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Operations in the iron and steel industry generate and potentially expose employees to airborne particulates not otherwise classifiable (PNOC) which may contain various forms of silica that have been implicated for respiratory diseases. This study assessed occupational exposure to PNOC fractions (PM5, PM10) and compliance to national occupational exposure limits (OEL) in five workstations at an iron and steel industry. Personal dust samples were collected using standard procedures in three 2hour periods of an 8hour work shift and gravimetrically analysed to estimate time-weighted averages. The highest mean concentrations of PNOC for PM5 (0.65±0.29mg/m3) and PM10 (2.88±0.97mg/m3) recorded for employees at the Box Vibrator in the foundry were significantly lower than the national OELs for PNOC for both PM5 (5mg/m3) and PM10 (10mg/m3) (p<0.05). So were the least concentrations of PNOC for both PM5 (0.004±0.001mg/m3) and PM10 (0.71±0.38mg/m3) recorded at the Administration (p<0.05). Employees across all the five workstations were not exposed to significantly high concentrations of PNOC when compared to national OELs (p<0.05). However, the health risk associated to occupational exposure levels of employees can only be ascertained when specific components of the respirable PNOC are estimated. The concentrations of PNOC fractions to which employees were exposed to were generally a function of distance from the source. [ABSTRACT FROM AUTHOR]

Twenty years ago, the landmark AM1 was introduced, and has since had an increasingly wide following among chemists due to its consistently good results and time-tested reliability—being presently available in countless computational quantum chemistry programs. However, semiempirical molecular orbital models still are of limited accuracy and need to be improved if the full potential of new linear scaling techniques, such as MOZYME and LocalSCF, is to be realized. Accordingly, in this article we present RM1 (Recife Model 1): a reparameterization of AM1. As before, the properties used in the parameterization procedure were: heats of formation, dipole moments, ionization potentials and geometric variables (bond lengths and angles). Considering that the vast majority of molecules of importance to life can be assembled by using only six elements: C, H, N, O, P, and S, and that by adding the halogens we can now build most molecules of importance to pharmaceutical research, our training set consisted of 1736 molecules, representative of organic and biochemistry, containing C, H, N, O, P, S, F, Cl, Br, and I atoms. Unlike AM1, and similar to PM3, all RM1 parameters have been optimized. For enthalpies of formation, dipole moments, ionization potentials, and interatomic distances, the average errors in RM1, for the 1736 molecules, are less than those for AM1, PM3, and PM5. Indeed, the average errors in kcal · mol-1 of the enthalpies of formation for AM1, PM3, and PM5 are 11.15, 7.98, and 6.03, whereas for RM1 this value is 5.77. The errors, in Debye, of the dipole moments for AM1, PM3, PM5, and RM1 are, respectively, 0.37, 0.38, 0.50, and 0.34. Likewise, the respective errors for the ionization potentials, in eV, are 0.60, 0.55, 0.48, and 0.45, and the respective errors, in angstroms, for the interatomic distances are 0.036, 0.029, 0.037, and 0.027. The RM1 average error in bond angles of 6.82° is only slightly higher than the AM1 figure of 5.88°, and both are much smaller than the PM3 and PM5 figures of 6.98° and 9.83°, respectively. Moreover, a known error in PM3 nitrogen charges is corrected in RM1. Therefore, RM1 represents an improvement over AM1 and its similar successor PM3, and is probably very competitive with PM5, which is a somewhat different model, and not fully disclosed. RM1 possesses the same analytical construct and the same number of parameters for each atom as AM1, and, therefore, can be easily implemented in any software that already has AM1, not requiring any change in any line of code, with the sole exception of the values of the parameters themselves. © 2006 Wiley Periodicals, Inc. J Comput Chem 27: 1101–1111, 2006 [ABSTRACT FROM AUTHOR]

Nodals are signaling factors of the transforming growth factor-ß (TGFß) superfamily with a key role in vertebrate development. They control a variety of cell fate decisions required for the establishment of the embryonic body plan. We have identified two highly conserved transmembrane proteins, Nicalin and Nomo (Nodal modulator, previously known as pM5), as novel antagonists of Nodal signaling. Nicalin is distantly related to Nicastrin, a component of the Alzheimer's disease-associated ?-secretase, and forms a complex with Nomo. Ectopic expression of both proteins in zebrafish embryos causes cyclopia, a phenotype that can arise from a defect in mesendoderm patterning mediated by the Nodal signaling pathway. Accordingly, downregulation of Nomo resulted in an increase in anterior axial mesendoderm and the development of an enlarged hatching gland. Inhibition of Nodal signaling by ectopic expression of Lefty was rescued by reducing Nomo levels. Furthermore, Nodal- as well as Activin-induced signaling was inhibited by Nicalin and Nomo in a cell-based reporter assay. Our data demonstrate that the Nicalin/Nomo complex antagonizes Nodal signaling during mesendodermal patterning in zebrafish. [ABSTRACT FROM AUTHOR]