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Notes: The mode transition from a capacitively coupled mode (E mode) to an inductively coupled mode (H mode) was observed in an inductive Ar plasma source by applying an axially uniform low B field. The applied fundamental rf was 13.56 MHz and many harmonic components were observed. A beat and standing wave patterns of azimuthally symmetric (m=0 mode) first and second harmonic pseudosurfaces and helicon waves were measured at various densities (n∼9.0×1010–2.2×1011 cm−3) and B fields (12–28 G). Wave propagation mode changes, from pseudosurface to helicon waves and from helicon to pseudosurface waves, were observed at critical conditions, ωc/ω〉3.0 and n∼2.2×1011 cm−3. © 1998 American Institute of Physics.

Notes: Micromotion of ions in Paul traps has several adverse effects, including alterations of atomic transition line shapes, significant second-order Doppler shifts in high-accuracy studies, and limited confinement time in the absence of cooling. The ac electric field that causes the micromotion may also induce significant Stark shifts in atomic transitions. We describe three methods of detecting micromotion. The first relies on the change of the average ion position as the trap potentials are changed. The second monitors the amplitude of the sidebands of a narrow atomic transition, caused by the first-order Doppler shift due to the micromotion. The last technique detects the Doppler shift induced modulation of the fluorescence rate of a broad atomic transition. We discuss the detection sensitivity of each method to Doppler and Stark shifts, and show experimental results using the last technique.

Notes: Dissolved paramagnetic ions generally provide an efficient mechanism for the relaxation of nuclear spins in solution, a phenomenon called the nuclear magnetic resonance-paramagnetic relaxation enhancement (NMR-PRE). Metal ions with electron spins S≥1 exhibit rich NMR relaxation phenomena originating in the properties of the zero-field splitting (zfs) interaction, which vanishes for spin-〈fraction SHAPE="CASE"〉12 ions but which is nonzero for S≥1 ions in site symmetry lower than cubic. For S≥1 ions in the vicinity of the zfs-limit, i.e., at magnetic-field strengths low enough that the zfs energy exceeds the Zeeman energy, the NMR-PRE depends strongly on the detailed structure of the electron spin energy levels as well as on the spatial quantization of the spin motion. It is shown theoretically and experimentally that the NMR-PRE produced by integer spins can be influenced strongly by the small intradoublet zero-field splittings, i.e., the splittings between the components of the non-Kramers doublets, which are produced by noncylindrical components of the crystal field potential. These small splittings produce relatively low-frequency oscillations in the dipolar field associated with 〈Sz(circumflex)〉 (the spin component along the molecule-fixed z(circumflex) axis). These motions decouple the nuclear spin from the electron spin, thereby depressing, in some cases very strongly, the NMR-PRE. The presence of a relatively small Zeeman field, comparable in magnitude to the intradoublet spacing but small compared to the larger interdoublet zfs splittings, causes a major change in the spin wave functions which has profound effects on the motions of the electron spin. When the Zeeman energy exceeds the small zfs splitting, the oscillatory motion of 〈Sz(circumflex)〉 damps out, with the result that the electron spin couples more effectively to the nuclear spin, providing a more efficient NMR relaxation pathway. NMR-PRE data are presented for the S=1 complex Ni(II)(o-pda)2Cl2 (o-pda=ortho-phenylenediamine) which confirm the importance of the splitting of the mS=±1 non-Kramers doublet on the NMR relaxation efficiency. The zfs E-parameter was measured from the NMR data to be |E|=0.26 cm−1. The S=2 spin system, Mn(III)-tetraphenylporphyrin sulfonate, exhibits a related phenomenon which arises from the effects of a small zfs splitting, Δε±2, of the mS=±2 non-Kramers doublet that is caused by a fourfold rotational component of the crystal field potential. The splitting Δε±2 was measured from NMR data to be 0.20 cm−1. © 1998 American Institute of Physics.

