The power of inequality semijoins

Semijoin is a relational operator used in many relational query processing algorithms. Semijoins can be used to “reduce” the database by delimitting portions of the database that contain data relevant to a given query. For some queries, there exist sequences of semijoins that delimit the exact portions of the database needed to answer the query. Such sequences are called full reducers.

This paper considers a class of queries called natural inequality queries (NI queries), and characterizes a subclass for which full reducers exist. We also present an efficient algorithm that decides whether an NI query lies within this subclass, and constructs a full reducer for the query. The NI queries are a subset of the aggregate-free, conjunctive queries of QUEL, and permit join clauses to include <, , =, , >.     

Leukocyte image analysis in the diff3 system

The diff3 System uses image processing and pattern recognition techniques to automatically analyze normal and abnormal white blood cells in a blood smear. The system consists of a spinner which creates a monolayer of cells on a glass slide, a stainer utilizing Wright's stain, the reagents to support the spinner and stainer, and an analyzer for automatic slide handling, analysis and report generation. The analyzer incorporates a wide range of image processing functions, including the generation and storage of gray scale image data, whole-field and partial-field image histogramming, and high-order binary image texture analysis and image transformation using the Golay processor (GLOPR). This paper describes the manner in which these hardware capabilities are used for white cell acquisition, scene segmentation and feature analysis. It concludes with some examples of texture extraction which illustrate the power of the Golay processor as a tool for image analysis.     

Zero Risk Does Not Exist: Lessons Learned from Microbial Risk Assessment Related to Use of Water and Safety of Fresh Produce

Risk assessments related to use of water and safety of fresh produce originate from both water and food microbiology studies. Although the set‐up and methodology of risk assessment in these 2 disciplines may differ, analysis of the current literature reveals some common outcomes. Most of these studies from the water perspective focus on enteric virus risks, largely because of their anticipated high concentrations in untreated wastewater and their resistance to common wastewater treatments. Risk assessment studies from the food perspective, instead, focus mainly on bacterial pathogens such as Salmonella and pathogenic Escherichia coli. Few site‐specific data points were available for most of these microbial risk assessments, meaning that many assumptions were necessary, which are repeated in many studies. Specific parameters lacking hard data included rates of pathogen transfer from irrigation water to crops, pathogen penetration, and survival in or on food crops. Data on these factors have been investigated over the last decade and this should improve the reliability of future microbial risk estimates. However, the sheer number of different foodstuffs and pathogens, combined with water sources and irrigation practices, means that developing risk models that can span the breadth of fresh produce safety will be a considerable challenge. The new approach using microbial risk assessment is objective and evidence‐based and leads to more flexibility and enables more tailored risk management practices and guidelines. Drawbacks are, however, capacity and knowledge to perform the microbial risk assessment and the need for data and preferably data of the specific region.     

Experimental test of the valence-instrumentality relationship in job performance.

Tested expectancy-valence models of work motivation which postulate an interactive relationship between valence of outcomes and performance-outcome instrumentality. Ss were 60 college-age respondents to an ad for part-time clerical work. Valence of job outcomes was set at 2 levels (high and low) by establishing 2 different pay rates; performance-outcome instrumentality was determined by paying wages hourly (low instrumentality) or by the piece (high instrumentality). It was hypothesized that these variables would combine interactively to affect task performance and effort. While main effects for both performance-outcome instrumentality and valence of job outcomes were observed, the predicted interaction did not appear. Results suggest that the typical conceptualization of valence as the importance an individual attaches to an outcome may be inappropriate. (19 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Chemical loading into surface water along a hydrological, biogeochemical, and land use gradient: a holistic watershed approach

Identifying the sources and impacts of organic and inorganic contaminants at the watershed scale is a complex challenge because of the multitude of processes occurring in time and space. Investigation of geochemical transformations requires a systematic evaluation of hydrologic, landscape, and anthropogenic factors. The 1160 km2 Boulder Creek Watershed in the Colorado Front Range encompasses a gradient of geology, ecotypes, climate, and urbanization. Streamflow originates primarily as snowmelt and shows substantial annual variation. Water samples were collected along a 70-km transect during spring-runoff and base-flow conditions, and analyzed for major elements, trace elements, bulk organics, organic wastewater contaminants (OWCs), and pesticides. Major-element and trace-element concentrations were low in the headwaters, increased through the urban corridor, and had a step increase downstream from the first major wastewater treatment plant (WWTP). Boron, gadolinium, and lithium were useful inorganic tracers of anthropogenic inputs. Effluent from the WWTP accounted for as much as 75% of the flow in Boulder Creek and was the largest chemical input. Under both hydrological conditions, OWCs and pesticides were detected in Boulder Creek downstream from the WWTP outfall as well as in the headwater region, and loads of anthropogenic-derived contaminants increased as basin population density increased. This report documents a suite of potential endocrine-disrupting chemicals in a reach of stream with native fish populations showing indication of endocrine disruption.     

Organic carbon-water concentration quotients (II(SOC)S and pi(poc)S): measuring apparent chemical disequilibria and exploring the impact of black carbon in Lake Michigan

Chemical concentration quotients measured between water and total organic carbon (TOC) in sediment (II(SOC)) or suspended particulates (pi(poc)) in southern Lake Michigan reveal up to 2 orders of magnitude differences for polychlorinated biphenyl (PCB), dibenzo-p-dioxin (PCDD), dibenzofuran (PCDF), and polycyclic aromatic hydrocarbon (PAH) compounds with similar octanol-water partition coefficients (K(ow)S). Apparent disequilibria for PAHs, PCDDs, and PCDFs, determined as measured II(SOC)S or pi(poc)S divided by their organic carbon equilibrium partitioning values, are significantly greater than disequilibria of PCBs with similar K(ow)S. Apparent disequilibria, when adjusted for black carbon content by using published black carbon nonlinear partition coefficients (K(f,bc)S) and a Freundlich exponent (n(f)) value = 0.7, still exceed equilibrium predictions for the PAHs, PCBs, and PCDDs but with the PCDF disequilibria uniquely below equilibrium. While Monte Carlo analysis of all the variables associated with the black carbon adjusted disequilibria provides wide confidence intervals for individual chemicals, the large class disequilibria differences between PAHs and PCDFs with respect to the PCBs and PCDDs are highly significant. Use of the PCDD K(f,bc)S for calculating both the PCDF and PCDD disequilibria eliminates their extreme divergence. On the basis of the complexity of carbonaceous geosorbent effects and the apparent variable degrees of chemical sequestration in particles, the disequilibria can be adjusted by chemical class to meet expected near equilibrium conditions between suspended particles and water in the hypolimnion. Although these adjustments to the disequilibria calculations produce consistent and plausible values, the complexities of variable carbonaceous geosorbent affinities for these chemicals in Lake Michigan presently favor use of measured, rather than a priori modeled, steady-state total organic carbon-water concentration quotients indexed to TOC as biogenic organic carbon.     

碳水化合物——蛋白质饮料对运动耐力的影响

人在长时间运动后的疲劳和体内存储的肌糖原的消耗密切相关,因此运动后糖原合成的速度是短时间内运动恢复的关键因素。接下来的实验有效地研究了运动后补充的营养成分对于再次运动时耐力表现的影响。