTAR,
which argues against absorption, unless it is extreme. However, new Keck/LRIS
optical spectroscopy reveals a previously unreported broad H-alpha line which
is highly unlikely to be visible under the extreme absorption scenario. We
therefore conclude that the black hole in this nucleus has undergone a dramatic
drop in accretion rate. From AO-assisted near-infrared integral-field
spectroscopy of the other nucleus, we find evidence that the galaxy merger is
having a direct effect on the kinematics of the gas close to the nucleus of the
galaxy, providing a direct observational link between the galaxy merger and the
mass accretion rate on to the black hole.Comment: Accepted for publication in Ap
Broadband Observations of the Compton-thick Nucleus of NGC 3393
We present new NuSTAR and Chandra observations of NGC 3393, a galaxy reported
to host the smallest separation dual AGN resolved in the X-rays. While past
results suggested a 150 pc separation dual AGN, three times deeper Chandra
imaging, combined with adaptive optics and radio imaging suggest a single,
heavily obscured, radio-bright AGN. Using VLA and VLBA data, we find an AGN
with a two-sided jet rather than a dual AGN and that the hard X-ray, UV,
optical, NIR, and radio emission are all from a single point source with a
radius <0.2". We find that the previously reported dual AGN is most likely a
spurious detection resulting from the low number of X-ray counts (<160) at 6-7
keV and Gaussian smoothing of the data on scales much smaller than the PSF
(0.25" vs. 0.80" FWHM). We show that statistical noise in a single Chandra PSF
generates spurious dual peaks of the same separation (0.550.07" vs. 0.6")
and flux ratio (399% vs. 32% of counts) as the purported dual AGN. With
NuSTAR, we measure a Compton-thick source (NH=
cm) with a large torus half-opening angle, {\theta}=79 which we
postulate results from feedback from strong radio jets. This AGN shows a 2-10
keV intrinsic to observed flux ratio of 150. Using simulations, we find that
even the deepest Chandra observations would severely underestimate the
intrinsic luminosity of NGC 3393 above z>0.2, but would detect an unobscured
AGN of this luminosity out to high redshift (z=5).Comment: Accepted for publication in ApJ. 15 Figures and 4 table
The nature of the torus in the heavily obscured AGN Markarian 3: an X-ray study
In this paper we report the results of an X-ray monitoring campaign on the
heavily obscured Seyfert galaxy Markarian 3 carried out between the fall of
2014 and the spring of 2015 with NuSTAR, Suzaku and XMM-Newton. The hard X-ray
spectrum of Markarian 3 is variable on all the time scales probed by our
campaign, down to a few days. The observed continuum variability is due to an
intrinsically variable primary continuum seen in transmission through a large,
but still Compton-thin column density (N_H~0.8-1.110 cm).
If arranged in a spherical-toroidal geometry, the Compton scattering matter has
an opening angle ~66 degrees and is seen at a grazing angle through its upper
rim (inclination angle ~70 degrees). We report a possible occultation event
during the 2014 campaign. If the torus is constituted by a system of clouds
sharing the same column density, this event allows us to constrain their number
(175) and individual column density, [~(4.91.5)10
cm]. The comparison of IR and X-ray spectroscopic results with
state-of-the art "torus" models suggests that at least two thirds of the X-ray
obscuring gas volume might be located within the dust sublimation radius. We
report also the discovery of an ionized absorber, characterised by variable
resonant absorption lines due to He- and H-like iron. This discovery lends
support to the idea that moderate column density absorbers could be due to
clouds evaporated at the outer surface of the torus, possibly accelerated by
the radiation pressure due to the central AGN emission leaking through the
patchy absorber.Comment: Accepted for publication in MNRAS, 17 pages, 11 figures, 5 table
Building future scenarios using cognitive mapping
A participatory approach for developing future scenarios through cognitive maps as a visual representation of mental models is presented. Applying long-term future visioning techniques in a workshop setting has traditionally been a significant challenge for construction industry practitioners with a predominantly short-term, project-based approach to day-to-day operational responsibilities. Six future scenario cognitive maps are presented to illustrate the process. The maps were digitised from A1-sized papers using Decision Explorer software. Several key characteristics of the resulting cognitive maps and lessons learnt for the organisation of industry-based workshops are discussed. The main benefits are derived from the interaction between participants during the mapping process whereby future issues and their interconnectivities are discussed. Limitations of the findings and further work are presented
Computational and Mathematical Modelling of the EGF Receptor System
This chapter gives an overview of computational and mathematical modelling of the EGF receptor system. It begins with a survey of motivations for producing such models, then describes the main approaches that are taken to carrying out such modelling, viz. differential equations and individual-based modelling. Finally, a number of projects that applying modelling and simulation techniques to various aspects of the EGF receptor system are described
- …