Little is known about the physicochemical properties of beryllium aerosols associated with increased risk of beryllium sensitization and chronic beryllium disease (CBD). Such information is needed to ...evaluate whether airborne mass of beryllium is the appropriate metric of exposure or alternatively to provide a scientific basis for using information on particle size, surface area, and chemistry to support an improved exposure limit based on bioavailability through the inhalation and dermal routes of exposure. Thus, we used a suite of analytical techniques to characterize aerodynamically size-fractionated beryllium particles and powders that have been associated in epidemiological studies with higher prevalence of CBD. Aerosol particles were sampled from the ventilation systems of production lines for powders of beryllium metal and beryllium oxide and for ingots of copper-beryllium alloy. End product powders from the metal and oxide production lines were also collected. Particles released during production of beryllium metal were found to be complex, having heterogeneous composition, including reactive species such as fluorine. Powders from beryllium metal production were of high purity with only a minor component of beryllium oxide. Both particles and powders from oxide production were high-purity oxide. Particles released during production of copper-beryllium alloy were heterogeneous, being predominantly copper oxides. Thus, all particles and powders contain at least some beryllium in the form of beryllium oxide. These data justify efforts to thoroughly characterize beryllium aerosol properties when performing exposure assessments. The data also suggest that differences in particle chemical composition, size, number, and surface area may influence bioavailability of beryllium and contribute to risk of CBD. However, a scientific basis does not yet exist to replace mass as the current metric of exposure.
Tension pneumomediastinum is a rare complication of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection that has increased in incidence with the novel coronavirus disease 2019 ...pandemic. Although traditionally managed with conservative measures, we present the indications and methods for the first operative management of tension pneumomediastinum with concomitant SARS-CoV-2 infection.
15N NMR measurements on the title compound (1,8-bis(dimethylamino)naphthalene, DMAN) and its protonated derivative, show the presence of an unsymmetrical NHN
+ structure in the protonated form. ...This conclusion is reached from a consideration both of the nitrogen shieldings and of the
1J(
15N
1H) results observed.
Control of workplace exposure to beryllium is a growing issue in the United States and other nations. As the health risks associated with low-level exposure to beryllium are better understood, the ...need increases for improved analytical techniques both in the laboratory and in the field. These techniques also require a greater degree of standardization to permit reliable comparison of data obtained from different locations and at different times. Analysis of low-level beryllium samples, in the form of air filters or surface wipes, is frequently required for workplace monitoring or to provide data to support decision-making on implementation of exposure controls. In the United States and the United Kingdom, the current permissible exposure level is 2 microg m(-3) (air) and the United States Department of Energy has implemented an action level of 0.2 microg m(-3) (air) and 0.2 microg/100 cm(2) (surface). These low-level samples present a number of analytical challenges, including (1) a lack of suitable standard reference materials, (2) unknown robustness of sample preparation techniques, (3) interferences during analysis, (4) sensitivity (sufficiently low detection limits), (5) specificity (beryllium speciation) and (6) data comparability among laboratories. Additionally, there is a need for portable, real-time (or near real-time) equipment for beryllium air monitoring and surface wipe analysis that is both laboratory-validated and field-validated in a manner that would be accepted by national and/or international standards organizations. This paper provides a review of the current analytical requirements for trace-level beryllium analysis for worker protection and also addresses issues that may change those requirements. The current analytical state of the art and relevant challenges facing the analytical community will be presented, followed by suggested criteria for real-time monitoring equipment. Recognizing and addressing these challenges will present opportunities for laboratories, research and development organizations, instrument manufacturers and others.
13C and
15N CP-MAS NMR measurements are reported for four mesoionic type A oxa- and thiatriazoles. X-ray structures are also reported for compounds
1 and
2. The results obtained show close similarity ...between the solid and solution structures for these molecules. The phenyl and mesoionic rings are nearly coplanar and the bond orders of the C5-Y
− bonds are close to 1.5. The relative cis and trans positions of the components of the exocyclic groups, with respect to the mesoionic ring sulphur atom, are also reported.
15
N NMR chemical shift values (but not the
1
J
NP
values) are a good indication of the relative basicities of nitrogens in phosphoramidates, as demonstrated by the rates of the acid-catalysed ...cleavage of the exo- and endocyclic P-N bond in selected substrates.
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