Short-term Preferences Research Articles

Intertemporális tőkeallokációs döntések tartósan alacsony kamatkörnyezetben

THE AIMS OF THE PAPER In this study, we investigate the impact of the low interest rate environment on the investment decisions. By formulating our research question, we wanted to know what kind of decision rule could describe the intertemporal preferences of decision makers in the low interest rate environment, if the traditional present value rule cannot explain the outcome of the decisions. METHODOLOGY To answer this research question we made a literature review and used numeric examples to introduce the rationally expected reaction of the decision makers. We also compared the intertemporal choices of decision makers who apply the traditional present value rule with those who have short-term preferences. During the research, we investigated the reactions of the decision makers mainly from a methodological point of view and we concentrated on the intertemporal preferences using the assumption that the reactions of the decision makers are motivated by the present value rule. We investigated the last decade after the crisis, because it is a distinct period, which enabled us to introduce the changes induced by the low interest rate environment. MOST IMPORTANT RESULTS By applying the traditional present value rule, we showed that the decrease of the discount rate stretches the time horizon of the investments and the increasing volatility of the present value provide space for speculation and for chase of returns. As the most important result of our research, we argue that in the cases when the traditional present value rule cannot explain the intertemporal preferences of decision makers we can apply quasi-hyperbolic discount functions, which can explain the decrease of investments and the increase of capital transfers. In the case of decision makers with short-term preferences the excess discounting leads to lower present values compared to the traditional present value rule, thus these decision makers can forgo valuable investment. RECOMMENDATIONS To answer our research question, we can draw the conclusion, that hyperbolic discounting and quasi-hyperbolic discount functions emerge as an alternative decision making framework of the intertemporal capital allocation decisions in contrast of the traditional present value rule in the low interest rate environment.

GACOforRec: Session-Based Graph Convolutional Neural Networks Recommendation Model

The biggest challenge to recommendation systems based on user preferences is how to improve the ability of the recommendation system to mine and analyse user preferences and behaviours. In this process, we must not only consider the continuation of the user's long-term preference but also improve the system's ability to accommodate short-term preferences and discrete preferences. To this end, we focus on the performance of time factors of user preferences. However, the issue we are concerned about has not received much attention in the existing research. We propose a new recommendation model based on the perspective of user sessions, namely GACOforRec. This model can handle long-term and stable preferences at the same time and preserve the hierarchy of potential preferences. We conducted a large number of comparative experiments on two real datasets, and the results show that GACOforRec is significantly better than other state-of-the-art methods in the study of user sessions.

Consumer preferences for different red wine styles and repeated exposure effects

As the complexity of wine flavor is strongly linked with grape quality, depending on grape-growing practices and winemaking procedures, winemakers are concerned to anticipate some stabilization of consumer preferences for specific, intrinsic, wine characteristics.The objective of our experiment was to compare the impact of tasting wine over time at home, with first impressions in a single tasting session under laboratory conditions on the preference for certain types of premium red Bordeaux wines available on the market.To assess the consistency of evaluation at home, half of the participants tasted two contrasting wines (fresh/jammy fruit, low/high alcohol) on several occasions. In both cases, traditional sensory analysis and experimental economic techniques were applied to evaluate the preferences of French consumers (N = 184) and their willingness to pay.This observation of the effect of repeated exposure to wines with high alcohol levels (15% vol.), marked by jammy fruit flavors, on the stability of appreciation of these wines clearly revealed the fragility of short-term preferences and the importance of giving consumers time to evaluate wines in a familiar atmosphere.

Life history theory and human behavior: Testing associations between environmental harshness, life history strategies and testosterone

This study was a test of associations between measures of harsher environments and indicators of a “faster” life history strategy, including higher aggression, risk taking and a sociosexuality preference for short term and uncommitted sexual relationships. Hypotheses were derived from previous literature in evolutionary psychology proposing that harsher environments promote these faster life history strategies. Additionally, due to the potential for testosterone to act as a hormonal mechanism calibrating life history strategies, associations were tested between salivary testosterone and harsher environments and faster life history strategy indicators. Based on a sample of young adult male undergraduates (n = 99), the results of this study do not support hypothesized associations between harsher environments and faster life history strategies.The majority of tests between environmental harshness and life history strategy indicators were non-significant, with two being significant in the expected direction and one being significant in the unexpected direction. However, none of these remained significant after adjustment for multiple comparisons. There were no significant associations between testosterone and environmental harshness or life history strategy indicators. The results of this study suggest reconsideration of current uses of life history theory within evolutionary psychology intended to explain relationships between environments and psychology and behavior.

