Sectors of activity, topography, and parasitism in home areas of New Guinea coarse-haired rats, and Trombiculidae (Acarina)

Summary Home areas of hosts are, in effect the gardens in which parasite populations grow. The parasites flourish in response to the kind and amount of host activity modified, of course, by the habitat, and become microcommunities supported by their host and its artifacts. When scatter diagrams of points at which hosts have been observed are divided by median major and minor axes, and when the resulting four quarters, designated A, B, C, D, corresponding to concentration of points in the quarters, the relative concentration usually is: A>B>C>D. The concentration of observed points also is generally greatest nearest the major axis and frequently, but not always, near the median center. Nests of hosts, hence nest-parasites, appear generally to be near the center. For the host examined in detail here, the New Guinea coarse-haired rat, mostLeptotrombidium deliensis appear to have been acquired in the AB sector of the host's home areas but a greater diversity of chiggers is acquired in the CD sector. It is postulated that, ifL. akamushi had been present, it would have occurred in the CD sector where, though the observed concentration of host activity was least, the mixed grassforb and shrub habitat would have been more suitable than in the AB sector.Gahrliepia pingue, C. ewingi, Schoengastia blestowei andS. schueffneri, appear also to be more abundant in the CD sector than in the AB sector. The chiggers themselves have home clusters, or lairs, and adjacent areas of activity (home areas) somewhat resembling those of the hosts. This analysis of sectors of home areas was begun in 1965 under provision of a research grant (AI-03653) by the National Institutes of Health to the Division of Parasitology, University of California at Berkeley. It was completed during 1967.     

Improving predictive accuracy of logistic regression model using ranked set samples

Logistic regression is often confronted with separation of likelihood problem, especially with unbalanced success–failure distribution. We propose to address this issue by drawing a ranked set sample (RSS). Simulation studies illustrated the advantages of logistic regression models fitted with RSS samples with small sample size regardless of the distribution of the binary response. As sample size increases, RSS eventually becomes comparable to SRS, but still has the advantage over SRS in mitigating the problem of separation of likelihood. Even in the presence of ranking errors, models from RSS samples yield higher predictive ability than its SRS counterpart.     

请再说一遍“我爱你”

【正】请说了一遍,再向我说一遍,说我爱你即使那样一遍遍重复,你会把它看成一支布谷鸟的歌曲;可是记着,在那青山和绿林间,那山谷和田野中,纵使清新的春天披着全身绿装降临、也不算完美无缺,要是她缺少了那串布谷鸟的音节。爱,四周那么黑暗,耳边只听见惊悸的心声,处于那痛苦的不安中,我嚷道:再说一遍:我爱你!谁嫌太多的...     

Choosing the Right Expert System Building Approach

The analytical hierarchy process (AHP) is used to systematically examine the relative appropriateness of contending expert system building approaches—algorithmic programming languages, symbolic programming languages, expert system shells, and knowledge engineering environments based upon characteristics of application domains and development environments. Two expert system projects, Back Expert, and R&D Expert, illustrate the value of this methodology. Domain and development environment characteristics identified in the AHP approach are then used to construct rule-based and Lotus 1-2-3 expert systems for selecting the right expert system building approach.     

Modeling Take-or-Pay Contract Decisions

Long-term purchase contracts for natural resources, such as natural gas, often contain take-or-pay provisions that penalize the buyer for not purchasing (taking) a minimum quantity of output over some period of time. In some contracts for a limited time interval, known as the make-up period, the penalty payments can be credited against future “takes” in excess of the take-or-pay level. Additionally, options to “buy down” or “buy out” existing contracts, or to initiate new contracts, may exist. The purchaser, faced with projected requirements over some planning horizon, must determine purchase levels from a selected set of take-or-pay contracts so as to minimize purchase, inventory holding, penalty costs, contract initiation, and buy-out or buy-down costs. This paper presents a mixed-integer programming model of take-or-pay decisions with and without make-up provisions.     

Permanent Disadvantage or Gradual Integration: Explaining the Immigrant–Native Earnings Gap in Sweden

Theoretical explanations suggest that wage differentials between immigrant and native workers are generated either by differences in the acquisition of human capital or by various forms of exclusion of immigrants from fair labour market rewards. We evaluate the labour quality and labour market discrimination hypotheses by using a large sample of Swedish employees in 1995. Our findings show that labour market integration is relatively unproblematic for immigrants from Western countries, whereas immigrants from other countries, especially from Africa, Asia and Latin America, face substantial obstacles to earnings progress when entering the Swedish labour market. For the latter group of countries, extensive controls for general and country‐specific human capital reduce the earnings differentials. However, the remaining gap is of a non‐trivial magnitude. Thus, the labour quality hypothesis accounts for a part of the observed native–immigrant wage gap, but the remaining differentials can be interpreted in terms of labour market discrimination.