Quantitative Microbial Risk Assessment of Cryptosporidiosis and Giardiasis from Very Small Private Water Supplies

This article reports a quantitative microbial risk assessment of the risk of Giardia and Cryptosporidium in very small private water supplies. Both pathogens have been implicated in causing outbreaks of waterborne disease associated with such supplies, though the risk of endemic disease is not known. For exposure assessments, we used existing data to derive regression equations describing the relationships between the concentration of these pathogens and Escherichia coli in private water supplies. Pathogen concentrations were then estimated using national surveillance data of E. coli in private water supplies in England and France. The estimated risk of infection was very high with the median annual risk being of the order of 25–28% for Cryptosporidium and 0.4% to 0.7% for Giardia, though, in the poorer quality supplies the risk could be much higher. These risks are substantially greater than for public water supplies and well above the risk considered tolerable. The observation that observed infection rates are generally much lower may indicate increased immunity in people regularly consuming water from private supplies. However, this increased immunity is presumed to derive from increased disease risk in young children, the group most at risk from severe disease.     

淡季中酒店与OTA合作模式选择研究

针对淡季时酒店入住率下降的困境,将"互联网+"背景与收益管理理论相结合,通过构建Stackelberg博弈模型,研究了淡季时酒店与在线旅游代理商（Online Travel Agent,OTA）如何选择合作模式以提高入住率和收益。研究在几种常见情境下展开,不同情境下均得出了最优合作模式。优化的合作模式不但协调了酒店服务供应链,而且在提高酒店整体效益的同时,也增加了OTA的收益。研究为酒店和OTA提供了具有可操作意义上的合作模式决策支持,同时也弥补了以往研究在酒店和OTA合作模式对比、选择与优化方面的空缺。     

促销模式下基于纳什谈判的线上旅行商与线下旅行社定价策略研究

本文针对O2O模式下线下旅行社（TO）与线上旅行商（OTA）在采取促销手段时的定价策略进行研究。首先根据促销成本的承担对象划分出由TO单独承担促销成本和TO与OTA共同承担促销成本这两种促销模式，然后通过纳什谈判确定销售佣金的定价策略，研究TO与OTA的谈判能力不同且双方承担的促销成本比例变化的情况下旅游产品和促销努力水平的定价策略。结果表明：当TO的谈判能力越大时，TO所需付出的销售佣金越小，促销的努力水平越高，销售价格越低，且TO的利润越大；而且，OTA的利润随着TO谈判能力的提高而下降。此外，通过对两种促销模式下TO的利润、OTA的利润以及整体利润的对比分析得出，应依据TO与OTA共同承担促销的这种促销模式下TO承担促销的比例来确定采用的促销模式。     

Impartial Nominations for a Prize

A group of peers must choose one of them to receive a prize; everyone cares only about winning, not about who gets the prize if someone else. An award rule is impartial if one's message never influences whether or not one wins the prize. We explore the consequences of impartiality when each agent nominates a single (other) agent for the prize. On the positive side, we construct impartial nomination rules where both the influence of individual messages and the requirements to win the prize are not very different across agents. Partition the agents in two or more districts, each of size at least 3, and call an agent a local winner if he is nominated by a majority of members of his own district; the rule selects a local winner with the largest support from nonlocal winners, or a fixed default agent in case there is no local winner. On the negative side, impartiality implies that ballots cannot be processed anonymously as in plurality voting. Moreover, we cannot simultaneously guarantee that the winner always gets at least one nomination, and that an agent nominated by everyone else always wins.     

Improving Weight of Evidence Approaches to Chemical Evaluations

Federal and other regulatory agencies often use or claim to use a weight of evidence (WoE) approach in chemical evaluation. Their approaches to the use of WoE, however, differ significantly, rely heavily on subjective professional judgment, and merit improvement. We review uses of WoE approaches in key articles in the peer‐reviewed scientific literature, and find significant variations. We find that a hypothesis‐based WoE approach, developed by Lorenz Rhomberg et al., can provide a stronger scientific basis for chemical assessment while improving transparency and preserving the appropriate scope of professional judgment. Their approach, while still evolving, relies on the explicit specification of the hypothesized basis for using the information at hand to infer the ability of an agent to cause human health impacts or, more broadly, affect other endpoints of concern. We describe and endorse such a hypothesis‐based WoE approach to chemical evaluation.     