Situation awareness for recommender systems

One major shortcoming of traditional recommender systems is their inability to adjust to users’ short-term preferences resulting from varying situation-specific factors. To address this, we propose the notion of situation-aware recommender systems, which are supposed to autonomously determine the users’ current situation based on a multitude of contextual side information and generate truly personalized recommendations. In particular, we develop a situation awareness model for recommender systems, include it in a situation-aware recommendation process, and derive generic design steps for the design of situation-aware recommender systems. The feasibility of these concepts is demonstrated by directly employing them for the development and implementation of a music recommender system for everyday situations. Moreover, their meaningfulness is shown by means of an empirical user study. The outcomes of the evaluation indicate a significant increase in user satisfaction compared to traditional (i.e. non-situation-aware) recommendations.

Particle size affects short-term preference behavior of brown-egg laying hens fed diets based on corn or barley

We studied the influence of particle size of the main cereal of the diet on preference behavior by laying hens. Diets formed a 2 × 5 factorial with 2 main cereals (corn vs. barley) and 5 grinding sizes of the cereal (4, 6, 8, 10, and 12mm screen). Each treatment was replicated 5 times (10 hens each). After a fasting period of 8h, hens received their respective experimental diets from 06.00 to 14.00hours. The geometric mean diameter (GMD) and the geometric standard deviation of the residuals in the feeder were determined every 2hours. In addition, CP, ash, and Ca contents of the feeds were determined at the start and at the end of the experimental period. The experimental design was completely randomized with data analyzed as repeated measures with particle size and cereal as main effects. The GMD of the original feeds increased with increases in screen size and was greater for the barley than for the corn diets. The difference in GMD between the original diets and the residuals measured at 2h intervals decreased as the experiment progressed (P < 0.001 for the interaction). Crude protein, ash, and Ca concentrated in the coarse fraction of the original diets and of the uneaten feed, an effect more pronounced for the minerals. Independent of the coarseness of the feed sieve, ash and Ca contents were higher in the uneaten feed at 14.00h than in the original diets. Hens showed a clear preference for coarse particles irrespective of the concentration of CP, ash, or Ca in the different fractions of the diets. Data showed that birds under-consumed Ca during the morning, a period in which the requirements for mineral deposition are low. In summary, hens showed a significant preference for coarser particles, an effect that was more evident when the cereals were ground coarse. Hens, however, did not show any preference for consuming those feed fractions with greater CP, ash, or Ca contents.

Specificity in Sociality: Mice and Prairie Voles Exhibit Different Patterns of Peer Affiliation.

Social behavior is often described as a unified concept, but highly social (group-living) species exhibit distinct social structures and may make different social decisions. Prairie voles (Microtus ochrogaster) are socially monogamous rodents that often reside in extended family groups, and exhibit robust preferences for familiar social partners (same- and opposite-sex) during extended choice tests, although short-term preferences are not known. Mice (Mus musculus) are gregarious and colonial, but in brief laboratory tests of social preference they typically prefer social novelty. This preference for novel vs. familiar peers may represent a species-specific difference in social decision-making between mice and prairie voles. However, the tests used to measure preferences in each species differ markedly in duration and degree of contact, such that the behaviors cannot be directly compared. We assessed whether social preferences for novelty or familiarity differed between mice and prairie voles of both sexes when assessed with matching protocols: the sociability/social preference test (SPT) typically used in mice (short, no direct contact), and the partner preference test (PPT) used in voles (long, direct contact). A subset of voles also underwent a PPT using barriers (long, no direct contact). In the short SPT, behavior did not differ between species. In the longer test, pronounced partner preferences emerged in prairie voles, but mice exhibited no social preferences and rarely huddled. No sex differences were evident in either test. Direct physical contact was required for partner preferences in huddling time in voles, but preference for the partner chamber was evident with or without contact. Both prairie voles and mice are social, but they exhibit important differences in the specificity and extent of their social behavior. While mice are often used to study social approach and other behaviors, voles are a more suitable species for the study of selective social relationships. Consideration of these differences will be important for studies examining the neural mechanisms supporting different kinds of peer social behavior.

