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Tradeoff
Kinds of Tradeoff Selected AbstractsThe Influence of Flowing Water on the Resource Pursuit-Risk Avoidance Tradeoff in the Crayfish Orconectes virilisETHOLOGY, Issue 4 2006Keith W. Pecor The influence of hydrodynamics on chemically mediated behavioral tradeoffs has received little attention. We tested the hypothesis that individuals of the crayfish Orconectes virilis would be more sensitive to chemical cues in flowing water than in still water. Orconectes virilis is a good subject for this test, because it is found in both still water (e.g. ponds), and flowing water (e.g. rivers). A factorial design was used, with two stimulus treatments and two habitat types. Crayfish were exposed to either food cue or food + alarm cue in either still water or flowing water in an artificial stream arena. Habitat use and activity were significantly influenced by stimulus treatment, with more time spent away from the stimulus source and less activity in the food + alarm treatment than in the food treatment. Neither habitat type nor the interaction of stimulus treatment and habitat type had a significant effect on the response variables. Given the natural history of O. virilis, we suggest that selection has favored the ability to equally utilize chemical cues in both still and flowing water. We acknowledge that different flow conditions may influence chemical ecology in this species and caution against the view that tests in flowing waters necessarily provide a more accurate approximation of natural responses. [source] A Reexamination of the Tradeoff between the Future Benefit and Riskiness of R&D IncreasesJOURNAL OF ACCOUNTING RESEARCH, Issue 1 2008ALLAN EBERHART ABSTRACT Many previous studies document a positive relation between research and development (R&D) and equity value. Though R&D can increase equity value by increasing firm value, it can also increase equity value at the expense of bondholder wealth through an increase in firm risk because equity is analogous to a call option on the underlying firm value. Shi [2003] tests this hypothesis by examining the relation between a firm's R&D intensity and its bond ratings and risk premiums at issuance. His results show that the net effect of R&D is negative for bondholders. We reexamine Shi's [2003] findings and in so doing make three contributions to the literature. First, we find that Shi's [2003] results are sensitive to the method of measuring R&D intensity. When we use what we argue is a better measure of R&D intensity, we find that the net effect of R&D is positive for bondholders. Second, when we use tests that Shi [2003] recognizes are even better than the ones that he uses, we find even stronger evidence of the positive effect of R&D on bondholders. Third, we examine cross-sectional differences in the effect of R&D on debtholders. Consistent with our main finding, we document a negative relation between R&D increases and default risk. The default risk reduction is also more pronounced for firms with higher initial default scores (where the debtholders have more to gain from an R&D increase) and for firms with more bank debt (where the debtholders have greater covenant protection from the possible detriments associated with R&D increases). [source] Cost analysis of proton exchange membrane fuel cell systemsAICHE JOURNAL, Issue 7 2008Ai-Jen Hung Abstract Tradeoff between capital cost and the operating cost can be seen in the design of proton exchange membrane fuel cell systems. The polarization curve indicates that operating in the region of lower current densities implies less operating cost (hydrogen fuel) and higher capital cost (larger membrane electrode assembly area). The opposite effects are observed when one operates in the region of higher current densities. Therefore, an appropriate design should take both factors into account and the optimality depends on the corresponding costs of hydrogen and membrane area. An analytical cost model is constructed to describe such an economic balance in a proton exchange membrane fuel cell system. The objective function of the optimization is the total annual cost. Six scenarios are used to illustrate the optimal design based on the total annual cost as cost and materials factors fluctuate. © 2008 American Institute of Chemical Engineers AIChE J, 2008 [source] On the Risk,Downside Risk TradeoffTHE MANCHESTER SCHOOL, Issue 2 2004Carmen F. Menezes In the last decade the literature has established the empirical importance of the tradeoff between risk and downside risk in a variety of economic settings. While the notions of risk and downside risk have been generalized in the theoretical literature, the literature has yet to provide a choice-theoretic characterization of their tradeoff. This paper provides an analytical characterization of the risk,downside risk