Risk Ranking for Foodborne Microbial Hazards in New Zealand: Burden of Disease Estimates

Priority setting for food safety management at a national level requires risks to be ranked according to defined criteria. In this study, two approaches (disability‐adjusted life years (DALYs) and cost of illness (COI)) were used to generate estimates of the burden of disease for certain potentially foodborne diseases (campylobacteriosis, salmonellosis, listeriosis (invasive, perinatal, and nonperinatal), infection with Shiga toxin‐producing Escherichia coli (STEC), yersiniosis, and norovirus infection) and their sequelae in New Zealand. A modified Delphi approach was used to estimate the food‐attributable proportion for these diseases. The two approaches gave a similar ranking for the selected diseases, with campylobacteriosis and its sequelae accounting for the greatest proportion of the overall burden of disease by far.     

A Psychometric Evaluation of the Expectations,Perceptions, and Difference‐Scores Generated by the IS‐Adapted SERVQUAL Instrument

This article describes the results of a study assessing the psychometric properties of the expectations and perceptions‐of‐performance instruments and the difference‐score data contained within the information systems (IS)‐Adapted SERVQUAL measurement paradigm. The central claim of this study is: In order for rational inferences to be made about service expectations, service performance perceptions, or the gap between them, each of the two instruments must exhibit reasonable psychometric properties in isolation before difference‐scores are taken. Analysis of data from a field study (N= 401) through structural equation modeling (SEM) techniques produces empirical evidence indicating that both of the instruments exhibit low psychometric quality and yet the difference‐scores exhibit “psychometric inflation.” That is, the quality of the difference‐score data is in many ways apparently superior to the raw data from both instruments. Negative conclusions are reached as to the efficacy of either individual instrument and, thus, the full IS‐Adapted SERVQUAL paradigm. Questions and prospects for further research in this important area of service quality measurement/management are presented, and a potentially rich future for IS service quality is outlined. It is strongly suggested that future IS service quality research be based on development of a new instrument, grounded in attributes endemic to IS services and developed using the best available development techniques.     

Stochastic Choice and Consideration Sets

We model a boundedly rational agent who suffers from limited attention. The agent considers each feasible alternative with a given (unobservable) probability, the attention parameter, and then chooses the alternative that maximizes a preference relation within the set of considered alternatives. We show that this random choice rule is the only one for which the impact of removing an alternative on the choice probability of any other alternative is asymmetric and menu independent. Both the preference relation and the attention parameters are identified uniquely by stochastic choice data.     

The Time Structure of Self‐Enforcing Agreements

A principal and an agent enter into a sequence of agreements. The principal faces an interim participation constraint at each date, but can commit to the current agreement; in contrast, the agent has the opportunity to renege on the current agreement. We study the time structure of agreement sequences that satisfy participation and no‐deviation constraints and are (constrained) efficient. We show that every such sequence must, after a finite number of dates, exhibit a continuation that maximizes the agent's payoff over all such efficient, self‐enforcing sequences. Additional results are provided for situations with transferable payoffs.     

A Risk Assessment Method for Biological Introductions

This article describes an application of a method for assessing risks associated with the introduction of an organism into a new environment. The test organism was a binucleate Rhizoctonia fungal isolate that has potential for commercial development as a biological control agent for damping-off diseases in bedding plants. A test sample of host plant species was selected using the centrifugal phylogenetic host range principles, but with an emphasis on economic species. The effect of the fungus on the plant was measured for each species and expressed on a logarithmic scale. The effects on weights of shoots and roots per container were not normally distributed, nor were the effects on the number of plants standing (those which survived). Statements about the effect on the number standing and the shoot weight per container involved using the observed (empirical) distribution. This is illustrated with an example. Problems were encountered in defining the population of species at risk, and in deciding how this population should be formally sampled. The limitations of the method are discussed.     

On the Effects of Capacity Agent on Market Equilibrium

We consider a setting of two firms and one capacity agent. Each firm serves a primary market, and the capacity agent sustains a common market to draw demand for capacity from the external firms. The firms can partner with the capacity agent under her contract to serve the common market. When they use the common market mainly as an outlet for their unused capacities, the capacity agent will only specify a variable fee for each capacity unit deployed through her, and prefer to partner with one firm in most circumstances. When the firms adjust capacities to accommodate the businesses created by serving the common market, the capacity agent will specify a lump‐sum payment and a variable fee, and will be more likely to incentivize only one firm to partner with her, when the common market is sufficiently large or the demands in the common and primary markets are strongly correlated. She will always use a fixed fee to extract, while not necessarily all, the profit gains to the firms serving the common market, but will use a variable fee only when partnering with both firms. The key results are robust with respect to market configuration and contract type.     

