369 research outputs found
Aspects of an Interior Stream Clam Midden from 1915 at Quasqueton, Buchanan County Iowa
During clam surveys on the Wapsipinicon River in 1991 buried clams were observed in a bank of the river at Quasqueton, Buchanan County, Iowa. An interview with the landowner revealed that the clams were from a 1915 local clamming operation. Excavation and examination of many of the clams reveal interesting differences in species composition and size, when compared to more recent specimens from the river. Observations on the midden were recorded, species determinations were made and measurements were taken. Comparisons are made to two other modern surface surveys on the river. Differences were observed in both species composition and shell size
The Status of Iowa\u27s Lepidoptera
Including strays, 122 species of butterflies have been confirmed in Iowa. However, since European settlement the populations of taxa of Iowa Lepidoptera have declined. While certain generalist species have experienced declines, species with life cycles that include native habitats, especially prairies and wetlands, have been particularly vulnerable. In a 1994 revision of the Iowa endangered and threatened species list, the Natural Resource Commission (NRC) listed two species of butterflies as endangered, five as threatened, and 25 as special concern, using general legal definitions of those rankings (NRC 1994). But after examining recent records, we have revised that list, using numbers of remaining sites as a scale of rarity. Of the 100 species of resident butterflies, one species is believed extirpated, eight are critically endangered, 15 are endangered, and 21 are threatened. Iowa\u27s moth fauna is poorly sampled but may show similar trends of decline in restricted habitats. Monitoring and habitat preservation efforts are ongoing. However, the effects of current efforts to manage lepidoptera populations are unproven and may even be detrimental. With continued habitat fragmentation, pesticide use, succession, and fire management, Lepidoptera diversity in Iowa is likely to continue to decline. Preservation of native remnants and management plans that recognize the key role of invertebrates are essential for the long-term health of remnant ecosystems
Excited by a quantum field: Does shape matter?
The instantaneous transition rate of an arbitrarily accelerated Unruh-DeWitt
particle detector on four-dimensional Minkowski space is ill defined without
regularisation. We show that Schlicht's regularisation as the zero-size limit
of a Lorentz-function spatial profile yields a manifestly well-defined
transition rate with physically reasonable asymptotic properties. In the
special case of stationary trajectories, including uniform acceleration, we
recover the results that have been previously obtained by a regularisation that
relies on the stationarity. Finally, we discuss evidence for the conjecture
that the zero-size limit of the transition rate is independent of the detector
profile.Comment: 7 pages, uses jpconf. Talk given at NEB XII (Nafplio, Greece, 29 June
- 2 July 2006
Considerations on the Unruh Effect: Causality and Regularization
This article is motivated by the observation, that calculations of the Unruh
effect based on idealized particle detectors are usually made in a way that
involves integrations along the {\em entire} detector trajectory up to the
infinitely remote {\em future}. We derive an expression which allows
time-dependence of the detector response in the case of a non-stationary
trajectory and conforms more explicitely to the principle of causality, namely
that the response at a given instant of time depends only on the detectors {\em
past} movements. On trying to reproduce the thermal Unruh spectrum we are led
to an unphysical result, which we trace down to the use of the standard
regularization t\to t-i\eps of the correlation function. By consistently
employing a rigid detector of finite extension, we are led to a different
regularization which works fine with our causal response function.Comment: 19 pages, 2 figures, v2: some minor change
Der Bruch der Theorie in der Praxis durch Not
Some Remarks on Lujo Brentano's View of Labor Market Problems
Lujo Brentano (1844-1931) aimed for "realism" in economics. Regarding labor market theory, two topics are of particular interest: His investigations on "Hours and Wages in Relation to Production" (Scribner's 1894) and his analysis "On the History and Development of Gilds and the Origins of Trade Unions" (Trubner 1870). The topics of are discussed with a view on recent developments in labor economics.Lujo Brentano (1844-1931) hat sich als "realistischen" Ökonomen verstanden. Im Bereich der Arbeitsmarkttheorie sind zwei Bereiche von besonderem Interesse: Seine Untersuchungen über den Zusammenhang zwischen Lohn, Arbeitszeit und Arbeitsleistung und seine Überlegungen zur Bildung von kollektiven Formen der Lohnsetzung. Diese beiden Themen werden unter Einbeziehung gesamtwirtschaftlicher und methodischer Aspekte und einiger moderner Gesichtspunkte diskutiert