tradeoff and shows its relevance in the analysis of optimal decisions under uncertainty, such as the precautionary savings decision. [source] Tradeoffs and thresholds in the effects of nitrogen addition on biodiversity and ecosystem functioning: evidence from inner Mongolia GrasslandsGLOBAL CHANGE BIOLOGY, Issue 1 2010YONGFEI BAI Abstract Nitrogen (N) deposition is widely considered an environmental problem that leads to biodiversity loss and reduced ecosystem resilience; but, N fertilization has also been used as a management tool for enhancing primary production and ground cover, thereby promoting the restoration of degraded lands. However, empirical evaluation of these contrasting impacts is lacking. We tested the dual effects of N enrichment on biodiversity and ecosystem functioning at different organizational levels (i.e., plant species, functional groups, and community) by adding N at 0, 1.75, 5.25, 10.5, 17.5, and 28.0 g N m,2 yr,1 for four years in two contrasting field sites in Inner Mongolia: an undisturbed mature grassland and a nearby degraded grassland of the same type. N addition had both quantitatively and qualitatively different effects on the two communities. In the mature community, N addition led to a large reduction in species richness, accompanied by increased dominance of early successional annuals and loss of perennial grasses and forbs at all N input rates. In the degraded community, however, N addition increased the productivity and dominance of perennial rhizomatous grasses, with only a slight reduction in species richness and no significant change in annual abundance. The mature grassland was much more sensitive to N-induced changes in community structure, likely as a result of higher soil moisture accentuating limitation by N alone. Our findings suggest that the critical threshold for N-induced species loss to mature Eurasian grasslands is below 1.75 g N m,2 yr,1, and that changes in aboveground biomass, species richness, and plant functional group composition to both mature and degraded ecosystems saturate at N addition rates of approximately 10.5 g N m,2 yr,1. This work highlights the tradeoffs that exist in assessing the total impact of N deposition on ecosystem function. [source] Administering the class: Tradeoffs and balancing characterize the tasks after a mediated settlementALTERNATIVES TO THE HIGH COST OF LITIGATION, Issue 5 2005Margaret L. Shaw Last month, Margaret L. Shaw, of New York, and Linda R. Singer, of Washington, D.C., described mediation use in class action cases; in the second of two parts this month, they dissect the challenges in administering a class action settlement. [source] Optimal control of innate immune responseOPTIMAL CONTROL APPLICATIONS AND METHODS, Issue 2 2002Robert F. Stengel Abstract Treatment of a pathogenic disease process is interpreted as the optimal control of a dynamic system. Evolution of the disease is characterized by a non-linear, fourth-order ordinary differential equation that describes concentrations of pathogens, plasma cells, and antibodies, as well as a numerical indication of patient health. Without control, the dynamic model evidences sub-clinical or clinical decay, chronic stabilization, or unrestrained lethal growth of the pathogen, depending on the initial conditions for the infection. The dynamic equations are controlled by therapeutic agents that affect the rate of change of system variables. Control histories that minimize a quadratic cost function are generated by numerical optimization over a fixed time interval, given otherwise lethal initial conditions. Tradeoffs between cost function weighting of pathogens, organ health, and use of therapeutics are evaluated. Optimal control solutions that defeat the pathogen and preserve organ health are demonstrated for four different approaches to therapy. It is shown that control theory can point the way toward new protocols for treatment and remediation of human diseases. Copyright © 2002 John Wiley & Sons, Ltd. [source] Tradeoffs and sexual conflict over women's fertility preferences in MpimbweAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 4 2009Monique Borgerhoff Mulder There are two principle evolutionary models for why women reduce their fertility, which can be used to explain the modern demographic transition. The first derives from optimality theory (specifically the "quantity-quality" tradeoff hypothesis), and the second from models of biased cultural transmission ("prestige bias" and "kin influence" hypotheses). Data on family planning preferences collected in 1996 and 1998 in a rural African village (in Mpimbwe, Tanzania) are used to test predictions derived from each hypothesis and show that both "quantity-quality" tradeoffs and biased cultural transmission underlie Pimbwe women's decisions. Reproductive decisions, however, are not made in a vacuum. Men and women's