Notes: Summary: There is now convincing evidence that CD8+ T cells can be activated by professional antigen-presenting ceils which present antigens derived from non-lymphoid tissues in association with MHC class I molecules in the draining lymph nodes. This mechanism, referred to as cross-presentation, enables the immune system to respond to those microorganisms that infect only non-lymphoid tissues. Consistent with this view, cross-presentation was found to focus on antigens expressed in high concentrations and those released from dying cells, which can be expected to result from viral infections. Recent evidence, however, demonstrates that high dose self antigens can be cross-presented constitutively, resulting m the activation of autoreactive CD8+ T cells. This does not lead to auto-immunity under physiologic conditions, but to CD95-mediated deletion of the T cells. Cross-presentation can thus engage a well-defined pathway of antigen-induced T-cell death and purge the immune system of autoreactive CD8+ T cells. Low dose self antigens are not cross-presented and are consequently ignored. The immune system therefore uses two strategies to avoid CD8+ T-cell-mediated autoimmunity in the periphery: deletion of autoreactive CD8+ T cells responding to high dose self antigens and ignorance of self antigens expressed at low concentrations.

Notes: Growth of Atlantic walruses (Odobenus rosmarus rosmarus) was investigated using morphological data collected in association with Inuit subsistence walrus hunts. Four growth models were examined. The growth parameters of a constrained Richards model were used to quantify growth and to test for sexual dimorphism. The asymptotic length of male walruses (315.2 cm ± 3.8 (SE), n= 103) was significantly larger (t= 7.21, df = 191, P 〈 0.05) than the asymptotic length of females (276.6 cm ± 3.4, n= 90). Sexual size dimorphism in adults was due to a longer growth period and a faster growth rate in males. The predictive equation relating mass (M, kg) to standard length (SL, cm) was: Log10M= -3.74 + 2.68(Log10SL), n= 25, r2= 0.98. There were no significant differences in the size of male walruses from Foxe Basin collected in the 1950s and this study. There were too few data to compare females. There were no significant differences in size between walruses sampled in Greenland and Foxe Basin in the 1980s and 1990s. Foxe Basin walruses were significantly larger than walruses sampled in northern Hudson Bay in the 1950s. Female Atlantic walruses sampled in Foxe Basin were larger than female Pacific walruses (Odobenus rosmarus divergens) sampled in Alaska.

Notes: Although numerous studies recently have appeared that identify the most-cited scholars and works in the general criminology and criminal justice literature and in several specialty areas, no previous citation study has specifically examined the police studies literature. Through an analysis of 370 articles and research notes appearing from 1991 to 1995 in the areas of police studies, published in Criminology, Justice Quarterly, and four academic periodicals devoted to police studies, we list the 50 most-cited scholars and the 36 most-cited works. The lists of the most-cited scholars and works in the specialty area of police studies are compared to general lists taken from leading criminology and criminal justice journals and introductory textbooks. We conclude with some thoughts about the relevance of citation analysis to specialists in police studies.

Notes: The α-toxin of Clostridium perfringens is the major virulence determinant for gas gangrene in man. The gene encoding the α-toxin has been cloned into E. coli from two strains of the bacterium (NCTC8237 and CER89L43) and subsequently purified to homogeneity. The two strains of α-toxin differ by five amino acids, resulting in the toxin from NCTC8237 being sensitive to chymotrypsin digestion while that from CER89L43 is resistant. The α-toxin from each of these strains has been crystallized in two different forms by the hanging-drop vapour-diffusion method at 293 K. CER89L43 form I crystals belong to space group R32 and have two molecules in the crystallographic asymmetric unit and a unit cell with a = b = 151.4, c = 195.5 Å, α = β = 90, γ = 120°. The crystals diffracted to dmin = 1.90 Å. The characteristics of the NCTC8237 form I crystals have already been reported. The form II crystals from both strains belong to space group C2221 with one molecule in the crystallographic asymmetric unit and, for strain CER89L43, have cell dimensions a = 61.05, b = 177.50, c = 79.05 Å, α = β = γ = 90°, while for strain NCTC8237 the cell dimensions are a = 60.50, b = 175.70, c = 80.20 Å, α = β = γ = 90°. The crystals diffracted to maximum resolutions of 1.85 and 2.1 Å for the CER89L43 and the NCTC8237 strains, respectively.