Linear Trimeric Hafnium Clusters in Hf 0
The reduction of hafnium tetraiodide, HfI4, with aluminum at 600 °C or 850 °C in the presence of a NaI flux resulted in black single crystals of Hf0.86(1)I3. This composition corresponds well to the upper end of the non-stoichiometry range 0.89 ≤ x ≤ 1.00 previously reported for HfxI3. The crystal structure (a = 1250.3(2), c = 1999.6(3) pm, R-3m, Z = 18) is made up of hexagonal closest packed layers of iodide ions. One third of the octahedral holes would be filled as in TiI3 or ZrI3 if it were Hf1.00I3. In Hf0.86(1)I3, one out of six octahedral holes along [001] are, however, only occupied by 16%. In contrast to TiI3-I and ZrI3, one striking structural feature is in the formation of linear hafnium trimers with identical Hf―Hf distances of 318.3(2) pm rather than the formation of dimers. These may be associated with Hf―Hf bonding although only 2.64 electrons are available for one Hf5.16I18 column.
Kristallstruktur von Zirkoniumtetrajodid ZrI4: ein neuer AB4‐strukturtyp
The crystal structure of ZrI 4 was determined from Xray diffractometer data and was refined by full-matrix least-squares methods to an R index of 0-045 for 1985 observed reflexions. The crystals are monoclinic, space group P2/c with a = 8.356 (2), b = 8.326 (2), c = 17.926 (4) A, fl = 103.21 (3) ° , V = 1214. I A 3, D x = 4.914 Mg m -3, Z = 6 ZrI 4. The structure consists of infinite chains of ZrI 6 octahedra sharing non-opposite edges in such a way that a helical arrangement with an identity period of six octahedra along the chain results. It appears to be the first AB 4 structure of its type, different from the ct-NbI 4, ZrCI4, and fl-ReCl 4 chain structures. Z r I distances range from 2 . 6 9 2 ( 1 ) t o 3.030 (1) A, Z r Z r separations along the chains are 0567-7408/79/020274-05501.00 uniform [4.394 (1) and 4.416 (1) AI; I I distances within the c.c.p, anion arrangement are 3 .8994.199 (1) A within the chains and 4.103-4.413 (1) A between the chains.
As práticas profissionais no campo público de atenção à saúde bucal: o caso de dois municípios da Bahia
This paper examines the working facilities and processes of dentists in the primary healthcare systems of two towns in Bahia State, Brazil, striving to analyze the extent to which factors related to dental care, training, placement and professional profiles influence their practices. Semi-structured interviews were conducted with nine dentists in both towns, with work process organization patterns in Municipality C being closer to the structuring principles of Brazil's National Health System than in Municipality E. This seems to be related to management characteristics, with networking links among individual, collective, and preventive clinical activities and planning noted in Municipality C. Despite these differences, the practitioners presented similarities in terms of dual militancy and perceptions of the public and private healthcare fields. The hegemony of the private sector seems to be influencing the professional practices of dentists in the public health system.