Effects of habitat composition and landscape structure on worker foraging distances of five bumblebee species

Bumblebees (Bombus spp.) are important pollinators of both crops and wild flowers. Their contribution to this essential ecosystem service has been threatened over recent decades by changes in land use, which have led to declines in their populations. In order to design effective conservation measures it is important to understand the effects of variation in landscape composition and structure on the foraging activities of worker bumblebees. This is because the viability of individual colonies is likely to be affected by the trade-off between the energetic costs of foraging over greater distances and the potential gains from access to additional resources. We used field surveys, molecular genetics and fine resolution remote sensing to estimate the locations of wild bumblebee nests and to infer foraging distances across a 20 km2 agricultural landscape in southern England. We investigated five species, including the rare B. ruderatus and ecologically similar but widespread B. hortorum. We compared worker foraging distances between species and examined how variation in landscape composition and structure affected foraging distances at the colony level. Mean worker foraging distances differed significantly between species. Bombus terrestris, B. lapidarius and B. ruderatus exhibited significantly greater mean foraging distances (551 m, 536 m, 501 m, respectively) than B. hortorum and B. pascuorum (336 m, 272 m, respectively). There was wide variation in worker foraging distances between colonies of the same species, which was in turn strongly influenced by the amount and spatial configuration of available foraging habitats. Shorter foraging distances were found for colonies where the local landscape had high coverage and low fragmentation of semi-natural vegetation, including managed agri-environmental field margins. The strength of relationships between different landscape variables and foraging distance varied between species, for example the strongest relationship for B. ruderatus being with floral cover of preferred forage plants. Our findings suggest that favourable landscape composition and configuration has the potential to minimise foraging distances across a range of bumblebee species. There is thus potential for improvements in the design and implementation of landscape management options, such as agri-environment schemes, aimed at providing foraging habitat for bumblebees and enhancing crop pollination services

Dependence of Cavitation Bubble Size on Pressure Amplitude at Therapeutic Levels

High‐intensity, focused ultrasound therapy is a minimally invasive therapy technique that is effective and relatively safe. It can be used in areas including histotripsy, thermal ablation, and administering medication. Inertial cavitation is used to improve these therapy methods. The purpose of this study was to determine the effect of pressure amplitude on cavitation resonance frequency/bubble size at therapeutic field levels. Earlier work has indicated that the resonance size depends on pressure amplitude; however, the investigation only considered pressure amplitudes up to 1 MPa [1]. Our study was conducted by simulating the response of bubbles to linearly propagating sine waves using the Gilmore‐Akulichev formulation to solve for the bubble response. The frequency of the sine wave varied from 1 to 5 MHz while the amplitude of the sine wave varied from 0.0001 to 9 MPa. The resonance size for a particular frequency of excitation and amplitude was determined by finding the initial bubble size that resulted in the maximum bubble expansion for an air bubble in water. The simulations demonstrated a downshift in resonance size with increasing pressure amplitude. Therefore, smaller bubbles will have a more dramatic response to ultrasound at therapeutic levels

Giraffes, Institutions and Neglected Firms

Certain securities - in particular, those of small capitalization firms - are generally unsuited to the investment requirements of financial institutions, hence attract minimal coverage by analysts. As a result, these securities may offer a premium as a compensation for associated information deficiencies and/or because pricing inefficiencies exist as a result of the lack of information. An analysis of 510 firms over a 10-year period indicates that the shares of those firms neglected by institutions outperform significantly the shares of firms widely held by institutions. The superior performance persists over and above any small firm effect ; that is, both small and medium-sized neglected firms exhibit superior performance. The neglected firm effect suggests some potentially rewarding investment strategies for individuals and institutions alike

Sensory-Based Interventions in the School Setting: Perspectives of Paraeducators

Sensory experiences or environmental modifications can: Regulate behavior Improve sensory modulation Improve readiness for activities Improve focus for learnin

A Comparison of Static Measures of Liquidity to Integrative Measures of Financial and Operating Liquidity: An Application to Restaurant Operators and Restaurant Franchisors

