Periodic Motions in Banach Space and Applications to Functional-Differential Equations

In establishing the existence of periodic solutions for nonautonomous differential equations of the form x = g(x, t), where g is periodic in t of period for fixed x, it is often convenient to consider the translation operator T(x(t)) = x(t + ). If corresponding to each initial vector chosen in an appropriate region there corresponds a unique solution of our equation, then periodicity may be established by proving the existence of a fixed point under T. This same technique is also useful for more general functional equations and can be extended in a number of interesting ways. In this paper we shall consider a variable type of translation operator which is useful in investigating periodicity for autonomous differential and functional equations where the period involved is less obvious

The Dynamics of US Labor Force Attachment

No abstract.

In Defense of the Land Residual Theory and the Absence of a Business Value Component for Retail Property

The temptation is strong for arguing that property values can be broken down into land, improvements, and business value, as only land and improvements are subject to property tax. As sympathetic as the authors are to this motivation, the notion of a long-run business value component for retail property is refuted and the land residual value theory reasserted, while at the same time admitting the possibility of first owner entrepreneurial or development-based value creation. It is argued that any excess property productivity will eventually become attached to the land, and last that option values are an important aspect of land values that would be affected when suggesting that the appropriate value of a given property is the cost of substituting adjacent property.

Influence of Spatial Resolution on Space-Time Disease Cluster Detection

Background: Utilizing highly precise spatial resolutions within disease outbreak detection, such as the patients’ address, is most desirable as this provides the actual residential location of the infected individual(s). However, this level of precision is not always readily available or only available for purchase, and when utilized, increases the risk of exposing protected health information. Aggregating data to less precise scales (e.g., ZIP code or county centroids) may mitigate this risk but at the expense of potentially masking smaller isolated high risk areas. Methods: To experimentally examine the effect of spatial data resolution on space-time cluster detection, we extracted administrative medical claims data for 122500 viral lung episodes occurring during 2007–2010 in Tennessee. We generated 10000 spatial datasets with varying cluster location, size and intensity at the address-level. To represent spatial data aggregation (i.e., reduced resolution), we then created 10000 corresponding datasets both at the ZIP code and county level for a total of 30000 datasets. Using the space-time permutation scan statistic and the SaTScan™ cluster software, we evaluated statistical power, sensitivity and positive predictive values of outbreak detection when using exact address locations compared to ZIP code and county level aggregations. Results: The power to detect disease outbreaks did not largely diminish when using spatially aggregated data compared to more precise address information. However, aggregations negatively impacted the ability to more accurately determine the exact spatial location of the outbreak, particularly in smaller clusters (<800 km2). Conclusions: Spatial aggregations do not necessitate a loss of power or sensitivity; rather, the relationship is more complex and involves simultaneously considering relative risk within the cluster and cluster size. The likelihood of spatially over-estimating outbreaks by including geographical areas outside the actual disease cluster increases with aggregated data

The Switch from Low-Pressure Sodium to Light Emitting Diodes Does Not Affect Bat Activity at Street Lights

We used a before-after-control-impact paired design to examine the effects of a switch from low-pressure sodium (LPS) to light emitting diode (LED) street lights on bat activity at twelve sites across southern England. LED lights produce broad spectrum 'white' light compared to LPS street lights that emit narrow spectrum, orange light. These spectral differences could influence the abundance of insects at street lights and thereby the activity of the bats that prey on them. Most of the bats flying around the LPS lights were aerial-hawking species, and the species composition of bats remained the same after the switch-over to LED. We found that the switch-over from LPS to LED street lights did not affect the activity (number of bat passes), or the proportion of passes containing feeding buzzes, of those bat species typically found in close proximity to street lights in suburban environments in Britain. This is encouraging from a conservation perspective as many existing street lights are being, or have been, switched to LED before the ecological consequences have been assessed. However, lighting of all spectra studied to date generally has a negative impact on several slow-flying bat species, and LED lights are rarely frequented by these 'light-intolerant' bat species

Cryogenic Propulsion Stage (CPS) Configuration in Support of NASA's Multiple Design Reference Missions (DRMs)

In support of the National Aeronautics and Space Administration's (NASA) Human Exploration and Operations Mission Directorate (HEOMD), the Space Launch System (SLS) is being designed for safe, affordable, and sustainable human and scientific exploration missions beyond Earth's or-bit (BEO). The SLS Team is tasked with developing a system capable of safely and repeatedly lofting a new fleet of spaceflight vehicles beyond Earth orbit. The Cryogenic Propulsion Stage (CPS) is a key enabler for evolving the SLS capability for BEO missions. This paper reports on the methodology and initial recommendations relative to the CPS, giving a brief retrospective of early studies on this promising propulsion hardware. This paper provides an overview of the requirements development and CPS configuration in support of NASA's multiple Design Reference Missions (DRMs)

Apparent Change in Ion Selectivity Caused by Changes in Intracellular K+ during Whole-Cell Recording

AbstractIn whole-cell recordings from HEK293 cells stably transfected with the delayed rectifier K+ channel Kv2.1, long depolarizations produce current-dependent changes in [K+]i that mimic inactivation and changes in ion selectivity. With 10mM Ko+ or Ki+, and 140–160mM Nai,o+, long depolarizations shifted the reversal potential (VR) toward ENa. However, similar shifts in VR were observed when Nai,o+ was replaced with N-methyl-d-glucamine (NMG+)i, o. In that condition, [K+]o did not change significantly, but the results could be quantitatively explained by changes in [K+]i. For example, a mean outward K+ current of 1 nA for 2s could decrease [K+]i from 10mM to 3mM in a 10pF cell. Dialysis by the recording pipette reduced but did not fully prevent changes in [K+]i. With 10mM Ki,o+, 150mM Nai+, and 140mM NMGo+, steps to +20mV produced a positive shift in VR, as expected from depletion of Ki+, but opposite to the shift expected from a decreased K+/Na+ selectivity. Long steps to VR caused inactivation, but no change in VR. We conclude that current-dependent changes in [K+]i need to be carefully evaluated when studying large K+ currents in small cells