How to Investigate Within-Subject Associations between Physical Activity and Momentary Affective States in Everyday Life: A Position Statement Based on a Literature Overview
Several meta-analyses have investigated the association between physical activity and affective states and have found evidence suggesting that exercise exerts a positive effect on affective state. However, in this field of research, most studies have conducted between-subject analyses. Nonetheless, there is more and more interest in the within-subject associations between physical activity and momentary affective states in everyday life. This position statement pertains to this up-and-coming field of research and provides methodological recommendations for further studies. The paper is divided into three parts:First, we summarise and evaluate three methodological requirements necessary for the proper evaluation of within-subject associations between physical activity and momentary affective states in everyday life. We propose that the following issues should be considered: a) to address the dynamic nature of such relationships, repeated assessments are necessary; b) as activities performed in everyday life are mostly spontaneous and unconscious, an objective assessment of physical activity is useful; c) given that recall of affective states is often affected by systematic distortions, real-time assessment is preferable. In sum, we suggest the use of ambulatory assessment techniques, and more specifically the combination of acceloremeter-assessment of physical activity with an electronic diary assessment of the momentary affective state and additional context information. Second, we summarise 22 empirical studies published between 1980 and 2012 using ambulatory assessment to investigate within-subject associations between momentary affective states and physical activity in everyday life. Generally, the literature overview detects a positive association, which appears stronger among those studies that were of high methodological quality.Third, we propose the use of ambulatory assessment intervention strategies to change people's behaviour (ambulatory assessment in
How often does the Unruh-DeWitt detector click? Regularisation by a spatial profile
We analyse within first-order perturbation theory the instantaneous
transition rate of an accelerated Unruh-DeWitt particle detector whose coupling
to a massless scalar field on four-dimensional Minkowski space is regularised
by a spatial profile. For the Lorentzian profile introduced by Schlicht, the
zero size limit is computed explicitly and expressed as a manifestly finite
integral formula that no longer involves regulators or limits. The same
transition rate is obtained for an arbitrary profile of compact support under a
modified definition of spatial smearing. Consequences for the asymptotic
behaviour of the transition rate are discussed. A number of stationary and
nonstationary trajectories are analysed, recovering in particular the Planckian
spectrum for uniform acceleration.Comment: 30 pages, 1 figure. v3: Added references and minor clarification
On the Response of Particle Detectors in Vaidya Spacetimes
Using the formalism of the interaction picture we calculate an expression for
the Wightman function for only the spherically symmetric modes of a quantum
Klein-Gordon scalar field in a general Vaidya spacetime with ingoing null dust.
It is demonstrated that particle detectors following time-like trajectories
that are in the ground state at some time outside of the collapsing shell will
respond independently from the configuration of the ingoing null dust if the
response is taken at any time outside of the collapsing shell. For detectors
that are taken to be in the ground state at a time interior to the shell it is
shown that their response will depend on the configuration of the ingoing null
dust. Relevance to the information loss paradox is discussed.Comment: 14 pages, 2 figure
Transition rate of the Unruh-DeWitt detector in curved spacetime
We examine the Unruh-DeWitt particle detector coupled to a scalar field in an
arbitrary Hadamard state in four-dimensional curved spacetime. Using smooth
switching functions to turn on and off the interaction, we obtain a
regulator-free integral formula for the total excitation probability, and we
show that an instantaneous transition rate can be recovered in a suitable
limit. Previous results in Minkowski space are recovered as a special case. As
applications, we consider an inertial detector in the Rindler vacuum and a
detector at rest in a static Newtonian gravitational field. Gravitational
corrections to decay rates in atomic physics laboratory experiments on the
surface of the Earth are estimated to be suppressed by 42 orders of magnitude.Comment: 27 pages, 1 figure. v3: Typos corrected. Published versio
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