Algorithmic Challenges to Autonomous Choice

We then explore how autonomous algorithmic assistants affect the legal framework. Some issues challenge the very use of algorithmic assistants: Should the law place an age limit on the use of such algorithms? Should legal limits be placed on their use in certain spheres? Other issues arise from the construction of preferences by algorithms. To wit, in a market in which demand is driven by algorithms, can we necessarily regard the choices made as expressions of user preferences that serve our socio-political goals? Even if the answer is positive—does this new mode of user choice fit current legal assumptions, such as those that apply to the notions of consent or intent? And are our regulatory tools, which seek to ensure that individual consumers can make informed decisions, outmoded? It is therefore essential to determine whether the existing legal framework is sufficiently potent to deal with this brave new world, or whether we need new regulatory tools. Despite their importance and timeliness, these questions have not been dealt with in depth. This article seeks to fill this void. It proceeds as follows. Part II explores the lure and modes of operation of algorithmic assistants, and how these characteristics may affect human choice. Part III then analyzes the rationales for such choice and explores how these rationales are affected by the employment of autonomous algorithmic assistants. As shown, while some rationales are not harmed—and might even be strengthened— by the use of autonomous algorithmic assistants, others challenge us to reconsider the meaning and the role that choice plays in our lives and to deal with the conflict between the efficient fulfillment of short-term preferences and the long-term ability to form such preferences. Part IV analyzes the implications of these new private orderings on regulation, with a special focus on laws based on assumptions of human autonomous decision-making. We summarize our findings in a short conclusion.

A Time-Aware Personalized Point-of-Interest Recommendation via High-Order Tensor Factorization

Recently, location-based services (LBSs) have been increasingly popular for people to experience new possibilities, for example, personalized point-of-interest (POI) recommendations that leverage on the overlapping of user trajectories to recommend POI collaboratively. POI recommendation is yet challenging as it suffers from the problems known for the conventional recommendation tasks such as data sparsity and cold start, and to a much greater extent. In the literature, most of the related works apply collaborate filtering to POI recommendation while overlooking the personalized time-variant human behavioral tendency. In this article, we put forward a fourth-order tensor factorization-based ranking methodology to recommend users their interested locations by considering their time-varying behavioral trends while capturing their long-term preferences and short-term preferences simultaneously. We also propose to categorize the locations to alleviate data sparsity and cold-start issues, and accordingly new POIs that users have not visited can thus be bubbled up during the category ranking process. The tensor factorization is carefully studied to prune the irrelevant factors to the ranking results to achieve efficient POI recommendations. The experimental results validate the efficacy of our proposed mechanism, which outperforms the state-of-the-art approaches significantly.

Ensiled sugar beets as dietary component and their effect on preference and dry matter intake by goats

ABSTRACTThis study examines the influence of ensiled sugar beets (Beta vulgaris ssp. vulgaris) on preference and short-time dry matter (DM) intake of goats. Whole sugar beets were ensiled either without any silage additive (sugar beet silage (SBS)) or with a chemical additive (6 l/t) containing 85% formic and propionic acids (treated sugar beet silage (TBS)) and were chopped after ensiling. The influence of different proportions of SBS (0%, 6.25%, 12.5%, 18.75% and 25% of dietary DM) and TBS (0%, 5%, 10%, 15% and 20% of DM) in partial mixed rations on short-time DM intake by goats (adult Saanen type wethers; n = 10) was studied in two separate, independent trials. Preference behaviour was investigated by offering the goats two different experimental diets per day and offer each possible combination of them (n = 10) once throughout the trial. On this basis, the mean DM intake (within 30 min and 3 h) of each experimental diet was determined. Both sugar beet silages showed good fermentation quality with low pH. By using the chemical silage additive, the production of ethanol was reduced and considerable amounts of sugar were preserved. In the short-term preference experiment, increasing concentrations of sugar beet silage in the ration increased DM intake (p < 0.05) in a linear way with a strong preference for those diets containing high amounts of sugar beet silage. Initial DM intake after 30 min was 4–5 fold increased for diets containing the highest beet concentration. It is assumed that the preference was positively influenced by sugar and sweet taste or the associated higher concentration of metabolisable energy.

