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Little Direct Evidence (little + direct_evidence)

Distribution by Scientific Domains
Business, Economics, Finance and Accounting40%

Selected Abstracts

Female canaries that respond and discriminate more between male songs of different quality have a larger song control nucleus (HVC) in the brain

DEVELOPMENTAL NEUROBIOLOGY, Issue 4 2002
Stefan Leitner
Abstract In male songbirds the song control pathway in the forebrain is responsible for song production and learning. In most species, females do not sing and have smaller nuclei in the song control pathway. Although the function of the pathway in females is assumed to be associated with the perception of male song, there is little direct evidence to support this view. In this study on female canaries, we investigate the role of two key nuclei in the song control pathway (HVC and lMAN) in relation to playback of male song. Male canaries produce elaborate songs that function to attract and stimulate females. The songs are constructed from smaller units called syllables, and special syllables with a more complex structure (sexy syllables) are known to induce females to perform copulation solicitation displays (CSD) as an invitation to mate. By using computer-edited experimental songs, we first show that females discriminate between songs by producing significantly more CSD to those containing sexy syllables. We then sectioned the brains and used in situ hybridization to reveal song nuclei containing androgen receptors. We report positive correlations between the size of HVC and both total CSD response and the amount of discrimination between sexy and nonsexy songs. We found no such relationships between these measures and the size of lMAN. These results provide some evidence to support the view that, in female canaries HVC is involved in female perception and discrimination of male song. The results also have implications for the evolution of complex male songs by sexual selection and female choice. © 2002 Wiley Periodicals, Inc. J Neurobiol 52: 294,301, 2002 [source]

Geomechanical simulation to predict open subsurface fractures

GEOPHYSICAL PROSPECTING, Issue 2 2009
Helen Lewis
ABSTRACT Geomechanical simulation of the evolution of a geological structure can play an important role in predicting open fracture development for all stages in that structure's development. In this work, three such geomechanical simulations are used to predict the evolving stress and strain fields, including dilational and compactional changes in the rock fabric in developing fault and fold systems. Their consequences for open fracture development and flow are addressed. These simulated stress and strain fields show considerable spatial and temporal heterogeneity that is consistent with deformation patterns observed in both natural examples and in laboratory-deformed analogues. But the stress and strain states that develop are neither co-axial nor do they bear a simple relationship to one another. The dilational and compactional strains, manifest as open fracturing or sealing, represent some significantly increased or significantly decreased flow rates. However, open-fracture predictions based on such geomechanical simulations are extremely difficult to validate with any degree of confidence as there is little direct evidence of sub-surface fracture distributions. In this context we also discuss possible integration of seismic anisotropy measurements, as an independent measure of open fracture alignment, to support the geomechanically derived fracture predictions. The focus of this work is on volumetric strains in fault zone evolution, though folding is also addressed. [source]

Brand specific responses to smokeless tobacco in a rat lip canal model

JOURNAL OF ORAL PATHOLOGY & MEDICINE, Issue 6 2010
Joel L. Schwartz
J Oral Pathol Med (2010) 39: 453,459 Background:, Different compositions of smokeless tobacco (ST) are widely thought to cause oral carcinoma at different rates but there is little direct evidence for this hypothesis. Methods:, We used a rat lip canal model to examine the mucosal changes induced by chronic daily exposure to four different brands of ST: Skoal, Copenhagen, Ettan Swedish Snus, and Stonewall, differing in measured levels of: tobacco specific nitrosamines (TSNAs), unprotonated nicotine, moisture, and pH. Results:, Exposure to the lip canal for 12 months produced changes in the mucosa marked by increases in S phase and M phase cells for the Skoal and Copenhagen exposed rats. This correlated with the high level of TSNAs and nicotine in these products. All the tobacco products, to different degrees, induced sites of moderate to severe dysplasia some with extensive rete peg outgrowth from the oral mucosa not seen in the controls. Many of these sites showed a loss of p16 expression. Conclusions:, While all ST products caused dysplasia, the products with lower levels of TSNAs and unprotonated nicotine caused less, consistent with the model that tobacco with low levels of nitrosamines might potentially induce fewer carcinomas in human users. [source]

Corporate investments and growth options

MANAGERIAL AND DECISION ECONOMICS, Issue 8 2007
Jeffrey J. Reuer
Real options theory models certain corporate investments as investments in growth options, yet there is little direct evidence on whether firms actually capture growth option value from these investments. In the current paper, we attempt to bridge this empirical gap, and we also examine the conditions under which the growth option value embedded in such investments is enhanced. Results from a sample of manufacturing firms during 1989,2000 reveal that investments in research and development and joint venture (JV) investments contribute to firms' growth option values. We also show that, among JVs of different ownership structures, only minority JVs increase growth option value. Our findings affirm options theory's assertion that real options can help firms capture valuable upside opportunities, they highlight the value of examining contingencies that drive option value, and they also point to the challenges firms face in realizing the unique benefits the theory emphasizes. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Was kann die Aktive Arbeitsmarktpolitik in Deutschland aus der Evaluationsforschung in anderen europäischen Ländern lernen?

PERSPEKTIVEN DER WIRTSCHAFTSPOLITIK, Issue 2 2002
Viktor Steiner
Most evaluation studies for Germany's active labor market policy (ALMP) indicate that subsidized employment programs in the public sector (public works programs, "Arbeitsbeschaffungsmaßnahmen") and publicly funded training programs have, on average, no or even negative effects on individual re-employment probabilities. This paper provides possible explanations for the ineffectiveness of these programs, where we focus on heterogeneous treatment effects, which are not accounted for in the German evaluation studies due to lack of data, and locking-in effects, in particular related to the relatively high level of income support for participants in these programs. Since there is very little direct evidence on these effects for Germany to date, we draw on results from evaluation studies for other European countries. We argue that the success of ALMP is to a large extent determined by design features like the targeting of particular groups and the incentives from the co-ordination with unemployment insurance as well as the incentives of program administrators and local governments. [source]