9,120 research outputs found
Optimizing passive acoustic sampling of bats in forests
Passive acoustic methods are increasingly used in biodiversity research and monitoring programs because they are cost-effective and permit the collection of large datasets. However, the accuracy of the results depends on the bioacoustic characteristics of the focal taxa and their habitat use. In particular, this applies to bats which exhibit distinct activity patterns in three-dimensionally structured habitats such as forests. We assessed the performance of 21 acoustic sampling schemes with three temporal sampling patterns and seven sampling designs. Acoustic sampling was performed in 32 forest plots, each containing three microhabitats: forest ground, canopy, and forest gap. We compared bat activity, species richness, and sampling effort using species accumulation curves fitted with the clench equation. In addition, we estimated the sampling costs to undertake the best sampling schemes. We recorded a total of 145,433 echolocation call sequences of 16 bat species. Our results indicated that to generate the best outcome, it was necessary to sample all three microhabitats of a given forest location simultaneously throughout the entire night. Sampling only the forest gaps and the forest ground simultaneously was the second best choice and proved to be a viable alternative when the number of available detectors is limited. When assessing bat species richness at the 1-km(2) scale, the implementation of these sampling schemes at three to four forest locations yielded highest labor cost-benefit ratios but increasing equipment costs. Our study illustrates that multiple passive acoustic sampling schemes require testing based on the target taxa and habitat complexity and should be performed with reference to cost-benefit ratios. Choosing a standardized and replicated sampling scheme is particularly important to optimize the level of precision in inventories, especially when rare or elusive species are expected
The cost of surgical training: analysis of operative time for laparoscopic cholecystectomy
Background: Duration of surgery is a main cost factor of surgical training. The purpose of this analysis of operative times for laparoscopic cholecystectomies (LC) was to quantify the extra time and related costs in regards to the surgeons' experience in the operating room (OR). Methods: All LC performed between January 01, 2005 and December 31, 2008 in 46 hospitals reporting to the database of the Swiss Association for Quality Management in Surgery (AQC) were analyzed (n=10,010). Four levels of seniority were specified: resident (R), junior consultant (JC), senior consultant (SC), and attending surgeon (AS). The differences in operative time according to seniority were investigated in a multivariable log-linear and median regression analysis controlling for possible confounders. The OR costs were calculated by using a full cost rate in a teaching hospital. Results: A total of 9,208 LC were available for analysis; 802 had to be excluded due to missing data (n=212) or secondary major operations (n=590). Twenty-eight percent of the LC were performed by R as teaching operations (n=2,591). Compared with R, the multivariable analysis of operative time showed a median difference of â2.5min (â9.0; 4.8) for JC and â18min (â25; â11) for SC and â28min (â35; â10) for AS, respectively. The OR minute costs were âŹ17.57, resulting in incremental costs of âŹ492 (159; 615) per operation in case of tutorial assistance. Conclusions: The proportion of LC performed as tutorial assistance for R remains low. Surgical training in the OR causes relevant case-related extra time and therefore cost
Fatigue life extension of existing welded structures via high frequency mechanical impact (HFMI) treatment
High-Frequency Mechanical Impact (HFMI) is one of the post-weld treatment methods. In this study, comparative axial fatigue tests were conducted on as-welded and HFMI-treated welded transverse attachment details. The test results demonstrated the efficiency of HFMI-treatment in fatigue life extension of cracked welded structures, providing that the existing crack size is less than 1.2 mm. Cracks were created in some specimens through fatigue testing before HFMI-treatment, while other specimens were not subjected to any fatigue loading prior to treatment. Many of the treated specimens ran out after 10 million cycles of loading when tested at a stress range of 150 MPa. Therefore, the stress range was increased to 180 MPa or 210 MPa. No remarkable difference was found between the fatigue strength of the crack-free and the cracked treated specimens. It was found that the induced compressive residual stress can exceed the material yield limit, and reach a depth larger than 1.5 mm in most cases. The induced compressive residual stress, the local material hardening, the increase in weld toe radius, the change in crack orientation and the shallowness of the crack size were the causatives of the obtained long fatigue lives of the HFMI-treated specimens. Besides, linear elastic fracture mechanics calculations were conducted to predict the fatigue lives of as-welded and HFMI-treated details. The results were in agreement with the experiment. Moreover, the calculations showed that the initial crack size, the clamping stress and the induced compressive residual stress were the main factors behind the scatter in fatigue lives
