912 research outputs found
Economies of Scale for Real Estate Investment Trusts
Using the translog cost function to estimate economies of scale for a sample of Real Estate Investment Trusts for the years 1992-1994, we find significant evidence that economies of scale exist for REITs for all years examined. The results show that measurement of scale economies is sensitive to the model used for the measurement. Individual characteristics of the REIT, such as type of management and degree of leverage, affect the magnitude of the scale economy. Additional variables accounting for property type diversification and geographic influences have little additional impact on the measured scale economies. Finally, the measured economies of scale for REITs vary considerably over time.
Maintenance of Residential Rental Property: An Empirical Analysis
The maintenance costs of 137 residential rental properties in northwestern South Carolina are analyzed. The results show that maintenance cost per square foot increases with property age, tenant turnover, certain amenities, and for higher-rent properties. Compared to other property types, apartments exhibit higher maintenance costs per square foot with larger complexes showing lower per square foot maintenance costs than smaller complexes. This cost economy suggests added value to rental housing for larger complexes. Owners of multiple properties are found to pay higher maintenance costs. Finally, there is no observed relationship between absentee ownership and the level of property maintenance.
Reexamining the Impact of Employee Relocation Assistance on Housing Prices
In this paper, we reexamine the issue of whether corporate relocation assistance programs for transferred employees significantly affect sale prices of single-family homes. We estimate a hedonic price equation that includes physical housing characteristics, location factors, occupancy status, and type of seller for a sample of 2,441 transactions. Seller types include (a) transferred employees who were given direct relocation assistance, (b) transferred employees who were not given direct relocation assistance, and (c) sellers who were not facing an employment transfer. After controlling for vacancy and tenant occupancy, we find that houses sold by transferred employees who receive direct relocation assistance exhibit no significant price differential, but that houses sold by transferred employees who do not receive direct relocation assistance sell at a discount of approximately 3%.
Radiative Decays X(3872) -> psi(2S)+gamma and psi(4040) -> X(3872)+gamma in Effective Field Theory
Heavy hadron chiral perturbation theory (HHchiPT) and XEFT are applied to the
decays X(3872) -> psi(2S) + gamma and psi(4040) -> X(3872) + gamma under the
assumption that the X(3872) is a molecular bound state of neutral charm mesons.
In these decays the emitted photon energies are 181 MeV and 165 MeV,
respectively, so HHchiPT can be used to calculate the underlying D^0
bar{D}^{0*}+ bar{D}^0 D^{0*} -> psi(2S) + gamma or psi(4040) -> (D^0
bar{D}^{0*}+ bar{D}^0 D^{0*}) + gamma transition. These amplitudes are matched
onto XEFT to obtain decay rates. The decays receive contributions from both
long distance and short distance processes. We study the polarization of the
psi(2S) in the decay X(3872) -> psi(2S) + gamma and the angular distribution of
X(3872) in the decay psi(4040) -> X(3872) + gamma and find they can be used to
differentiate between different decay mechanisms as well as discriminate
between 2^{-+} and 1^{++} quantum number assignments of the X(3872).Comment: 13 pages, 4 figure
Particle and particle pair dispersion in turbulence modeled with spatially and temporally correlated stochastic processes
In this paper we present a new model for modeling the diffusion and relative
dispersion of particles in homogeneous isotropic turbulence. We use an
Heisenberg-like Hamiltonian to incorporate spatial correlations between fluid
particles, which are modeled by stochastic processes correlated in time. We are
able to reproduce the ballistic regime in the mean squared displacement of
single particles and the transition to a normal diffusion regime for long
times. For the dispersion of particle pairs we find a -dependence of the
mean squared separation at short times and a -dependence for long ones. For
intermediate times indications for a Richardson law are observed in
certain situations. Finally the influence of inertia of real particles on the
dispersion is investigated.Comment: 10 pages, 7 figures, 1 tabl
Increased overwinter mortalities of white-tailed deer (Odocoileus virginianus) fawns during a drought year
Mortality rates of white-tailed deer (Odocoileus virginianus (Zimmerman, 1780)) fawns have been quantified throughout North America. Few studies, however, have assessed cause-specific mortality of fawns after the first 3 months of life or during a severe weather event. During 2010-2014, we captured and radiotracked 93 fawns in southern and central Illinois and recorded 18 mortality events. In order of importance, survival rates were affected by days since capture, year of drought, age at capture, week post-capture (1/0 indicator), and region. Estimated overwinter (fall through spring) survival rate (± SE) of fawns in both regions during 2010-14 was 0.83 ± 0.04. However, estimated overwinter survival rates were depressed during 2012-13, following the severe drought of 2012 (0.63 ± 0.11 or 0.66 ± 0.11 depending on model). Main causes of mortality were capture-related and predation, though some dead deer also showed signs of hemorrhagic disease. We suspect that the extreme drought of 2012 created favorable conditions for fall-spring mortality of fawns, due to elevated disease transmission and lower forage quality and quantity for deer. In addition, drought may have contributed to predation by reducing abundance of alternative prey. Our results suggest that severe weather conditions during summer can substantially impact overwinter fawn survival
Evapotranspiration of two vegetation communities in a high-elevation riparian meadow at Hart Prairie, Arizona