ideal family sizes often differ, and sexual conflict is particularly likely to affect a woman's success in limiting her family size. Pimbwe women's reproductive output between the initial family planning survey in 1996 and the most recent demographic survey (2006) is analyzed in relation to both the woman's preferences to limit her family and her exposure to husbands and husbands' kin. Despite wide differences in desired family sizes between men and women the extent of sexual conflict in this population is restricted to husbands and wives, and affects not a woman's use or planned use of modern contraception but her success in employing such methods effectively. There is also some evidence that a woman's mother and her kin assist in the use and effective use of modern methods, offering a prevailing force to the high-fertility objectives of the husband. Am. J. Hum. Biol., 2009. © 2009 Wiley-Liss, Inc. [source] Public Preferences for Program Tradeoffs: Community Values for Budget PrioritiesPUBLIC BUDGETING AND FINANCE, Issue 1 2004Glenn C. Blomquist A growing literature concerns techniques to improve community-based reforms and citizen-centered governance in order to reinforce the trust in democratic government. We analyze a contingent choice technique that systematically collects information about individual citizens' relative values of a set of state public programs. Individual citizens are asked to allocate a fixed increment of public funds. Individuals reveal their marginal willingness to trade off (MWTTO) additions in one program for additions in another. MWTTO values provide program rankings and information concerning the relative strength of citizen preferences. An example of a contingent choice survey is described. [source] Intertemporal Tradeoffs for Gains and Losses: An Experimental Measurement of Discounted Utility,THE ECONOMIC JOURNAL, Issue 545 2010Mohammed Abdellaoui This article provides a parameter-free measurement of utility in intertemporal choice and presents new and more robust evidence on the discounting of money outcomes. Intertemporal utility was concave for gains and convex for losses, consistent with a hypothesis put forward by Loewenstein and Prelec (1992). Discount rates declined over time but less so than previously observed under the assumption of linear utility. For approximately 40% of our subjects constant discounting provided the best fit. The remaining 60% were most consistent with Harvey's (1986) power discounting. Our data provide little support for the popular quasi-hyperbolic model, which is widely used in economics today. We observed an asymmetry in the discounting of gains and losses that, unlike earlier findings, cannot be explained by a framing effect. [source] Conflict and Compromise Over Tradeoffs in Universal Health Insurance PlansTHE JOURNAL OF LAW, MEDICINE & ETHICS, Issue 3 2004Mark V. Pauly First page of article [source] Variation and covariation of life history traits in aphids are related to infection with the facultative bacterial endosymbiont Hamiltonella defensaBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2010LUIS E. CASTAÑEDA Host,symbiont associations play an important role in insects. In aphids, facultative symbionts affect host plant use and increase thermal tolerance and resistance to natural enemies. In spite of these beneficial effects on aphid fitness, the frequency of facultative symbionts in aphids ranges from low to intermediate. Tradeoffs induced by symbionts could prevent the fixation of symbionts in aphid populations. Therefore, we studied the life history traits and correlations between them in 21 clones of the black bean aphid, Aphis fabae, seven of which were infected with the facultative endosymbiont Hamiltonella defensa. We found that clones harbouring H. defensa exhibited significantly higher body mass at maturity and offspring production, and a marginally higher intrinsic rate of increase. However, development time and offspring body size did not differ between symbiont-free and infected clones. In addition, body mass at maturity was positively correlated with offspring production, offspring body size and intrinsic rate of increase, whereas development time was negatively correlated with body mass at maturity, offspring production and offspring body size. Excluding infected clones had little effect on these correlations; only correlations between body mass at maturity and offspring production, and between development time and offspring body size, became nonsignificant. Therefore, we did not find any evidence for tradeoffs between life history traits induced by symbiont infection. In fact, infected clones had higher overall fitness than symbiont-free clones under the conditions of our experiment, suggesting that symbionts do not impose costs on aphids harbouring them. