Impact of physical handicaps on operators of agricultural equipment

Physically handicapped farm operators and agricultural workers face barriers which make the completion of many essential farm-related tasks difficult or even impossible. These barriers are especially burdensome with respect to the operation and maintenance of agricultural equipment. This paper reports on work being done at Purdue University to assist handicapped farmers and agricultural workers who wish to continue working in spite of their disabilities. The nature of physical handicaps and proportion of farmers affected by these handicaps is discussed. Potential health and safety risks that these operators are exposed to when operating agricultural equipment are addressed. In addition, a brief overview of the Purdue project and recent activities is provided.     

油藏模拟中二维及三维分形分布的比较

分形地质统计学可用于求取孔隙率及渗透率等油藏特性分布。我们比较了油臧模拟中使用这些发布的三种不同方法，第一种混合有发差分／流管法，这种方法由具有相对较密网格的二维垂直横断面入手，第二种方法使用拟相对渗透率曲线，也是基于二维横截面的，第三种方法使用三维分布，本文中我们以一个中后期注水的碳酸盐岩油臧作为油田测试实例。     

Thin film thickness monitor shutter

This article describes a simple electronic dual-activated shutter which is designed to interface with the Sloan digital thickness monitor model DTM-200 or a set of double-pole double-throw switches which can be operated manually.     

Nonlinear optical chromophores as nanoscale emitters for single-molecule spectroscopy

Fluorescence imaging of single molecules at room temperature is a powerful technique for studying complex condensed phase systems and revealing structure and dynamics hidden by ensemble measurements. Successful single-molecule spectroscopic experiments rely upon strong emitters that can be detected at the level of individual copies above the relevant background signals. This Account discusses a class of nonlinear optical chromophores that not only are well-suited for single-molecule imaging but also offer additional beneficial properties such as a significant ground-state dipole moment, moderate hyperpolarizability, and sensitivity to local environment. An overview of the photophysical properties of several members of this class of molecules as well as a mechanism to help understand the environmental sensitivity is presented. Some preliminary applications of the chromophores as single-molecule reporters in cellular and polymer systems are discussed, along with detection of the emitters by two-photon fluorescence.     

Biosynthesis of phospholipids in subcellular particles from cultured cells of human tissue

A time study of the incorporation of³²P_i into the phospholipids of HeLa, KB, human heart, and liver tissue-culture cell lines has been carried out. The incorporation of³²P_i at various time-intervals into the phospholipids of nuclei, mitochondria, and microsomes of HeLa and KB cells was investigated. The labeling of the isotope into the phospholipids was divided into three groups. The first had two components: phosphatidyl inositol and polyglycerol phosphatides, which showed the greatest incorporation of the isotope as demonstrated in the specific activity values and the percentage of total radioactivity after 15 to 30 minutes of incubation. A second group was composed of the major phospholipids of all tissue-culture cell lines studied, phosphatidyl choline, and phosphatidyl ethanolamine. At first, there was a delayed labeling of these phospholipids; however, after one hour of incubation, a rapid increase was shown in the incorporation of³²P_i. A third group of lipids containing sphingomyelin and phosphatidyl serine demonstrated low specific activity values. The phospholipids of the subcellular fractions, nuclei, mitochondria, and microsomes, had a high degree of incorporation of the isotope into the individual phospholipids and probably represented an active process in the membranes of these cellular units or a renewal of the biological membrane structures. Part of a thesis submitted to the Graduate School of the University of North Dakota in partial fulfillment for the degree of Doctor of Philosophy.     