Analysis of Regional Scale Risk of Whirling Disease in Populations of Colorado and Rio Grande Cutthroat Trout Using a Bayesian Belief Network Model

Introduction and spread of the parasite Myxobolus cerebralis, the causative agent of whirling disease, has contributed to the collapse of wild trout populations throughout the intermountain west. Of concern is the risk the disease may have on conservation and recovery of native cutthroat trout. We employed a Bayesian belief network to assess probability of whirling disease in Colorado River and Rio Grande cutthroat trout (Oncorhynchus clarkii pleuriticus and Oncorhynchus clarkii virginalis, respectively) within their current ranges in the southwest United States. Available habitat (as defined by gradient and elevation) for intermediate oligochaete worm host, Tubifex tubifex, exerted the greatest influence on the likelihood of infection, yet prevalence of stream barriers also affected the risk outcome. Management areas that had the highest likelihood of infected Colorado River cutthroat trout were in the eastern portion of their range, although the probability of infection was highest for populations in the southern, San Juan subbasin. Rio Grande cutthroat trout had a relatively low likelihood of infection, with populations in the southernmost Pecos management area predicted to be at greatest risk. The Bayesian risk assessment model predicted the likelihood of whirling disease infection from its principal transmission vector, fish movement, and suggested that barriers may be effective in reducing risk of exposure to native trout populations. Data gaps, especially with regard to location of spawning, highlighted the importance in developing monitoring plans that support future risk assessments and adaptive management for subspecies of cutthroat trout.     

Effect of the doctor on college students' attitudes toward physician-assisted suicide

Ninety-six students were presented with eighteen different vignettes describing different types of active and passive observed suicide, assisted suicide, and euthanasia. Attitudes regarding the morality and desired legality of each situation were measured. Results indicated that the interaction between the doctor and the patient, and, to a lesser extent, the active or passive nature of the agent of death, were more important than the actual actions of the doctor in allowing or causing death to occur.     

Chronic stress and chronic disease in life and work: Conceptual and methodological issues

This paper argues that the lack of strong prospective evidence linking occupational and social stress to chronic disease stems from the failure of research designs to attend sufficiently to the aetiological chronicity of such diseases. Studies of both supposedly acute stress (life events) and chronic stress in life or work must increasingly be designed to distinguish between stress which is sustained or chronic over a period of yean or even decades, and hence capable of causing a serious chronic disease, and brief or transient stress, which may produce transient or brief psychological or physiological disturbances but cannot generate major chronic disease. Prospective studies are needed which collect measures of both stress and health or disease at multiple points over an extended period of time. Measures of stress should focus more on affect (for example, feelings of pressure and tension) than on cognition (for example feelings of satisfaction). Limited existing evidence is consistent with these ideals.     

On the Discrete Version of the Aumann–Shapley Cost‐Sharing Method

Each agent in a finite set requests an integer quantity of an idiosyncratic good; the resulting total cost must be shared among the participating agents. The Aumann–Shapley prices are given by the Shapley value of the game where each unit of each good is regarded as a distinct player. The Aumann–Shapley cost‐sharing method charges to an agent the sum of the prices attached to the units she consumes. We show that this method is characterized by the two standard axioms of Additivity and Dummy, and the property of No Merging or Splitting: agents never find it profitable to split or to merge their consumptions. We offer a variant of this result using the No Reshuffling condition: the total cost share paid by a group of agents who consume perfectly substitutable goods depends only on their aggregate consumption. We extend this characterization to the case where agents are allowed to consume bundles of goods.     

No‐Betting‐Pareto Dominance

We argue that the notion of Pareto dominance is not as compelling in the presence of uncertainty as it is under certainty. In particular, voluntary trade based on differences in tastes is commonly accepted as desirable, because tastes cannot be wrong. By contrast, voluntary trade based on incompatible beliefs may indicate that at least one agent entertains mistaken beliefs. We propose and characterize a weaker, No‐Betting, notion of Pareto domination which requires, on top of unanimity of preference, the existence of shared beliefs that can rationalize such preference for each agent.     