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 237,247. [source] Quantifying Process Tradeoffs in the Operation of Chromatographic SequencesBIOTECHNOLOGY PROGRESS, Issue 4 2003Sheau-Huey Ngiam A method for the rapid representation of key process tradeoffs that need to be made during the analysis of chromatographic sequences has been proposed. It involves the construction of fractionation and maximum purification factor versus yield diagrams, which can be completed easily on the basis of chromatographic data. The output of the framework developed reflects the degree of tradeoff between levels of yield and purity and provides a fast and precise prediction of the sample fraction collection strategy needed to meet a desired process specification. The usefulness of this approach for the purposes of product purification and contaminant removal in a single chromatographic step has been successfully demonstrated in an earlier paper and it is now extended by application to a chromatographic sequence: the separation of a hypothetical three-component protein system by hydrophobic interaction chromatography (HIC) followed by size exclusion chromatography (SEC). The HIC operation has a strong impact upon the subsequent SEC step. The studies show how the analysis of performance in such a chromatographic sequence can be carried out easily and in a straightforward fashion using the fractionation diagram approach. The methodology proposed serves as a useful tool for identifying the process tradeoffs that must be made during operation of a sequence of chromatographic steps and indicates the impact on further processing of the cut-point decisions that are made. [source] Strategy Tradeoffs in the Knowledge and Network EconomyBUSINESS STRATEGY REVIEW, Issue 1 2001Øystein D. Fjeldstad In traditional "value chain" firms, the main activity tradeoff is between differentiation and low cost. Increasingly, however, firms are creating customer value through networks (eg AOL) or by providing knowledge-based solutions for customers (eg venture capital firm Kleiner Perkins). This article discusses the quite different activity tradeoffs faced by these "value networks" and "value shops". It then explores the tradeoff between exploitation (focusing on short-term performance) and exploration (focusing on transcending short-term activity tradeoffs). Finally, in reviewing the implications for managers, it discusses the problem of trying to manage different types of business (value chains, networks and shops) within the same corporation. [source] Reinterpretable Imager: Towards Variable Post-Capture Space, Angle and Time Resolution in PhotographyCOMPUTER GRAPHICS FORUM, Issue 2 2010Amit Agrawal Abstract We describe a novel multiplexing approach to achieve tradeoffs in space, angle and time resolution in photography. We explore the problem of mapping useful subsets of time-varying 4D lightfields in a single snapshot. Our design is based on using a dynamic mask in the aperture and a static mask close to the sensor. The key idea is to exploit scene-specific redundancy along spatial, angular and temporal dimensions and to provide a programmable or variable resolution tradeoff among these dimensions. This allows a user to reinterpret the single captured photo as either a high spatial resolution image, a refocusable image stack or a video for different parts of the scene in post-processing. A lightfield camera or a video camera forces a-priori choice in space-angle-time resolution. We demonstrate a single prototype which provides flexible post-capture abilities not possible using either a single-shot lightfield camera or a multi-frame video camera. We show several novel results including digital refocusing on objects moving in depth and capturing multiple facial expressions in a single photo. [source] A Polymorphic Dynamic Network Loading ModelCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 2 2008Nie Yu (Marco) The polymorphism, realized through a general node-link interface and proper discretization, offers several prominent advantages. First of all, PDNL allows road facilities in the same network to be represented by different traffic flow models based on the tradeoff of efficiency and realism and/or the characteristics of the targeted problem. Second, new macroscopic link/node models can be easily plugged into the framework and compared against existing ones. Third, PDNL decouples links and nodes in network loading, and thus opens the door to parallel computing. Finally, PDNL keeps track of individual vehicular quanta of arbitrary size, which makes it possible to replicate analytical loading results as closely as desired. PDNL, thus, offers an ideal platform for studying both analytical dynamic traffic assignment problems of different kinds and macroscopic traffic simulation. [source] A Multiobjective and Stochastic System for Building Maintenance ManagementCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 