3,772 research outputs found
Substitutability between Equity REITs and Mortgage REITs
This study extends Seck’s (1996) approach to investigate the degree of substitutability between equity real estate investment trusts (EREITs) and mortgage real estate investment trusts (MREITs). The variance ratio test and the variance decomposition of forecast errors yield results indicating the existence of informational commonality between EREITs and MREITs. The findings indicate that the two types of REITs are substitutable. A direct implication is that investors who believe they have superior forecasting ability will be indifferent to invest in either type of REIT. Another implication is that REITs can be treated as a single asset class in constructing a diversified multi-asset portfolio.
Plasma membrane association by N-acylation governs PKG function in Toxoplasma gondii
ABSTRACT
Cyclic GMP (cGMP)-dependent protein kinase (protein kinase G [PKG]) is essential for microneme secretion, motility, invasion, and egress in apicomplexan parasites, However, the separate roles of two isoforms of the kinase that are expressed by some apicomplexans remain uncertain. Despite having identical regulatory and catalytic domains, PKG
I
is plasma membrane associated whereas PKG
II
is cytosolic in
Toxoplasma gondii
. To determine whether these isoforms are functionally distinct or redundant, we developed an auxin-inducible degron (AID) tagging system for conditional protein depletion in
T. gondii
. By combining AID regulation with genome editing strategies, we determined that PKG
I
is necessary and fully sufficient for PKG-dependent cellular processes. Conversely, PKG
II
is functionally insufficient and dispensable in the presence of PKG
I
. The difference in functionality mapped to the first 15 residues of PKG
I
, containing a myristoylated Gly residue at position 2 that is critical for membrane association and PKG function. Collectively, we have identified a novel requirement for cGMP signaling at the plasma membrane and developed a new system for examining essential proteins in
T. gondii
.
IMPORTANCE
Toxoplasma gondii
is an obligate intracellular apicomplexan parasite and important clinical and veterinary pathogen that causes toxoplasmosis. Since apicomplexans can only propagate within host cells, efficient invasion is critically important for their life cycles. Previous studies using chemical genetics demonstrated that cyclic GMP signaling through protein kinase G (PKG)-controlled invasion by apicomplexan parasites. However, these studies did not resolve functional differences between two compartmentalized isoforms of the kinase. Here we developed a conditional protein regulation tool to interrogate PKG isoforms in
T. gondii
. We found that the cytosolic PKG isoform was largely insufficient and dispensable. In contrast, the plasma membrane-associated isoform was necessary and fully sufficient for PKG function. Our studies identify the plasma membrane as a key location for PKG activity and provide a broadly applicable system for examining essential proteins in
T. gondii
.
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Supercongruences and Complex Multiplication
We study congruences involving truncated hypergeometric series of the
form_rF_{r-1}(1/2,...,1/2;1,...,1;\lambda)_{(mp^s-1)/2} =
\sum_{k=0}^{(mp^s-1)/2} ((1/2)_k/k!)^r \lambda^k where p is a prime and m, s, r
are positive integers. These truncated hypergeometric series are related to the
arithmetic of a family of algebraic varieties and exhibit Atkin and
Swinnerton-Dyer type congruences. In particular, when r=3, they are related to
K3 surfaces. For special values of \lambda, with s=1 and r=3, our congruences
are stronger than what can be predicted by the theory of formal groups because
of the presence of elliptic curves with complex multiplications. They
generalize a conjecture made by Rodriguez-Villegas for the \lambda=1 case and
confirm some other supercongruence conjectures at special values of \lambda.Comment: 19 page
The mechanics of network polymers with thermally reversible linkages.