Bactrocera oleae-induced olive VOCs routing mate searching in Psyttalia concolor males: impact of associative learning.

Olfaction is a key sense routing foraging behaviour in parasitoids. Preferences for food, mate and host stimuli can be innate in parasitic wasps. Alternatively, learning-mediated mechanisms play a crucial role. Females of the braconid parasitoid Psyttalia concolor exploit olfactory cues arising from tephritid hosts and related microhabitats. However, little is known on the olfactory stimuli routing males searching for mates. In this study, we focused on the attractiveness of Bactrocera oleae-induced olive volatiles towards P. concolor males. Furthermore, we evaluated learning occurrence in virgin males, when trained for selected unattractive volatile organic compounds (VOCs) associated with mate rewards. (E)-β-Ocimene, α-pinene and limonene attracted virgin males in Y-tube bioassays. Unattractive VOCs evoked positive chemotaxis after associative learning training. P. concolor males exposed to VOCs during a successful or unsuccessful mating, showed short-term preference for these VOCs (<1 h). However, memory consolidation was strictly dependent on reward value. Indeed, males experiencing a successful mating showed a fast consolidation into protein dependent long-term memory, appearing after 24 h. On the other hand, males experiencing a less valuable training experience (i.e. unsuccessful courtship), did not show consolidated memory after 24 h. Overall, our findings suggest that P. concolor virgin males may exploit VOCs from the host microhabitat to boost their mate searching activity, thus their reproductive success. However, since learning is a costly process, P. concolor males retained durable memories just in presence of a valuable reward, thus avoiding maladaptive behaviours.

Jus Pro Bello: The Impact of International Prosecutions on War Continuation

This Article investigates the political and military conditions under which national governments decided to invite judicial scrutiny from the International Criminal Court (ICC). The cross-case analysis of seven country situations either examined or investigated by the ICC Prosecutor's Office (OTP) lends support to the conclusion that government decisions to solicit external judicial scrutiny are a function of two main independent variables, namely their military inability to defeat the rebellion and short-term preference for continuing war over negotiating its conclusion. I hereby argue that specific values on these variables combined to persuade national governments in conflict-ridden countries that, against predictions to the contrary, inviting ICC scrutiny was in fact in their interest. This Article's contribution to the lasting debate on 'Peace v. Justice' is two-fold. First, it emphasizes state agency in processes of norm exploitation and subversion. Second, it sheds new light on the tactical use of international laws in the pursuit of broader state strategies. In all, this Article highlights the instrumentality of international laws in prolonging, rather than bringing to an end, internal conflict. In so doing, it urges scholars and practitioners to rethink the relationship between the concepts of 'justice' and 'peace,' for the former may be used to undermine the latter.

Investigating the Temporal Effect of User Preferences with Application in Movie Recommendation

As the rapid development of mobile Internet and smart devices, more and more online content providers begin to collect the preferences of their customers through various apps on mobile devices. These preferences could be largely reflected by the ratings on the online items with explicit scores. Both of positive and negative ratings are helpful for recommender systems to provide relevant items to a target user. Based on the empirical analysis of three real-world movie-rating data sets, we observe that users’ rating criterions change over time, and past positive and negative ratings have different influences on users’ future preferences. Given this, we propose a recommendation model on a session-based temporal graph, considering the difference of long- and short-term preferences, and the different temporal effect of positive and negative ratings. The extensive experiment results validate the significant accuracy improvement of our proposed model compared with the state-of-the-art methods.