Thermal conductivity of boron carbide under fast neutron irradiation

Due to the complex products and irradiation-induced defects, it is hard to understand and even predict the thermal conductivity variation of materials under fast neutron irradiation, such as the abrupt degradation of thermal conductivity of boron carbide (B₄C) at the very beginning of the irradiation process. In this work, the contributions of various irradiation-induced defects in B₄C primarily consisting of the substitutional defects, Frenkel defect pairs, and helium bubbles were re-evaluated separately and quantitatively in terms of the phonon scattering theory. A theoretical model with an overall consideration of the contributions of all these irradiation-induced defects was proposed without any adjustable parameters, and validated to predict the thermal conductivity variation under irradiation based on the experimental data of the unirradiated, irradiated, and annealed B₄C samples. The predicted thermal conductivities by this model show a good agreement with the experimental data after irradiation. The calculation results and theoretical analysis in light of the experimental data demonstrate that the substitutional defects of boron atoms by lithium atoms, and the Frenkel defect pairs due to the collisions with the fast neutrons, rather than the helium bubbles with strain fields surrounding them, play determining roles in the abrupt degradation of thermal conductivity with burnup.     

Risk factors associated with selected indicators of milk quality in semiarid northeastern Brazil

The aim of this study was to gain information on quality traits, mainly bacterial and somatic cell counts of bulk milk, produced by small- and medium-scale producers in a semiarid northeastern region of Brazil and to identify and characterize possible risk factors associated with those quality traits. A cross-sectional study was performed on 50 farms. Bulk milk samples were collected for bacterial and somatic cell counts. Additionally, information about farm demographics, general management practices, hygiene, and milking procedures was also obtained. Multivariable analysis using logistic regression was performed with predictors previously identified by univariate analysis using a Fisher's Exact test. Aerobic mesophilic bacteria counts varied from 3.59 log to 6.95 log cfu/mL, with geometric mean of 5.27 log cfu/mL. Mean total coliform count was 3.27 log (1.52 log to 5.89 log) most probable number (MPN)/mL, whereas mean thermotolerant coliforms was 2.38 log (1.48 log to 4.75 log) MPN/mL. A high positive correlation was observed between aerobic mesophilic bacteria and coliform counts. Although most farms met the standard for the current regulations for total bacteria (88%) and somatic cell counts (94%), nearly half of the producers (46%) would have problems in achieving the 2012 threshold limit for total bacteria count if no improvement in milk quality occurs. Mean value for staphylococci was 3.99 log (2.31 log to 6.24 log) cfu/mL, and Staphylococcus aureus was detected in 33 (66%) farms. Premilking teat-end wash procedure (odds ratio = 0.191) and postmilking teat dip (odds ratio = 0.67) were associated with lower aerobic mesophilic bacteria and Staphylococcus aureus counts in bulk milk, respectively. Considering that the farm characteristics in this study are representative of the semiarid northeastern region, these findings encourage further investigations for supporting intervention measures intended to improve the quality of milk produced by smallholders.     

Spatial variability of fine particle mass, components, and source contributions during the regional air pollution study in St. Louis

Community time-series epidemiology typically uses either 24-hour integrated particulate matter (PM) concentrations averaged across several monitors in a city or data obtained at a central monitoring site to relate PM concentrations to human health effects. If the day-to-day variations in 24-hour integrated concentrations differ substantially across an urban area (i.e., daily measurements at monitors at different locations are not highly correlated), then there is a significant potential for exposure misclassification in community time-series epidemiology. If the annual average concentration differs across an urban area, then there is a potential for exposure misclassification in epidemiologic studies that use annual averages (or multi-year averages) as an index of exposure across different cities. The spatial variability in PM2.5 (particulate matter < or = 2.5 microm in aerodynamic diameter), its elemental components, and the contributions from each source category at 10 monitoring sites in St. Louis, Missouri were characterized using the ambient PM2.5 compositional data set of the Regional Air Pollution Study (RAPS) based on the Regional Air Monitoring System (RAMS) conducted between 1975 and 1977. Positive matrix factorization (PMF) was applied to each ambient PM2.5 compositional data set to estimate the contributions from the source categories. The spatial distributions of components and source contributions to PM2.5 at the 10 sites were characterized using Pearson correlation coefficients and coefficients of divergence. Sulfur and PM2.5 are highly correlated elements between all of the site pairs Although the secondary sulfate is the most highly correlated and shows the smallest spatial variability, there is a factor of 1.7 difference in secondary sulfate contributions between the highest and lowest site on average. Motor vehicles represent the next most highly correlated source component. However, there is a factor of 3.6 difference in motor vehicle contributions between the highest and lowest sites. The contributions from point source categories are much more variable. For example, the contributions from incinerators show a difference of a factor of 12.5 between the sites with the lowest and highest contributions. This study demonstrates that the spatial distributions of elemental components of PM2.5 and contributions from source categories can be highly heterogeneous within a given airshed and thus, there is the potential for exposure misclassification when a limited number of ambient PM monitors are used to represent population-average ambient exposures.     