The results presented in this paper show that integrative financial and operating measures of liquidity provide investors and creditors with information beyond that provided by static measures of short-term liquidity such as the current and quick ratios. Using a sample of restaurant firms over the period 1994–2003, our analysis shows dynamic measures of liquidity provide a drastically different view of short-term solvency than those produced from the static measures. Static measures of liquidity imply that restaurant companies are not liquid. However, when evaluated under this integrative framework, restaurant companies were shown to be more liquid than their current and quick ratios implied. Thus, financial analysts, creditors, and managers should evaluate both static and dynamic liquidity measures when evaluating the short-term financial liquidity and short-term credit worthiness of firms. In addition, careful attention should be paid to both financial and operating measures of liquidity to establish what changes, if any, have occurred in a company\u27s liquidity position over time. This is an important finding for managers and investors in all industries, since short-term illiquidity implies a high risk of default if the banks refuse to refinance all or part of the debt. This in turn may affect the cost of short-term financing and result in an impact on their overall financing costs and required returns from equity investors

Managing farmed landscapes for pollinating insects

Increasing floral resources and improving habitat conditions can benefit pollinating insect species, wildflowers and crop production

Analyst Forecasts and Price/Earnings Ratios

[Excerpt] Security valuation techniques have become increasingly sophisticated, as evidenced by advances in option pricing theory and Arbitrage Pricing Theory (APT). Despite the availability of these paradigms, the price/earnings (P/E) approach to security valuation has maintained its popularity among practicing security analysts. Much of this lasting popularity can be attributed to the apparent simplicity of the P/E approach and the difficulties inherent in implementing complex valuation models. To implement the P/E approach, analysts must estimate the appropriate P/E multiple, which typically requires the development of a model. Unfortunately, most of the P/E models that have been developed use ad hoc empirical tests and historical data. One notable exception is a study by Cragg and Malkiel, which tested a theoretical P/E model using analysts\u27 forecasts for a nonrandom sample of 175 large firms. This note extends the work of Cragg and Malkiel in two ways. First, it is not restricted to large firms; all firms with complete data are included in the empirical tests. Second, the model includes some factors not considered by other researchers

Exotic Reservations – Low Price Guarantees

The increase in the volume of internet online bookings has had a major impact on distribution channels in the hotel industry. The popularity of such services stems from the consumers\u27 desire to obtain the lowest rate within their desired market segment. One possible cure is to offer the best rate guarantee. We show that current rate guarantees are essentially worthless to consumers; and demonstrate how a hotel company can structure a best rate guarantee that would provide value to consumers. In addition, we show, using a well-established exotic option pricing formula, how to price this best rate guarantee so that consumers would be willing to pay for the option

Effects of an agri-environment scheme on bumblebee reproduction at local and landscape scales

Agri-environment schemes (AES) have been implemented across Europe, aiming to mitigate effects of habitat loss in agro-ecosystems for a range of declining species. These include pollinating insects such as bumblebees, for which positive effects of AES on abundance and species richness have been shown. However, there is a lack of evidence for effects of AES on reproduction of target species, at either local or landscape scales. We conducted a large-scale study across landscapes exhibiting a gradient of agricultural intensity to investigate the effects of a targeted flower mixture, sown in patches of three different sizes, on an index of the total biomass of bumblebee sexuals (males and queens) on replicated transects within each landscape. We used this index (MQ) as a measure of bumblebee reproduction. After controlling for floral density on transects, we found that MQ was significantly higher on sown flower patches than on conventionally managed control patches at local scales throughout the three-year study. While sown flower patches did not significantly increase MQ in surrounding landscapes, MQ was higher in landscapes surrounding larger (1. ha) than smaller (0.25. ha) sown patches. Our results suggest that, while responses of different bee species may vary depending on the plant species sown, targeted flower mixtures can enhance bumblebee reproduction by providing locally attractive forage resources to bumblebees of all castes and sexes from nests within foraging distance. If established at large enough scales, sown flower patches may lead to a detectable spill-over of reproductives into surrounding landscapes. Furthermore, effects of sown patches on MQ were moderated by landscape context, the strongest positive responses being detected at sites with high proportions of arable land. This supports previous findings that AES can deliver greater net benefits for pollinators in more intensively farmed landscapes.This research was funded by the UK Department for Environment, Food and Rural Affairs (research grant BD1625), and Natural England, Peterborough, UK