Hampshire College

About: Hampshire College is a education organization based out in Amherst Center, Massachusetts, United States. It is known for research contribution in the topics: Genetic programming & Population. The organization has 461 authors who have published 998 publications receiving 40827 citations.

Biomonitoring of lead in Antarctic lichens using laser ablation inductively coupled plasma mass spectrometry

Abstract: A method for direct determination of Pb by LA-ICP-MS in lichen samples collected in a heavily anthropogenically impacted area of Maritime Antarctica was developed. The lichen samples were cryogenically ground and digested with nitric acid and hydrogen peroxide. Lead determination by solution-based ICP-MS was validated by the use of 2 certified reference materials. Once the Pb concentrations were measured with adequate accuracy and precision, a method for its direct determination by LA-ICP-MS was developed. The laser ablation parameters were optimized by the use of a Doehlert design matrix. The final optimized conditions were: laser energy (60%), spot size (150 μm) and repetition rate (10 Hz). Lead concentration of the analyzed lichen samples were plotted against the intensity of the lead isotopes (208Pb, 207Pb and 206Pb) determined by LA-ICP-MS. Satisfactory linear correlation factors were obtained when 13C was used as internal standard. Lead distribution profiles in lichen thalli cross-sections were also obtained. By these results, LA-ICP-MS emerges as a potential analytical tool for Pb concentration estimation in lichen samples. Minimum amount of sample required, bioimaging capability, high analytical throughput, and minimization of waste generation are the major analytical features of this approach. The significant differences between the Pb concentration in the lichen samples from the control site (1.12 ± 0.05 mg kg−1) and from the impacted points (mean = 5.03 ± 0.57 mg kg−1) permitted qualify these organisms as good biomonitors. Elemental bioimaging of lichens demonstrated that the medulla region of lichen thalli is consistently the main atmospheric lead bioaccumulating lichen tissue.

Ecosystem Structure Emerges as a Strong Determinant of Food-Chain Length in Linked Stream–Riparian Ecosystems

Abstract: Environmental determinants of fluvial food-chain length (FCL) remain unresolved, with predominant hypotheses pointing to productivity, disturbance, and/or ecosystem size. However, drainage configuration (for example, drainage density, and stream length)—in spite of recent advances demonstrating the significance of catchment structure to habitat and biodiversity of fluvial systems—has yet to be explored in relation to FCL. In this study, we quantified the relative influences of ecosystem size and structure on FCL for linked stream‐riparian food webs. At 19 stream reaches distributed within three mountain catchments of northern Idaho, USA, we sampled aquatic and riparian consumers and determined FCL using the naturally abundant stable isotopes 13 Ca nd 15 N. Food-chain length was approach. Model selection was followed by exploratory linear regression of FCL with purported mechanistic factors (that is, resource availability and disturbance regime). FCL ranged from 2.6 to 4.4 across study reaches and was best explained by catchment structure such as number of tributary junctions and distance to nearest downstream confluence. Regression analyses suggested that disturbance regime may mechanistically link number of tributary junctions and FCL, as well as drainage area and FCL. Our results introduce novel evidence that ecosystem structure may integrate the effects of several mechanistic factors and thus be an important predictor of food-web structure.

Report on Performance Results in the NIST 2010 Speaker Recognition Evaluation.

Abstract: In the spring of 2010, the National Institute of Standards and Technology organized a Speaker Recognition Evaluation in which several factors believed to affect the performance of speaker recognition systems were explored. Among the factors considered in the evaluation were channel conditions, duration of training and test segments, number of training segments, and level of vocal effort. New cost function parameters emphasizing lower false alarm rates were used for two of the tests in the evaluation, and the reduction in false alarm rates exhibited by many of the systems suggests that the new measure may have helped to focus research on the low false alarm region of operation, which is important in many applications.

Population Control I: Birth of an Ideology

Abstract: Population control, as a major international development strategy, is a relatively recent phenomenon. However, its origins reach back to social currents in the 19th and early 20th centuries, culminating in an organized birth control movement in Europe and the United States. The conflicts and contradictions in that movement's history presage many of today's debates over population policy and women's rights. Eugenics had a deep influence on the U.S. birth control movement in the first half of the 20th century. After World War II private agencies and foundations played an important role in legitimizing population control as a way to secure Western control over Third World resources and stem political instability. In the late 1960s the U.S. government became a major funder of population control programs overseas and built multilateral support through establishment of the U.N. Fund for Population Activities. At the 1974 World Population Conference, Third World governments challenged the primacy of population c...

Multi-type, Self-adaptive Genetic Programming as an Agent Creation Tool

Abstract: This paper describes the application of multitype, self-adaptive genetic programming techniques, implemented in the PushGP and Pushpop systems, to the automatic programming of multi-agent systems. It includes a brief case study of the application of PushGP to a transport network control problem and a demonstration of self-adaptive modularization in a dynamic environment that was developed by Van Belle and Ackley.