5 2000Z. Lounis Building maintenance management involves decision making under multiple objectives and uncertainty, in addition to budgetary constraints. This article presents the development of a multiobjective and stochastic optimization system for maintenance management of roofing systems that integrates stochastic condition-assessment and performance-prediction models with a multiobjective optimization approach. The maintenance optimization includes determination of the optimal allocation of funds and prioritization of roofs for maintenance, repair, and replacement that simultaneously satisfy the following conflicting objectives: (1) minimization of maintenance and repair costs, (2) maximization of network performance, and (3) minimization of risk of failure. A product model of the roof system is used to provide the data framework for collecting and processing data. Compromise programming is used to solve this multiobjective optimization problem and provides building managers an effective decision support system that identifies the optimal projects for repair and replacement while it achieves a satisfactory tradeoff between the conflicting objectives. [source] The Neutralizer: a self-configurable failure detector for minimizing distributed storage maintenance costCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 2 2009Zhi Yang Abstract To achieve high data availability or reliability in an efficient manner, distributed storage systems must detect whether an observed node failure is permanent or transient, and if necessary, generate replicas to restore the desired level of replication. Given the unpredictability of network dynamics, however, distinguishing permanent and transient failures is extremely difficult. Though timeout-based detectors can be used to avoid mistaking transient failures as permanent failures, it is unknown how the timeout values should be selected to achieve a better tradeoff between detection latency and accuracy. In this paper, we address this fundamental tradeoff from several perspectives. First, we explore the impact of different timeout values on maintenance cost by examining the probability of their false positives and false negatives. Second, we propose a self-configurable failure detector called the Neutralizer based on the idea of counteracting false positives with false negatives. The Neutralizer could enable the system to maintain a desired replication level on average with the least amount of bandwidth. We conduct extensive simulations using real trace data from a widely deployed peer-to-peer system and synthetic traces based on PlanetLab and Microsoft PCs, showing a significant reduction in aggregate bandwidth usage after applying the Neutralizer (especially in an environment with a low average node availability). Overall, we demonstrate that the Neutralizer closely approximates the performance of a perfect ,oracle' detector in many cases. Copyright © 2008 John Wiley & Sons, Ltd. [source] Effect of redundancy on the mean time to failure of wireless sensor networksCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 8 2007Anh Phan Speer Abstract In data-driven wireless sensor networks (WSNs), the system must perform data sensing and retrieval and possibly aggregate data as a response at runtime. As a WSN is often deployed unattended in areas where replacements of failed sensors are difficult, energy conservation is of primary concern. While the use of redundancy is desirable in terms of satisfying user queries to cope with sensor and transmission faults, it may adversely shorten the lifetime of the WSN, as more sensor nodes will have to be used to answer queries, causing the energy of the system to drain quickly. In this paper, we analyze the effect of redundancy on the mean time to failure (MTTF) of a WSN in terms of the number of queries the system is able to answer correctly before it fails due to either sensor/transmission faults or energy depletion. In particular, we analyze the effect of redundancy on the MTTF of cluster-structured WSNs for energy conservations. We show that a tradeoff exists between redundancy and MTTF. Furthermore, an optimal redundancy level exists such that the MTTF of the system is maximized. Copyright © 2007 John Wiley & Sons, Ltd. [source] Refactoring service-based systems: how to avoid trusting a workflow serviceCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 10 2006Howard Chivers Abstract Grid systems span multiple organizations, so their workflow processes have security requirements, such as restricting access to data or ensuring that process constraints are observed. These requirements are often managed by the workflow component, because of the close association between this sub-system and the processes it enacts. However, high-quality security mechanisms and complex functionality are difficult to combine, so