Levels of polybrominated diphenyl ether (PBDE) flame retardants in animals representing different trophic levels of the North Sea food Web

The levels of individual PBDE congeners were investigated in the invertebrate species whelk (Buccinum undatum), seastar (Asterias rubens), and hermit crab (Pagurus bernhardus), the gadoid fish species whiting (Merlangius merlangus) and cod (Gadus morhua), and the marine mammal species harbor seal (Phoca vitulina) and harbor porpoise (Phocoena phocoena). These species are all important representatives of different trophic levels of the North Sea food web. All six major PBDE congeners detected (BDEs 28, 47, 99, 100, 153, and 154) are most prevalent in the commercial Penta-BDE formulation. There is no evidence for the occurrence of the Octa-BDE formulation in the North Sea food web, since its dominant congener, BDE183, was never detected. BDE209, the main congener (> 97%) in the Deca-BDE formulation, was detected only in a minority of the samples and always in concentrations around the limit of detection. Since BDE209 is often the major BDE congener in sediments from the area, the main reason for its low concentrations in biota from the North Sea seems to be a relatively low bioaccumulation potential. This can either be due to a low uptake rate of the very large molecule or a relatively rapid excretion after biotransformation. Since all invertebrates investigated are sentinel species, they are highly representative for the area of capture. The highest lipid-normalized concentrations of PBDEs in the invertebrates occurred near the mouth of the river Tees at the East coast of the UK. The geographical distribution of the PBDEs can be explained by the residual currents in the area. The direction of these currents differs between the summer and the winter season as a result of the presence or absence of vertical summer stratification of the deeper waters north of the Dogger Bank. Summer stratification results in the development of a density-driven bottom water current formed after the onset of vertical stratification of the water column in May leaving the UK coast near Flamborough Head toward the Dogger Bank. In winter, the residual currents run in a more southerly direction and follow the UK coastline. The distribution pattern of the PCBs and p,p'-DDE in the invertebrates was entirely different from that of the PBDEs, which could be expected, since the use of these organochlorines in western Europe peaked in the 1960s and 1970s but has been forbidden more than two decades ago, whereas the production and use of the penta-BDE formulation is of a more recent origin. The higher trophic levels of the North Sea food web were represented by the predatory gadoid fish species whiting and cod and the marine mammal species harbor seal and harbor porpoise. The lipid-normalized levels of the six major PBDE congeners in fish were similar to the levels in the invertebrates, but a biomagnification step in concentrations of generally more than an order of magnitude occurred from gadoid fish to marine mammals. Based on the limited number of samples, no differences could be observed between harbor seal and harbor porpoise. In summary, the results in three species of sentinel invertebrates from a network of stations covering a major part of the North Sea basin showed that the estuary of the river Tees at the UK East coast is a major source for tri- to hexa-PBDEs. Throughout the food-chain, the most marked increase in (lipid-normalized) levels of all six PBDE congeners occurred from predatory (gadoid) fish to marine mammals, agreeing with the transition from gill-breathing to lung-breathing animals. This has serious consequences for the route of elimination of POPs, since their elimination from the blood into the ambient seawater via the gill-membrane is no longer possible.