Structural, electronic, and chemical properties of multiply iodized aluminum clusters.

The electronic structure, stability, and reactivity of iodized aluminum clusters, which have been investigated via reactivity studies, are examined by first-principles gradient corrected density functional calculations. The observed behavior of Al13I(x)- and Al14I(x)- clusters is shown to indicate that for x < or = 8, they consist of compact Al13- and Al14++ cores, respectively, demonstrating that they behave as halogen- or alkaline earth-like superatoms. For x > 8, the Al cores assume a cagelike structure associated with the charging of the cores. The observed mass spectra of the reacted clusters reveal that Al13I(x)- species are more stable for even x while Al14I(x)- exhibit enhanced stability for odd x(x > or = 3). It is shown that these observations are linked to the formation and filling of "active sites," demonstrating a novel chemistry of superatoms.

Al cluster superatoms as halogens in polyhalides and as alkaline earths in iodide salts.

Two classes of gas-phase aluminum-iodine clusters have been identified whose stability and reactivity can be understood in terms of the spherical shell jellium model. Experimental reactivity studies show that the Al13I-x clusters exhibit pronounced stability for even numbers of I atoms. Theoretical investigations reveal that the enhanced stability is associated with complementary pairs of I atoms occupying the on-top sites on the opposing Al atoms of the Al13- core. We also report the existence of another series, Al14I-x, that exhibits stability for odd numbers of I atoms. This series can be described as consisting of an Al14I-3 core upon which the I atoms occupy on-top locations around the Al atoms. The potential synthetic utility of superatom chemistry built upon these motifs is addressed.

The nature and incidence of complications of peripheral arterial puncture.

Follow-up of the sites of 839 peripheral arterial punctures has confirmed the technique as safe and free from major sequelae. Minor complications, mainly bruising and tenderness, occurred at 39% of sites; this incidence is much less than that previously reported following short-term arterial cannulation. At only 2% of sites was there any significant pain or tenderness. There was a small incidence of pulse diminution particularly at the radial site but no case of arterial occlusion. The use of a smaller needle (23 s.w.g.) significantly reduced the overall incidence of complications.

Coloured pattern displacement and VEP amplitude.

The results of this experiment confirm that evoked potential amplitude is linear with checkerboard pattern displacement. We have also found that this linear relationship holds for red, green and blue patterns. The hypothesis that there would be no significant differences between the amplitude of the evoked potential to colour/'black' stimulation and a white/'black' stimulus of equivalent luminance has been substituted. Differences were found between colours. The mean level for the blue pattern was lower than that for the red and the green patterns. We have further confirmed the relationship between luminance and the latency of the evoked potential. Differences in latency were found between all conditions in this study, suggesting that more accurate methods of measuring luminance are required in studies using colour pattern displacement if latency measurements are the main focus of the study.

Location of Grapevine Fardeaf and Yellow Mosaic Virus Particles in Xiphinema index.

Particles of fanleaf and yellow mosaic viruses are reported in the lumen of the esophagus of Xiphinerna index. Differences in cuticular morphology suggest differences in charged receptor sites which may offer an explanation for virus location and orderly arrangement.

Cilia in nematode sensory organs.

Electron microscopic studies revealed thle presenlce of true cilia in nerve processes connected with sensory organs of a nemnatodes. These structures are important in evaluating the relation between nematodes and the other aschelminths, from which they were separated partially on the basis of the supposed total absence of cilia.