designers and users of workflow systems are faced with a tradeoff between security and functionality, which is unlikely to provide confidence in the security implementation. This paper resolves that tension by showing that process security can be enforced outside the workflow component. Separating security and process functionality in this way improves the quality of security protection, because it is implemented by standard system mechanisms; it also allows the workflow component to be deployed as a standard service, rather than a privileged system component. To make this change of design philosophy accessible outside the security community it is documented as a collection of refactorings, which include problem templates that identify suspect design practice, and target patterns that provide solutions. Worked examples show that these patterns can be used in practice to implement practical applications, with both traditional workflow security concerns, and Grid requirements. Copyright © 2005 John Wiley & Sons, Ltd. [source] Ontogenetic switches from plant resistance to tolerance: minimizing costs with age?ECOLOGY LETTERS, Issue 3 2007Karina Boege Abstract Changes in herbivory and resource availability during a plant's development should promote ontogenetic shifts in resistance and tolerance, if the costs and benefits of these basic strategies also change as plants develop. We proposed and tested a general model to detect the expression of ontogenetic tradeoffs for these two alternative anti-herbivory strategies in Raphanus sativus. We found that ontogenetic trajectories occur in both resistance and tolerance but in opposite directions. The juvenile stage was more resistant but less tolerant than the reproductive stage. The ontogenetic switch from resistance to tolerance was consistent with the greater vulnerability of young plants to leaf damage and with the costs of resistance and tolerance found at each stage. We posit that the ontogenetic perspective presented here will be helpful in resolving the current debate on the existence and detection of a general resistance,tolerance tradeoff. [source] Tax and Education Policy in a Heterogeneous-Agent Economy: What Levels of Redistribution Maximize Growth and Efficiency?ECONOMETRICA, Issue 2 2002Roland Bénabou This paper studies the effects of progressive income taxes and education finance in a dynamic heterogeneous-agent economy. Such redistributive policies entail distortions to labor supply and savings, but also serve as partial substitutes for missing credit and insurance markets. The resulting tradeoffs for growth and efficiency are explored, both theoretically and quantitatively, in a model that yields complete analytical solutions. Progressive education finance always leads to higher income growth than taxes and transfers, but at the cost of lower insurance. Overall efficiency is assessed using a new measure that properly reflects aggregate resources and idiosyncratic risks but, unlike a standard social welfare function, does not reward equality per se. Simulations using empirical parameter estimates show that the efficiency costs and benefits of redistribution are generally of the same order of magnitude, resulting in plausible values for the optimal rates. Aggregate income and aggregate welfare provide only crude lower and upper bounds around the true efficiency tradeoff. [source] Long-Term Debt and Optimal Policy in the Fiscal Theory of the Price LevelECONOMETRICA, Issue 1 2001John H. Cochrane The fiscal theory says that the price level is determined by the ratio of nominal debt to the present value of real primary surpluses. I analyze long-term debt and optimal policy in the fiscal theory. I find that the maturity structure of the debt matters. For example, it determines whether news of future deficits implies current inflation or future inflation. When long-term debt is present, the government can trade current inflation for future inflation by debt operations; this tradeoff is not present if the government rolls over short-term debt. The maturity structure of outstanding debt acts as a "budget constraint" determining which periods' price levels the government can affect by debt variation alone. In addition, debt policy,the expected pattern of future state-contingent debt sales, repurchases and redemptions,matters crucially for the effects of a debt operation. I solve for optimal debt policies to minimize the variance of inflation. I find cases in which long-term debt helps to stabilize inflation. I also find that the optimal policy produces time series that are similar to U.S. surplus and debt time series. To understand the data, I must assume that debt policy offsets the inflationary impact of cyclical surplus shocks, rather than causing price level disturbances by policy-induced shocks. Shifting the objective from price level variance to inflation