Crack detection via strain measurements in fatigue testing
Fatigue cracks have appeared as a significant issue for joints and connections in existing steel structures in the last decades. Therefore, those are a major inspection and maintenance matter for any steel structure\u27s operator. This emphasises the importance of using a reliable detection method to determine the crack size and assessing the severity of such a crack on the structural integrity of a structure. In this article, the effectiveness of strain measurement in detecting fatigue cracks in transversal nonâload carrying welded attachment subjected to out of plane axial loading is studied. Numerical analysis and experimental investigations allowed to correlate the decrease in strain measured by attached gauges to the crack depth at the weld toe. In addition, different strain evolution patterns were found during fatigue testing, and the fracture surfaces of the specimens were observed to interpret these patterns. Moreover, the crack position with respect to the weld toe surface was predicted via strain measurements
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Target Zones in History and Theory: Lessons from an Austro-Hungarian Experiment (1896-1914)
The first known experiment with an exchange rate band took place in Austria-
Hungary between 1896 and 1914. The rationale for introducing this policy rested
on precisely those intuitions that the modern literature has emphasized: the band
was designed to secure both exchange rate stability and monetary policy
autonomy. However, unlike more recent experiences, such as the ERM, this
policy was not undermined by credibility problems. The episode provides an ideal
testing ground for some important ideas in modern macroeconomics: specifically,
can formal rules, when faithfully adhered to, provide policy makers with some
advantages such as short term autonomy? First, we find that a credible band has a
"microeconomic" influence on exchange rate stability. By reducing uncertainty, a
credible fluctuation band improves the quality of expectations, a channel that has been neglected in the modern literature. Second, we show that the standard test of the basic target zone model is flawed and develop an alternative methodology. We believe that these findings shed a new light on the economics of exchange rate bands
Simplicial quantum dynamics
Present-day quantum field theory can be regularized by a decomposition into
quantum simplices. This replaces the infinite-dimensional Hilbert space by a
high-dimensional spinor space and singular canonical Lie groups by regular spin
groups. It radically changes the uncertainty principle for small distances.
Gaugeons, including the gravitational, are represented as bound fermion-pairs,
and space-time curvature as a singular organized limit of quantum
non-commutativity.
Keywords: Quantum logic, quantum set theory, quantum gravity, quantum
topology, simplicial quantization.Comment: 25 pages. 1 table. Conference of the International Association for
Relativistic Dynamics, Taiwan, 201
Relativistic and Radiative Energy Shifts for Rydberg States
We investigate relativistic and quantum electrodynamic effects for
highly-excited bound states in hydrogenlike systems (Rydberg states). In
particular, hydrogenic one-loop Bethe logarithms are calculated for all
circular states (l = n-1) in the range 20 <= n <= 60 and successfully compared
to an existing asymptotic expansion for large principal quantum number n. We
provide accurate expansions of the Bethe logarithm for large values of n, for
S, P and circular Rydberg states. These three expansions are expected to give
any Bethe logarithms for principal quantum number n > 20 to an accuracy of five
to seven decimal digits, within the specified manifolds of atomic states.
Within the numerical accuracy, the results constitute unified, general formulas
for quantum electrodynamic corrections whose validity is not restricted to a
single atomic state. The results are relevant for accurate predictions of
radiative shifts of Rydberg states and for the description of the recently
investigated laser-dressed Lamb shift, which is observable in a strong
coherent-wave light field.Comment: 8 pages; RevTeX
Age, retirement and health as factors in volunteering in later life
Volunteering in later life attracts attention because its benefits older volunteers, voluntary associations, and society. Unfortunately, researchers and practitioners struggle with the complexity of predicting who volunteers. The authors ask whether a rough identification of older volunteers solely based on age is possible. The authors answer this question by means of structural equation modeling, analyzing international survey data. The findings show that the direct effect of age on the time older people spend volunteering is negligible. Moreover, the age patterns in volunteering created by retirement and declining health are weak. Those findings make age an unsuitable indicator for volunteering in later life. The authors recommend that voluntary organizations and policy makers use personal characteristics, such as health status, when defining their target groups for programs that encourage volunteering. In addition, researchers should not use an age group when referring to the third age, meaning the active and productive part of old age
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