Development of an Interspecies Nested Dose‐Response Model for Mycobacterium avium subspecies paratuberculosis

Mycobacterium avium subspecies paratuberculosis (MAP) causes chronic inflammation of the intestines in humans, ruminants, and other species. It is the causative agent of Johne's disease in cattle, and has been implicated as the causative agent of Crohn's disease in humans. To date, no quantitative microbial risk assessment (QMRA) for MAP utilizing a dose‐response function exists. The objective of this study is to develop a nested dose‐response model for infection from oral exposure to MAP utilizing data from the peer‐reviewed literature. Four studies amenable to dose‐response modeling were identified in the literature search and optimized to the one‐parameter exponential or two‐parameter beta‐Poisson dose‐response models. A nesting analysis was performed on all permutations of the candidate data sets to determine the acceptability of pooling data sets across host species. Three of four data sets exhibited goodness of fit to at least one model. All three data sets exhibited good fit to the beta‐Poisson model, and one data set exhibited goodness of fit, and best fit, to the exponential model. Two data sets were successfully nested using the beta‐Poisson model with parameters α = 0.0978 and N₅₀ = 2.70 × 10² CFU. These data sets were derived from sheep and red deer host species, indicating successful interspecies nesting, and demonstrate the highly infective nature of MAP. The nested dose‐response model described should be used for future QMRA research regarding oral exposure to MAP.     

The weighted link ring loading problem

In the weighted link ring loading problem, we are given an n-node undirected ring network. Each of its links is associated with a weight. Traffic demands are given for each pair of nodes in the ring. The load of a link is the sum of the flows routed through the link, and the weighted load of a link is the product of its weight and the smallest integer not less than its load. The objective of the problem is to find a routing scheme such that the maximum weighted load on the ring is minimized. In this paper we consider three variants: (i) demands may be split into two parts, and then each part is sent in a different direction; (ii) demands are allowed to be split into two parts but restricted to be integrally split; (iii) each demand must be entirely routed in either of the two directions, clockwise or counterclockwise. We first prove that the first variant is polynomially solvable. We then present a pseudo-polynomial time algorithm for the second one. Finally, for the third one, whose NP-hardness can be drawn from the result in the literature, we derive a polynomial-time approximation scheme (PTAS).     

Spatial Quantification of the Population Exposed to Cryptococcus neoformans and Cryptococcus gattii Species Complexes in Europe: Estimating the Immunocompetent and HIV/AIDS Patients Under Risk

Cryptococcus is an important fungal pathogen worldwide, causing serious clinical manifestations that can affect immunocompetent patients and can be particularly severe for immunocompromised patients. The Cryptococcus gattii s.s. (AFLP4/VGI), Cryptococcus tetragattii (AFLP/VGIV), Cryptococcus neoformans, and Cryptococcus deneoformans have been isolated from both clinical and environmental sources in Europe. We aim to quantify the people in Europe and the entire Mediterranean area who are under risk associated with each of the three fungal pathogens in a spatially explicit way, generating a series of maps and population statistics per country. Niche modeling was applied to estimate the potential distribution of each fungal pathogen, then these models were overlapped with a map of population density to estimate risk levels. The potential number of people per risk level and per country was quantified using a map of population count per pixel. Prevalence of HIV per country was also included in the analysis to quantify the HIV-infected population under potential risk. People under risk associated with exposure to C. gattii species (C. gattii s.s. and C. tetragattii) reached 137.65 million, whereas those exposed to C. neoformans and C. deneoformans were 268.58 and 360.78 million people, respectively. More than a half million HIV-infected patients are exposed to each of the two species of the C. neoformans species complex, and more than 200,000 to the C. gattii species complex. The present results can be useful for public health planning by European governments, focusing on the provision of inputs for a “screen-and-treat” approach, availability of medical resources, and continuous monitoring programs in risk zones.     

THE IMPACT OF ENTERPRISE INFORMATION TECHNOLOGY ADOPTION ON OPERATIONAL PERFORMANCE: AN EMPIRICAL INVESTIGATION

This paper presents the results of a natural experiment conducted at a U.S. high‐tech manufacturer. The experiment had as its treatment the adoption, at a single point in time, of a comprehensive enterprise information system throughout the functional groups charged with customer order fulfillment. This information technology (it) adoption was not accompanied by substantial contemporaneous business process changes. Immediately after adoption, lead time and on‐time delivery performance suffered, causing a “performance dip” similar to those observed after the introduction of capital equipment onto shop floors. Lead times and on‐time delivery percentages then improved along a learning curve. After several months, performance in these areas improved significantly relative to preadoption levels. These observed performance patterns could not be well explained by rival causal factors such as order, production, and inventory volumes; head count; and new product introductions. Thus, this longitudinal research presents initial evidence of a causal link between IT adoption and subsequent improvement in operational performance measures, as well as evidence of the timescale over which these benefits appear.