Electrochemical and spectroscopic investigation of the reduction of dimethylglyoxime at mercury electrodes in the presence of cobalt and nickel

Voltammograms (polarograms) obtained from solutions of cobalt and nickel containing dimethylglyoxime (dmgH(2)) are widely used for the trace determination of these metals. Detailed electrochemical and spectroscopic studies on the reduction process observed in the analytically important ammonia buffer media at mercury dropping, hanging, and pool electrodes are all consistent with an overall 10-electron reduction process, in which both the dmgH(2) ligand and cobalt ions are reduced in the adsorbed state:  Co(II) + 2dmgH(2) ⇌ (solution) [Co(II)(dmgH)(2)] + 2H(+); [Co(II)(dmgH)(2)] + Hg ⇌ (electrode) [Co(II)(dmgH)(2)](ads)Hg; and [Co(II)(dmgH)(2)](ads)Hg + 10e(-) + 10H(+) → Co(Hg) + 2[2,3-bis(hydroxylamino)butane]. The limited solubility of the nickel complex in aqueous media restricts the range of studies that can be undertaken with this system, but an analogous mechanism is believed to occur. Low-temperature voltammetric studies in dichloromethane at a frozen hanging mercury drop electrode and in situ electron spin resonance electrochemical measurements on more soluble analogues of the dimethylglyoxime complexes are consistent with an initial one-electron reduction step being available in the absence of water. Deliberate addition of water to acetone solutions enables the influence of the aqueous environment on voltammograms and polarograms to be examined. The results of the present study are compared with the wide range of mechanisms proposed in other studies.

Do indoor pollutants and thermal conditions in schools influence student performance? A critical review of the literature

To assess whether school environments can adversely affect academic performance, we review scientific evidence relating indoor pollutants and thermal conditions, in schools or other indoor environments, to human performance or attendance. We critically review evidence for direct associations between these aspects of indoor environmental quality (IEQ) and performance or attendance. Secondarily, we summarize, without critique, evidence on indirect connections potentially linking IEQ to performance or attendance. Regarding direct associations, little strongly designed research was available. Persuasive evidence links higher indoor concentrations of NO(2) to reduced school attendance, and suggestive evidence links low ventilation rates to reduced performance. Regarding indirect associations, many studies link indoor dampness and microbiologic pollutants (primarily in homes) to asthma exacerbations and respiratory infections, which in turn have been related to reduced performance and attendance. Also, much evidence links poor IEQ (e.g. low ventilation rate, excess moisture, or formaldehyde) with adverse health effects in children and adults and documents dampness problems and inadequate ventilation as common in schools. Overall, evidence suggests that poor IEQ in schools is common and adversely influences the performance and attendance of students, primarily through health effects from indoor pollutants. Evidence is available to justify (i) immediate actions to assess and improve IEQ in schools and (ii) focused research to guide IEQ improvements in schools.

PRACTICAL IMPLICATIONS

There is more justification now for improving IEQ in schools to reduce health risks to students than to reduce performance or attendance risks. However, as IEQ-performance links are likely to operate largely through effects of IEQ on health, IEQ improvements that benefit the health of students are likely to have performance and attendance benefits as well. Immediate actions are warranted in schools to prevent dampness problems, inadequate ventilation, and excess indoor exposures to substances such as NO(2) and formaldehyde. Also, siting of new schools in areas with lower outdoor pollutant levels is preferable.

The physical and chemical nature of technegas

Technegas, the discrete radio-aerosol particle, containing 99mTc has been investigated, and the chemical evolution and physical properties of the particle demonstrated.

METHODS

A commercial technegas generator was used to produce aerosols according to standard clinical procedures. The aerosols were collected by electrostatic precipitation and examined with transition electron microscopy (TEM), scanning electron microscopy (SEM) and force microscopy. The chemical evolution was examined by x-ray techniques and thermogravimetric analysis.

RESULTS

The active particle was identified as hexagonal platelets of metallic technetium contained within a thin layer of graphitic carbon. This composite structure is discussed in light of the metal particle behaving as a template for the carbon capsule. The average size of the observed hexagonal platelets, 30-60 nm, was only weakly dependent on the concentration of technetium in the crucible.

CONCLUSION

The mechanism for the formation of the technegas pancreas has been developed and the particles involved characterized. It appears that the use of other metals also leads to the formation of similar materials.

Alternatives to psychiatric hospitalization for children

The impetus for the dramatic increase in the number of treatment alternatives for children has come from changes in the theoretical conceptualization of treatment, social and political pressures, and financial considerations. This article reviews the literature on alternatives to hospitalization, appraising the available data on the effectiveness of psychiatric hospitalization and its alternatives and considers future research needs and the development of services in this area.

Diagnosis and childhood firesetting

This paper presents findings on the relationship of childhood firesetting and DSM-III diagnosis in a representative sample of child psychiatric outpatients (N = 204). Childhood firesetting and the DSM-III diagnosis of conduct disorder are strongly related; they show a significant interaction effect with lessened competence as measured by activities and increased externalizing (undercontrolled) behavior.

Association of fragile X syndrome with autism

The fragile X syndrome has been associated with autism. Blood samples from 37 autistic children and a control group were negative for fragile X chromosome. Large numbers of nonrandom autosomal lesions were observed in both the autistic and control groups.

Tris(dithioacetylacetonato)chromium(III)

The synthesis of the first dithioaoetylacetonate of a Group VI transition metal has been achieved by reduction of the 3,5-dimethyl-1,2-dithiolium cation with divalent chromium. The physical properties of the dark green monomer [Cr(SacSac)3] are reported.

The synthesis and properties of Tris(dithioacetylacetonato) complexes of cobalt(III), rhodium(III), and iridium(III)

.The syntheses of the cobalt(III), rhodium(III), and iridium(III) complexes of dithioacetylacetone, [M(SacSac)3], are described. The tris-chelates are neutral dia- magnetic monomers. Infrared, proton magnetic resonance, and electronic spectra are reported. Polarography in acetone shows that these complexes are reduced at more negative potentials than those of the iron(III) group. Various related complexes [Co(SacSac)2(X-Y)] have also been prepared.

The synthesis and properties of tris(dithioacetylacetonato) complexes of iron(III), ruthenium(III), and osmium(III)

The syntheses of the iron(111), ruthenium(111), and osmium(111) complexes of dithioacetylacetone are described. The tris chelates are neutral low-spin (S = 1/2)monomers. Polarography in acetone reveals a ready one-electron reduction for each complex. Infrared and e.s.r. spectra are reported. The magnetic susceptibilities have been measured as a function of temperature. The electronic absorption spectra are compared with those of the related cobalt(111) group complexes, and some tentative assignments of charge transfer bands are provided.

A ruthenium chloro nitrosyl derivative of dithioacetylacetone

The novel dithioacetylacetonato complex [Ru(C5H7S2)2(NO)Cl] has been characterized by analytical and spectral methods. A trans configuration is suggested. The electronic spectrum is consistent with the oxidation state II for the coordinated metal ion.