Abstract Not Provide
Levee Flood Hazard Scenario Analysis Application
The development of a GIS Application based on ArcGIS version 9.2 was determined to fulfill the requirements of the Federal Emergency Management Agency for calculating the impacts of different flood hazard scenarios using the flood hazard data available to them with other publicly available data such as census data. The application was designed and implemented to be used by non-geographic information system professionals to use the tools and perform the necessary analyses required to formulate the needed results. The implemented application is made up of a file geodatabase to store the data, a toolset to help define the flood hazard polygons for a specific flood scenario, and models to perform routine analyses of the scenarios to determine some of the impacts on a community. Impacts such as population impacted, housing units impacted, and miles of levee in an area were implemented using models in ArcMap. This application will show the potential power of the geospatial flood hazard data that FEMA is producing as part of their Map Modernization efforts and showcase its use in a geographic information system
Tracking Jesusa: Geographic Information Systems and Character Development in Hasta no verte, Jesús mío
This study examines the uses of mapping software and web tools to produce multimedia annotations of a literary work—in this case Hasta no verte, Jesús mío by Elena Poniatowska—to the end of strengthening student engagement with the text, and cultural and literary contexts. The authors, a professor and a student at Auburn University-Montgomery, photographed scenes of specific sites and landmarks mentioned in the novel, mapped them on Google Maps, then linked the sites with historic photos of the periods indicated in the novel, in preparation for creating a unique website
CASE STUDY: International Association of Machinists and Boeing Joint Quality Through Training Programs
The International Association of Machinists (IAM) and Boeing
Company Quality Through Training Program (QTTP) is playing a
vital role within the Boeing Company to cope with a complicated
situation: reducing the workforce, implementing lean
manufacturing, and the upcoming training of a new workforce as
thousands of workers prepare for retirement in the coming years.
QTTP Joint Training Programs were not created with these
specific uses in mind, but because the programs are already
established, they provide a foundation on which to build these new
roles. Internal union and management groups are now relying on
the credibility and connections of the QTTP leadership to facilitate
organizational problem-solving. This case study describes how the
joint program has responded to new organizational needs
heightened by sudden changes in the aerospace industry.
The events of September 11, 2001 were devastating for the
aerospace industry. One year after the tragic events, (you say
below that airlines postponed or cancelled orders) business air
travel had declined approximately 30% while air travel overall was
off approximately 11%. The airline industry was projected to lose
more than 7.7 billion in 2001.
United Airlines filed for bankruptcy, while most other airlines
continue to post stunning losses. In response to the drop in air
travel demand, the airlines reduced the number of flights –
requiring less aircraft. As a result, airlines postponed or cancelled
orders for new planes. Boeing’s commercial business was hit hard
and the company has announced the layoff of 30,000 workers.
Despite this rather bleak picture, the QTTP leaders and
representatives continue to skillfully promote joint, innovative
activities that are mutually beneficial to those they represent. The
activities described in this case are examples of the initiatives that
QTTP is promoting. Of note is the consideration and respect that form the basis upon which decisions are made within the group
CASE STUDY: Rockwell Collins and IBEW Locals 1362 and 1634
The post-September 11th economy has confronted Rockwell Collins in Cedar
Rapids, Iowa with hard choices. Faced with the need to cut costs, including
laying off significant portions of the work force, the company and its unions
still maintain a commitment to knowledge
retention and knowledge building. This case
study chronicles the efforts of this leading
producer of advanced communication and
aviation electronics for the commercial market
and the defense industry to balance the costs of
maintaining productive effectiveness while
responding to market pressures. The company is
faced with increased technical requirements and
depressed demand for its products, which
include: in-flight entertainment systems, aircraft
communication systems, global positioning
systems (GPS), flight deck displays (including collision alert systems and
virtual landing aids), communications systems, and automatic flight controls.
Survival depends on walking a strategic knife edge to sustain the bottom line
and still maintain the innovation and flexibility needed to build products to
market demand
Finding Variable Stars in Planetary Nebulae Using the ISIS Image Subtraction Software
Planetary nebulae are a brief and often spectacular stage in the life of stars like the sun during which the star expels its outer layers into space. In order to explain the great variety of observed shapes among planetary nebulae, we are examining the theory that binary central stars of planetary nebulae are a significant factor in their shaping. We determine if the central star of planetary nebulae is binary by looking for photometric periodic variability, a common feature of close binary systems. Using existing data we evaluate the variability using a computer program called ISIS. We have seen the central star of Pe 1-9 show variability due to a close binary system. The remaining analyzed targets Mz 2, NGC 5844, NGC 2392 show no variability within our detection limits, and the results from NGC2899 were inconclusive
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