variance, the optimal policy produces much less volatile inflation at the cost of a unit root in the price level; this is consistent with the stabilization of U.S. inflation after the gold standard was abandoned. [source] The Choice Among Interbank Settlement Systems: The European ExperienceECONOMIC NOTES, Issue 1 2003Angelo Baglioni This paper addresses the choice of banks between alternative channels for interbank payments. The conventional view assumes a tradeoff between the safety of real-time gross settlement (RTGS) and the liquidity savings of multilateral netting. Moreover, correspondent banking is believed to be inefficient, both in terms of liquidity and of administrative costs. In the last decade, however, the impulse of the Committee on Payment and Settlement Systems, technological changes and the management of RTGS systems by central banks have reduced the difference between the various systems. This is especially true for risk, whereas liquidity cost crucially depends on the refinancing policy adopted by the central bank and the co-ordination among the participants. On the basis of the recent evolution of payment systems in Europe, we verify the importance of liquidity, as well as other variables like transaction costs, for the choice of banks among different settlement systems. Cost factors imply that the nature of payments flows (value, commercial versus financial) and some structural features of the banking systems (dimension of the intermediaries, concentration of the banking sector) become important. The analysis is carried out both through a theoretical model and a cross-country comparison based on three data sources: ECB (European Central Bank, EBA (Euro Banking Association) and SWIFT (Society for Worldwide Interbank Financial Telecommunication). [source] SPECIAL INTEREST POLITICS AND INTELLECTUAL PROPERTY RIGHTS: AN ECONOMIC ANALYSIS OF STRENGTHENING PATENT PROTECTION IN THE PHARMACEUTICAL INDUSTRYECONOMICS & POLITICS, Issue 2 2008ANGUS C. CHU Since the 1980s, the pharmaceutical industry has benefited substantially from a series of policy changes that have strengthened the patent protection for brand-name drugs as a result of the industry's political influence. This paper incorporates special interest politics into a quality-ladder model to analyze the policy-makers' tradeoff between the socially optimal patent length and campaign contributions. The welfare analysis suggests that the presence of a pharmaceutical lobby distorting patent protection is socially undesirable in a closed-economy setting but may improve social welfare in a multi-country setting, which features an additional efficiency tradeoff between monopolistic distortion and international free riding on innovations. [source] Diversity of the Vocal Signals of Concave-Eared Torrent Frogs (Odorrana tormota): Evidence for Individual SignaturesETHOLOGY, Issue 11 2009Albert S. Feng Male concave-eared torrent frogs (Odorrana tormota) have an unusually large call repertoire and have been shown to communicate ultrasonically. We investigated the individual specificity of male advertisement calls in order to explore the acoustic bases of individual recognition, which was demonstrated in an accompanying study. Vocalizations of 15 marked males were recorded in the field. A quantitative analysis of the signals revealed eight basic call-types. Two of them (the single- and multi-note long-calls) were investigated in more detail. Long-calls were characterized by pronounced and varying frequency modulation patterns, and abundant occurrence of nonlinear phenomena (NLP), i.e., frequency jumps, subharmonics, biphonations and deterministic chaos. The occurrence of NLP was predictable from the contour of the fundamental frequency in the harmonic segment preceding the onset of the NLP, and this prediction showed individual-specific patterns. Fifteen acoustic variables of the long calls were measured, all of which were significantly different among individuals, except biphonic segment duration. Discriminant function analysis (DFA) showed that 54.6% of the calls could be correctly assigned to individual frogs. The correct classification was above chance level, suggesting that individual specificity of calls underlie the ability of males to behaviorally discriminate the vocal signals of their neighbors from those of strangers, a remarkable feat for a frog species with a diverse vocal repertoire. The DFA classification results were lower than those for other anurans, however. We hypothesize that there is a tradeoff between an increase in the fundamental frequency of vocalizations to avoid masking by low-frequency ambient background noise, and a decrease in individual-specific vocal tract information extractable from the signal. [source] Iterative channel estimation and data detection in frequency-selective fading MIMO