The ubiquity and durability of lithic artifacts inform archaeologists about important dimensions of human behavioral variability. Despite their importance, lithic artifacts can be problematic to study because lithic analysts differ widely in their theoretical approaches and the data they collect. The extent to which differences in lithic data relate to prehistoric behavioral variability or differences between archaeologists today remains incompletely known. We address this issue with the most extensive lithic replicability study yet, involving 11 analysts, 100 unmodified flakes, and 38 ratio, discrete, and nominal attributes. We use mixture models to show strong inter-analyst replicability scores on several attributes, making them well suited to comparative lithic analyses. Based on our results, we highlight 17 attributes that we consider reliable for compiling datasets collected by different individuals for comparative studies. Demonstrating this replicability is a crucial first step in tackling more general problems of data comparability in lithic analysis and lithic analyst's ability to conduct large-scale meta-analyses.

Objectives: This study aimed to evaluate the influence of lower limb loss (LL) on mental workload by assessing neurocognitive measures in individuals with unilateral transtibial (TT) versus those with transfemoral (TF) LL while dual-task walking under varying cognitive demand. Methods: Electroencephalography (EEG) was recorded as participants performed a task of varying cognitive demand while being seated or walking (i.e., varying physical demand). Results: The findings revealed both groups of participants (TT LL vs. TF LL) exhibited a similar EEG theta synchrony response as either the cognitive or the physical demand increased. Also, while individuals with TT LL maintained similar performance on the cognitive task during seated and walking conditions, those with TF LL exhibited performance decrements (slower response times) on the cognitive task during the walking in comparison to the seated conditions. Furthermore, those with TF LL neither exhibited regional differences in EEG low-alpha power while walking, nor EEG high-alpha desynchrony as a function of cognitive task difficulty while walking. This lack of alpha modulation coincided with no elevation of theta/alpha ratio power as a function of cognitive task difficulty in the TF LL group. Conclusions: This work suggests that both groups share some common but also different neurocognitive features during dual-task walking. Although all participants were able to recruit neural mechanisms critical for the maintenance of cognitive-motor performance under elevated cognitive or physical demands, the observed differences indicate that walking with a prosthesis, while concurrently performing a cognitive task, imposes additional cognitive demand in individuals with more proximal levels of amputation.

A segment of the debate surrounding the commercialization of geneticallyengineered (GE) crops, such as glyphosate-resistant (GR) crops, focuses onthe theory that implementation of these traits is an extension of theintensification of agriculture that will further erode the biodiversity ofagricultural landscapes. A large field-scale study was conducted in 2006 inthe United States on 156 different field sites with a minimum 3-yr historyof GR corn, cotton, or soybean in the cropping system. The impact ofcropping system, crop rotation, frequency of using the GR crop trait, andseveral categorical variables on emerged weed density and diversity wasanalyzed. Species richness, evenness, Shannon's H′, proportion of forbs,erect growth habit, and C3 species diversity were all greater inagricultural sites that lacked crop rotation or were in a continuous GR cropsystem. Rotating between two GR crops (e.g., corn and soybean) or rotatingto a non-GR crop resulted in less weed diversity than a continuous GR crop.The composition of the weed flora was more strongly related to location(geography) than any other parameter. The diversity of weed flora inagricultural sites with a history of GR crop production can be influenced byseveral factors relating to the specific method in which the GR trait isintegrated (cropping system, crop rotation, GR trait rotation), the specificweed species, and the geographical location. The finding that fields withcontinuous GR crops demonstrated greater weed diversity is contrary toarguments opposing the use of GE crops. These results justify furtherresearch to clarify the complexities of crops grown withherbicide-resistance traits, or more broadly, GE crops, to provide a morecomplete characterization of their culture and local adaptation.

A segment of the debate surrounding the commercialization and use of glyphosate-resistant (GR) crops focuses on the theory that the implementation of these traits is an extension of the intensification of agriculture that will further erode the biodiversity of agricultural landscapes. A large field-scale study was initiated in 2006 in the United States on 156 different field sites with a minimum 3-yr history of GR-corn, -cotton or -soybean in the cropping system. The impact of cropping system, crop rotation, frequency of using the GR crop trait, and several categorical variables on seedbank weed population density and diversity was analyzed. The parameters of total weed population density of all species in the seedbank, species richness, Shannon's H′ and evenness were not affected by any management treatment. The similarity between the seedbank and aboveground weed community was more strongly related to location than management; previous year's crops and cropping systems were also important while GR trait rotation was not. The composition of the weed flora was more strongly related to location (geography) than any other parameter. The diversity of weed flora in agricultural sites with a history of GR crop production can be influenced by several factors relating to the specific method in which the GR trait is integrated (cropping system, crop rotation, GR trait rotation), the specific weed species, and the geographical location. Continuous GR crop, compared to fields with other cropping systems, only had greater species diversity (species richness) of some life forms, i.e., biennials, winter annuals, and prostrate weeds. Overall diversity was related to geography and not cropping system. These results justify further research to clarify the complexities of crops grown with herbicide-resistance traits to provide a more complete characterization of their culture and local adaptation to the weed seedbank.

Darwinism is a principle of biological continuity. This commentary argues against any claim of discontinuity between humans and other animals that must be based on absence of evidence. Instead, we offer additional examples of active teaching by chimpanzees.

Nested data-parallelism (NDP) is a language mechanism that supports programming irregular parallel applications in a declarative style. In this paper, we describe the implementation of NDP in Parallel ML (PML), which is a part of the Manticore system. One of the main challenges of implementing NDP is managing the parallel decomposition of work. If we have too many small chunks of work, the overhead will be too high, but if we do not have enough chunks of work, processors will be idle. Recently, the technique of Lazy Binary Splitting was proposed to address this problem for nested parallel loops over flat arrays. We have adapted this technique to our implementation of NDP, which uses binary trees to represent parallel arrays. This new technique, which we call Lazy Tree Splitting (LTS), has the key advantage of performance robustness, i.e., it does not require tuning to get the best performance for each program. We describe the implementation of the standard NDP operations using LTS and present experimental data that demonstrate the scalability of LTS across a range of benchmarks.