Hart Prairie, Arizona, has the largest Bebb willow (Salix bebbiana) community in the United States; however, greater than 95% of willows are older than 80 years and regeneration by seed is not occurring. This study examined the evapotranspiration of two herbaceous communities that dominate the Hart Prairie watershed: (1) a mixture of bracken fern (Pteridium aquilinum) and graminoids and (2) dominantly graminoids. Transpiration during premonsoon and postmonsoon dry periods of 2000, 2001, and 2002 was estimated for each community by the difference in volumetric soil-water content (0-30 cm soil depth) between replicated plots that were clipped of all vegetation and control, unclipped plots. Transpiration rates estimated under conditions of minimal soil drainage varied between 0.63 and 2.4 mm/d for the fern-graminoid community and 0.57 and 1.1 mm/d for the graminoid community over the study. The fern-graminoid community produced more biomass than the graminoid community in all years, but generally had lower transpiration rates. Severe drought in year 2002 reduced growth and transpiration of the fern-graminoid community more than the graminoid community. Evaporation rates were estimated by temporal changes in soil-water content in clipped plots during dry periods, and were 54 to 474% of transpiration rates estimated under conditions of minimal soil drainage because of the dry and windy conditions that occur at the study site. Based on this study and a study of transpiration of scattered trees invading the meadow, transpiration by the herbaceous understorey was higher than transpiration by trees during similar seasons
An Analysis of Financial and Nonfinancial Prepayment of GNMA Securities with a Varying Coefficient Model
This paper develops a model that examines the financial and nonfinancial prepayment of GNMA securities. A varying coefficient model depicts prepayment as a dynamic process, allowing for changes in factors, reflecting differences in time, debt, and borrowers' characteristics. This model provides a means for systematically incorporating hypothesized effects of nonfinancially motivated prepayment while isolating financially induced calls on the debt. Also, the model captures the impact on prepayment of interactions between financial and nonfinancial variables.
Distribution, functional impact, and origin mechanisms of copy number variation in the barley genome
BACKGROUND There is growing evidence for the prevalence of copy number variation (CNV) and its role in phenotypic variation in many eukaryotic species. Here we use array comparative genomic hybridization to explore the extent of this type of structural variation in domesticated barley cultivars and wild barleys. RESULTS A collection of 14 barley genotypes including eight cultivars and six wild barleys were used for comparative genomic hybridization. CNV affects 14.9% of all the sequences that were assessed. Higher levels of CNV diversity are present in the wild accessions relative to cultivated barley. CNVs are enriched near the ends of all chromosomes except 4H, which exhibits the lowest frequency of CNVs. CNV affects 9.5% of the coding sequences represented on the array and the genes affected by CNV are enriched for sequences annotated as disease-resistance proteins and protein kinases. Sequence-based comparisons of CNV between cultivars Barke and Morex provided evidence that DNA repair mechanisms of double-strand breaks via single-stranded annealing and synthesis-dependent strand annealing play an important role in the origin of CNV in barley. CONCLUSIONS We present the first catalog of CNVs in a diploid Triticeae species, which opens the door for future genome diversity research in a tribe that comprises the economically important cereal species wheat, barley, and rye. Our findings constitute a valuable resource for the identification of CNV affecting genes of agronomic importance. We also identify potential mechanisms that can generate variation in copy number in plant genomes.This work was financially supported by the following grants:
project GABI-BARLEX, German Federal Ministry of Education and Research
(BMBF), #0314000 to MP, US, KFXM and NS; Triticeae Coordinated
Agricultural Project, USDA-NIFA #2011-68002-30029 to GJM; and Agriculture
and Food Research Initiative Plant Genome, Genetics and Breeding Program
of USDA’s Cooperative State Research and Extension Service, #2009-65300-
05645 to GJM
Changes in ponderosa pine forests of the Mt. Trumbull Wilderness
Ponderosa pine forests in the Mt. Trumbull Wilderness on the Arizona Strip have become dense with young trees and highly susceptible to catastrophic wildfire due to exclusion of the natural frequent-fire regime. As part of a broader regional ecological restoration study, the Mt. Trumbull Wilderness was sampled for fire scarred trees, vegetation, and fuels in 1997 and 1999. Reconstructed fire histories show that fires recurred about every 4.4 years prior to settlement, with larger fires burning every 9.5 years. Frequent fires ceased after 1863 in the Mt. Trumbull Wilderness, coincident with the time of Euro-American settlement around 1870, beginning a fire-free period that has lasted up to the present except for a few small fires and a larger 1989 wildfire. Current forests are dense, averaging approximately 1,200 trees/ha, and dominated by small trees. Throughout the wilderness, tree canopy cover averages over 65(percent) and tree basal area is high, 35- 36 m2/ha. Understory plant cover is about 20(percent) and understory species diversity averages 11.4 species/sample plot. Living and dead fuels, including plants, woody debris, and the forest floor, will easily support high-intensity wildfires. In contrast, the presettlement forest was relatively open, with tree density of approximately 62 trees/ha and basal area averaging 8.9 m2/ha, dominated by large ponderosa pine trees. In ecological terms, prospects are good for restoring the Mt. Trumbull Wilderness to emulate the ecological structure and fire disturbance regime of the presettlement reference condition. The current forest condition is perhaps least affected by recent degradation of any site in the Uinkaret Mountains. However, ecological information is only one component contributing to the debate over appropriate management values and practices in wilderness areas on public lands
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