Preference for and use of oral enrichment objects in juvenile silver foxes (Vulpes vulpes)

Providing captive foxes with relevant enrichment objects may support their ability to cope with barren housing systems and thus have positive welfare effects. The relevance of enrichment objects is, among others, related to animals’ preference that should be examined prior to supplementing their housing environment. In this study, we assessed 30 juvenile, singly housed silver foxes’ short-term preference for five different oral enrichment objects based on their immediate use of the objects when they were given simultaneous access after one week of deprivation. Also, wear and tear after one week of continuous access was assessed as a measure of use and to estimate the robustness and durability of various objects. A cattle femur bone was clearly the first ranked object (P≤0.05), followed by a rawhide bone, a mutual pulling device mounted between neighbouring cages, and straw and a plastic cube as the least used objects. All of the objects were, to a various degree, gnawed by the foxes. After one week of use, about 30% of the cattle bone mass was consumed, compared to about 88% of the rawhide bone mass. Although the plastic cubes were almost indestructible and therefore durable objects their low ranking do not necessarily make them good enrichment objects for foxes. Offering meat bones to captive foxes provide the animals with biologically relevant stimuli that elicit oral manipulation and play, behaviours with potential rewarding effects to the animals.

Do Individualss Risk and Time Preferences Predict Entrepreneurial Choice?

This study seeks to estimate whether individuals’ risk and time preferences are predictive of self employment status and entry. Prior Work: The low risk aversion of those who are self employed is well established in theory and empirical evidence, there is less evidence however on whether risk seeking in existing employees predicts future self employment entry and virtually no empirical research on the links between time preference and self employment. Approach: This study uses a quantitative approach by estimating a series of statistical models that estimate the relationship between an individuals’ risk and time preferences and whether they are (or subsequently become) self employed using a national longitudinal dataset. Results: We find that the self employed are more likely to have low risk aversion. When restricting our analysis to those who are initially employees we find that , low risk aversion combined with a preference for short term gains are most predictive of a transition into self employment. Implications and Value: This study informs the general question as to whether entrepreneurship is linked to personality traits with new evidence on the link between risk and time preference and self employment entry, in doing so it points towards attitudes toward risk and time preference that need to be encouraged if entrepreneurship is to be developed within countries and firms.

Influence of dietary electrolyte balance on feed preference and growth performance of postweaned piglets.

A total of 672 male and female piglets (21 d postweaning; approximately 13 kg BW) were selected to be used in 3 different experiments to assess the influence of dietary electrolyte balance (dEB; Na + K - Cl, in mEq/kg of diet) on feed preference and growth performance. In Exp. 1, piglets were fed 4 isoenergetic diets differing in dEB level: 16, 133, 152, and 269 mEq/kg diets. Changes on dEB were obtained by changing the levels of sodium and chloride with calcium chloride, calcium carbonate, and sodium bicarbonate. Piglets fed the 16 and 133 mEq/kg diets achieved a greater ADG (P < 0.04), BW (P < 0.04), and apparent total-tract digestibility of CP and Zn (P < 0.05) than did piglets fed the 269 mEq/kg diet. The 16 mEq/kg level also reduced blood total CO (P < 0.01), bicarbonate (P < 0.01), and base excess (P < 0.02) concentrations compared with the rest of the dietary treatments. Three diets differing in dEB were designed for Exp. 2 and 3: -16, 151, and 388 mEq/kg diets. In Exp. 2, greater ADFI (P = 0.03), BW (P = 0.02), ADG (P < 0.001), and G:F (P < 0.01) were observed for piglets fed the -16 mEq/kg diet than those fed the 388 mEq/kg diet. Subsequently, their short-term preference for these diets was assessed by using a 2-d choice-test protocol (30 min). Piglets preferred (P < 0.001) the 388 mEq/kg diet to the -16 mEq/kg diet, independently of the dietary treatment they received before. Pigs also preferred (P < 0.001) the 151 mEq/kg diet when compared with the -16 mEq/kg diet. Experiment 3 assessed the long-term preference and short-term consumption of the -16 and 388 mEq/kg diets. Similar to Exp. 2, animals showed a greater (P < 0.001) intake of the 388 mEq/kg diet than they did of the -16 mEq/kg diet during both the preference (14 d) and 1-feeder (2 h) tests conducted. Results show that low rather than high dEB levels optimize growth performance of piglets. When they have the opportunity to choose, piglets are unable to select the diet that optimizes their performance, either in short- or in long-term preference tests, showing also a greater short-term consumption of high instead of low dEB levels.

