Density functional theory based screening of ternary alkali-transition metal borohydrides: a computational material design project.

We present a computational screening study of ternary metal borohydrides for reversible hydrogen storage based on density functional theory. We investigate the stability and decomposition of alloys containing 1 alkali metal atom, Li, Na, or K (M(1)); and 1 alkali, alkaline earth or 3d/4d transition metal atom (M(2)) plus two to five (BH(4))(-) groups, i.e., M(1)M(2)(BH(4))(2-5), using a number of model structures with trigonal, tetrahedral, octahedral, and free coordination of the metal borohydride complexes. Of the over 700 investigated structures, about 20 were predicted to form potentially stable alloys with promising decomposition energies. The M(1)(Al/Mn/Fe)(BH(4))(4), (Li/Na)Zn(BH(4))(3), and (Na/K)(Ni/Co)(BH(4))(3) alloys are found to be the most promising, followed by selected M(1)(Nb/Rh)(BH(4))(4) alloys.

[Low back pain syndrome in coal miners: preliminary results of an epidemiological study]. / Bóle krzyza u górników kopaln wegla kamiennego--wstepne wyniki badan.

The objective of the study was to determine the occurrence of low-back-pain syndrome in coal-miners and to compare the results obtained in the study and control groups. In two groups of subjects (624 employees of the 'Staszic' and 598 employees of the 'Sosnica' mines) the survey and medical assessment were performed and available medical records reviewed. Two groups were similar in terms of age and employment duration, however, working conditions in the 'Sosnica' mine were more difficult, and associated with a larger physical burden. All workers were divided into three groups according to the workload: workers with 'heavy workload' (35.9%), 'medium workload' (37.6%), and 'light workload'. The control group consisted of 449 policemen matched by age and the number of years preceding their retirement. The study revealed that low-back-pain syndrome occurred in 66.4% and 62.2% of the 'Sosnica' and 'Staszic' miners, respectively, while in policemen this figure accounted for only 7.5%. Among miners and policemen, a group with the employment ranging from 10 to 20 years was identified. The group comprised 730 miners, including 179 persons with light workload, and 142 policemen. Law-back-pain occurred in 61.6% of miners and in 14.1% of policemen. In miners the syndrome was associated mainly with lifting heavy objects or with an inappropriate forced position of the body at work. The preliminary results of the epidemiological study indicated that low-back-pain syndrome occurred more frequently in coal-miners than in policemen.