channels,EUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 5 2004Maja Lon Signals transmitted through multiple-input multiple-output (MIMO) wireless channels suffer from multiple-access interference (MAI), multipath propagation and additive noise. Iterative multiuser receiver algorithms mitigate these signal impairments, while offering a good tradeoff between performance and complexity. The receiver presented in this paper performs channel estimation, multiuser detection and decoding in an iterative manner. The estimation of the frequency selective, block-fading channel is initiated with the pilot symbols. In subsequent iterations, soft decisions of all the data symbols are used in an appropriate way to improve the channel estimates. This approach leads to significant improvement of the overall receiver performance, compared to other schemes. The bit-error-rate (BER) performance of the receiver is evaluated by simulations for different parameter setups. Copyright © 2004 AEI. [source] Broadband wireless access based on VSF-OFCDM and VSCRF-CDMA and its experimentsEUROPEAN TRANSACTIONS ON TELECOMMUNICATIONS, Issue 3 2004Hiroyuki Atarashi This paper presents broadband packet wireless access schemes based on variable spreading factor (VSF)-orthogonal frequency and code division multiplexing (OFCDM) in the downlink and variable spreading and chip repetition factors (VSCRF)-CDMA in the uplink for the systems beyond IMT-2000. In our design concept for wireless access in both links, radio parameters such as the spreading factor (SF) are optimally controlled so that the system capacity is maximized according to the cell configuration, channel load and radio channel conditions, based on the tradeoff between efficient suppression of other-cell interference and the capacity increase in the target cell by exploiting orthogonality in the time and frequency domains. We demonstrate that the peak throughput of greater than 100,Mbps and 20,Mbps is achieved by the implemented base station and mobile station transceivers using the 100-MHz and 40-MHz bandwidths in the downlink and uplink respectively. Moreover, the simulation results show the possibility of the peak throughput of approximately 1,Gbps for short-range area applications using the 100-MHz bandwidth OFCDM downlink by applying four-branch multiple input multiple output (MIMO) multiplexing with 16,QAM data modulation and punctured turbo coding. Copyright © 2004 AEI [source] Ontogenetic selection on hatchery salmon in the wild: natural selection on artificial phenotypesEVOLUTIONARY APPLICATIONS (ELECTRONIC), Issue 4 2010Michael M. Bailey Abstract Captive rearing often alters the phenotypes of organisms that are destined for release into the wild. Natural selection on these unnatural phenotypes could have important consequences for the utility of captive rearing as a restoration approach. We show that normal hatchery practices significantly advance the development of endangered Atlantic salmon (Salmo salar) fry by 30+ days. As a result, hatchery fry might be expected to face strong natural selection resulting from their developmental asynchrony. We investigated patterns of ontogenetic selection acting on hatchery produced salmon fry by experimentally manipulating fry development stage at stocking. Contrary to simple predictions, we found evidence for strong stabilizing selection on the ontogeny of unfed hatchery fry, with weaker evidence for positive directional selection on the ontogeny of fed fry. These selection patterns suggest a seasonally independent tradeoff between abiotic or biotic selection favoring advanced development and physiological selection linked to risk of starvation in unfed fry. We show, through a heuristic exercise, how such selection on ontogeny may exacerbate problems in restoration efforts by impairing fry productivity and reducing effective population sizes by 13,81%. [source] Capital Allocation and Risk Performance Measurement In a Financial InstitutionFINANCIAL MARKETS, INSTITUTIONS & INSTRUMENTS, Issue 5 2000Stuart M. Turnbull This paper provides an analytical and practical framework, consistent with maximizing the wealth of existing shareholders, to address the following questions: What are the costs associated with economic capital? What is the tradeoff between the probability of default and the costs of economic capital? How do we take into account the time profile of economic capital when assessing the performance of a business? What is the appropriate measure of profitability, keeping the probability of default constant? It is shown that the capital budgeting decision depends not only on the covariance of the return of a project with the market portfolio, but also on the covariance with the bank's existing assets. This dependency arises from the simple fact that the economic capital is not additive. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||||||||