The effect of palatability of protein source on dietary selection in dairy calves

Evidence has shown that soybean meal is perceived as more palatable than canola meal by dairy calves in short-term preference tests. This study evaluated the effect of protein source on longer-term dietary selection of dairy calves. In experiment 1, 40 Holstein bull calves (11.4±4.3d of age) were randomly assigned to 1 of 2 choice diets for 6wk: base starter pellet (S; 12% crude protein; CP) and high-protein pellet (40% CP) containing either (1) soybean meal (SB) or (2) canola meal (CM). In wk 7 to 8, all calves were offered a single pelleted diet containing the protein source to which they were previously exposed. In experiment 2, 22 Holstein bull calves (9.9±4.6d of age) were offered, for 6wk, a choice of 2 mixed pelleted diets: (1) 70% S and 30% SB (SB mix), or (2) 70% S and 30% CM (CM mix). In wk 7 to 8, calves were randomly assigned to 1 of 2 choice diets, as in experiment 1: (1) SB + S, or (2) CM + S. All feeds were provided ad libitum. Calves received 6 L/d of milk replacer [0.75kg/d of dry matter (DM)] for the duration of both experiments. Feed intake was recorded daily and calves were weighed every 14d. Feeds were sampled weekly to analyze DM and nutrient intake. Mixed diets in experiment 2 were analyzed for CP in wk 4 and 6 to assess feed sorting (calculated as actual CP intake as a percentage of predicted intake). In experiment 1, calves offered SB + S in wk 1 to 6 consumed more high-protein pellet than calves offered CM + S [73 vs. 42% of DM intake (DMI)] and, consequently, more CP (168 vs. 117g/d). Solid feed DMI and average daily gain were similar between treatments. When offered a single diet in wk 7 to 8, calves offered starter containing soybean meal increased intake to a greater extent than calves offered the starter containing canola meal. In experiment 2, calves preferred the SB mix to CM mix (preference ratio: 0.7). Calves consumed more CP than predicted from SB mix in wk 4 and 6 (108±2.0%), indicating that they were sorting in favor of SB. In contrast, calves consumed less CP than predicted from CM mix in wk 4 (81.48±4.1%), indicating that they were sorting against CM. When assigned to choice treatments in wk 7 to 8 of experiment 2, calves offered SB + S consumed more protein pellet than calves offered CM + S (81 vs. 31% DMI) and consumed more CP (378 vs. 196g/d). Average daily gain was greater for calves offered SB + S but DMI was similar. Overall, these results suggest that dietary selection was influenced by innate feed preferences, and milk-fed calves may not be sensitive to protein imbalances in their diet.

Aerobic exposure of grass silages and its impact on dry matter intake and preference by goats

The effect of aerobic exposure of grass silages on short-term feed intake and preference by goats was studied. Eight grass silages differing in dry matter (DM) (25% and 33%), chop length (short and long) and compaction pressure at ensiling (0.1MPa and 0.2MPa) were exposed to air for eight days. Chemical analyses were conducted in 2-day (d) intervals (d0, d2, d4, d6 and d8 after silo opening) for proximate constituents, fermentation products and other volatile compounds as well as determination of microbiological status (yeasts, moulds and aerobic mesophilic bacteria). Furthermore, d0- to d8-silages were stored anaerobically in vacuum-sealed plastic bags for use in preference trials. After aerobic exposure, eight preference trials with Saanen-type wethers (n=5) were carried out, where each possible two-way combination of silages and a standard hay (n=15) was offered for 3h. Data were analyzed using the SAS procedure Multidimensional Scaling, analysis of variance and correlation analysis between silage characteristics and DM intake (DMI). All silages were aerobically stable during the examination time. In trials with 33% DM-silages, DMI decreased at d6 or d8 (in each of two trials) of aerobic exposure. Silage that had been exposed to air for 8d was avoided in each case with a reduction (mean±standard deviation) of 50±6.7% in comparison to the freshest silage. Low-DM silages showed signs of malfermentation with higher concentrations of butyric acid and ammonia-nitrogen (NH3-N). Both DMI and the impact of aerobic exposure on DMI were lower. Mean decrease in DMI after 8d of aerobic exposure was 20% (±11.0%). Products from protein and amino acid degradation (NH3-N, butyric acid) were negatively correlated to DMI (r=−0.55 and −0.59; P<0.001). It was concluded that in well-fermented silages, aerobic exposure for a length of time that is of practical relevance does have a negative impact on short-term DMI and preference by goats, even if silages are at an apparently low stage of deterioration. It is assumed that goats can detect subtle differences caused by aerobic exposure, sometimes even before an increase in temperature or changes in chemical composition occur. After a 1-d exposure of each variant, goats were able to differ between forages and showed preference or avoidance for different silages, with a high correlation between initial and total DMI. Therefore, results showed the potential for 30min measurements in short-term preference trials, as goats remember post-ingestive feedback from the adaptation period.

Consequences of asymmetric competition between resident and invasive defoliators: A novel empirically based modelling approach

Invasive species can have profound effects on a resident community via indirect interactions among community members. While long periodic cycles in population dynamics can make the experimental observation of the indirect effects difficult, modelling the possible effects on an evolutionary time scale may provide the much needed information on the potential threats of the invasive species on the ecosystem. Using empirical data from a recent invasion in northernmost Fennoscandia, we applied adaptive dynamics theory and modelled the long term consequences of the invasion by the winter moth into the resident community. Specifically, we investigated the outcome of the observed short-term asymmetric preferences of generalist predators and specialist parasitoids on the long term population dynamics of the invasive winter moth and resident autumnal moth sharing these natural enemies. Our results indicate that coexistence after the invasion is possible. However, the outcome of the indirect interaction on the population dynamics of the moth species was variable and the dynamics might not be persistent on an evolutionary time scale. In addition, the indirect interactions between the two moth species via shared natural enemies were able to cause asynchrony in the population cycles corresponding to field observations from previous sympatric outbreak areas. Therefore, the invasion may cause drastic changes in the resident community, for example by prolonging outbreak periods of birch-feeding moths, increasing the average population densities of the moths or, alternatively, leading to extinction of the resident moth species or to equilibrium densities of the two, formerly cyclic, herbivores.

Robotic Radiosurgery for the Treatment of 1–3 Brain Metastases: A Pragmatic Application of Cost-Benefit Analysis Using Willingness-To-Pay

With the emergence of radiosurgery as a new radiotherapeutic technique, health care decision makers are required to incorporate community need, cost and patient preferences when allocating radiosurgery resources. Conventional patient utility measures would not reflect short term preferences and would therefore not inform decision makers when allocating radiosurgery treatment units. The goal of this article is to demonstrate the feasibility of cost-benefit analysis to elicit the yearly net monetary benefit of robotic radiosurgery. To calculate the yearly incremental cost of robotic radiosurgery as compared to fixed gantry radiosurgery we used direct local cost data. We assumed a standard 10 year replacement and 5% amortization rate. Decision boards summarizing the clinical scenario of brain metastases and the difference between robotic and fixed gantry radiosurgery in terms of immobilization, comfort and treatment time were then presented to a sample of 18 participants. Participants who preferred robotic radiosurgery were randomly assigned to either a low ($1) or high ($5) starting point taxation based willingness-to-pay algorithm. The yearly incremental cost of providing robotic radiosurgery was $99,177 CAD. The mean community yearly willingness-to-pay for robotic radiosurgery was $2,300,000 CAD, p = 0.03. The calculated yearly net societal benefit for robotic radiosurgery was $2,200,823 CAD. Among participants who preferred robotic radiosurgery there was no evidence of starting point bias, p = 0.8. We have shown through this pilot study that it is feasible to perform cost-benefit analysis to evaluate new technologies in Radiation Oncology. Cost-benefit analysis offers an analytic method to evaluate local preferences and provide accountability when allocating limited healthcare resources.