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ABSTRACTNontyphoidal salmonellae, particularly Salmonella entericaserovar Typhimurium, are a major cause of invasive disease in Africa, affecting mainly young children and HIV-infected individuals. Glycoconjugate vaccines provide a safe and reliable strategy against invasive polysaccharide-encapsulated pathogens, and lipopolysaccharide (LPS) is a target of protective immune responses. With the aim of designing an effective vaccine against S. Typhimurium, we have synthesized different glycoconjugates, by linking O-antigen and core sugars (OAg) of LPS to the nontoxic mutant of diphtheria toxin (CRM197). The OAg-CRM197conjugates varied in (i) OAg source, with three S. Typhimurium strains used for OAg extraction, producing OAg with differences in structural specificities, (ii) OAg chain length, and (iii) OAg/CRM197ratio. All glycoconjugates were compared for immunogenicity and ability to induce serum bactericidal activity in mice. In vivoenhancement of bacterial clearance was assessed for a selected S. Typhimurium glycoconjugate by challenge with live Salmonella. We found that the largest anti-OAg antibody responses were elicited by (i) vaccines synthesized from OAg with the highest glucosylation levels, (ii) OAg composed of mixed- or medium-molecular-weight populations, and (iii) a lower OAg/CRM197ratio. In addition, we found that bactericidal activity can be influenced by S. Typhimurium OAg strain, most likely as a result of differences in OAg O-acetylation and glucosylation. Finally, we confirmed that mice immunized with the selected OAg-conjugate were protected against S. Typhimurium colonization of the spleen and liver. In conclusion, our findings indicate that differences in the design of OAg-based glycoconjugate vaccines against invasive African S. Typhimurium can have profound effects on immunogenicity and therefore optimal vaccine design requires careful consideration.

Analysis of conjugate data from extended magnetometer networks in northern and southern high latitudes is used to elucidate the initiation and the evolution of a magnetic impulse event (MIE) on June 6, 1997. In addition, data from all‐sky imagers, imaging riometers, and Super Dual Auroral Radar Network radars in Antarctica are investigated to confirm the energy content, motion, and electrical current structure of the MIE. The MIE was accompanied by traveling convection vortices (TCVs) that began at ∼10 MLT and moved eastward (toward dusk) and slightly equatorward at 1–3 km/s across the noon meridian with north‐south conjugacy. The MIE had upward field‐aligned currents with soft electron precipitation that was located near the trailing edge of the Hall current loop. During the MIE interval the interplanetary magnetic field (IMF) was directed strongly outward from the Sun (Bx= −5 nT), with a slightly positive (1–2 nT) Bz, and a nearly zero By. Since abrupt solar wind pressure changes are unlikely under this IMF orientation (and none was, in fact, observed), classical mechanisms for MIE generation, such as a pressure pulse or dayside reconnection, are excluded. It is speculated that an abrupt IMF cone angle change from 60° to 20°, ∼30 min prior to the MIE onset, may have been an indirect trigger of this event via the interaction between the solar wind and the bow shock.

Sudden, short‐lived dayside auroral activity is often observed equatorward of the quiescent auroral oval. Several cases from the 1996 South Pole and United States Automatic Geophysical Observatory data were examined. In all cases the optical events were accompanied by well‐correlated magnetic impulsive events. Most optical auroral activity was primarily in 630‐nm emission (soft electron precipitation presumably of plasma sheet or magnetosheath origin). Most optical events also show the presence of much shorter lived 427.8‐nm emission (harder electron precipitation with associated electron acceleration). In almost all events the keograms showed repeated poleward propagation, indicating that the event started at lower latitudes and propagated to higher latitudes. The optical emissions showed distinct periodicities, which usually correlated well with the magnetic signature. All the events began equatorward of the preexisting quiescent aurora, indicating that they initiated in the region of closed field lines. The interplanetary magnetic field Bzcomponent prior to the events was either small or positive in most cases. The majority of the observed events were consistent with being triggered by interplanetary Bzor solar wind pressure change. For some events, no specific trigger was found.

We have developed and examined a new regional geomagnetic index AES-80, defined similarly to the classical auroral electrojet AE index, using data from five Antarctic stations located at corrected geomagnetic latitudes about 80 °S. Because only sparse ground-based information can be derived from auroral latitudes in the Southern Hemisphere, and because no index comparable to AE can be constructed from locations in the south, the possibility of using AES-80 as a measure of high latitudes and polar cap activity is investigated. As a global average activity level indicator, it is found that in general AES-80 gives results rather similar to the classical AE index. However AES-80 provides a more robust measure of the occurrence of high-latitude geomagnetic activity.

A new index AES-80 was derived in order to provide a measure of the geomagnetic activity at high southern latitudes (Ballatore et al., 1998). The comparison between the southern hemisphere AES-80 with the northern hemisphere PC index is reported here for the period May 1994–April 1995. It is found that during southward IMF the two parameters record the geomagnetic disturbances rather similarly. In contrast, during northward IMF, only AES-80 is capable of recording geomagnetic activity occurring in the nominal polar cap region. In agreement with this finding, a slightly higher correlation coefficient is found between AES-80 and PC during southward IMF than during the northward IMF condition. Although at any time the two indices reflect opposite seasons, the overall correlations found between the two indices are significant, independent of the specific UT interval considered. The UT modulation (which should possibly be taken into account in the use of the indices) has been calculated for the AES-80 and the PC index. The results show that, for the specific period considered, the PC index dependence on UT is more significant than that of the AES-80 parameter.

In myasthenia gravis (MG), extraocular muscle (EOM) weakness is often an initial and persisting symptom. It has been proposed that acetylcholine receptor (AChR) from EOM is antigenically different from AChR of other innervated muscles and that the presence of antibodies to fetal AChR expressed in EOM causes their weakness. We have (1) studied mRNA expression for each of the AChR subunits (α, β, γ, δ, and ϵ) in human muscle, including EOM, and (2) compared the binding of sera from ocular myasthenia gravis (OMG) patients with fetal (α2βγδ) and adult (α2βϵδ) human AChRs. RNase protection assays showed that expression of the AChR γ‐subunit (fetal‐type) mRNA in EOM was comparable with that in other innervated muscle types. By contrast, ϵ‐subunit (adult‐type) mRNA was expressed at much higher levels in EOM than in other muscles studied. Moreover, some OMG sera bound specifically to adult AChR. These results do not support the contention that susceptibility of EOM in MG results from expression of fetal AChR and indicate that the inclusion of antigen from a source rich in adult AChR in the MG diagnostic assay will increase the yield of positive results in OMG patients.

Throughout 1993, as the Ulysses spacecraft traveled from ~23° to ~45° south heliolatitude, the HI-SCALE instrument on the spacecraft measured a recurrent series of enhanced particle fluxes with a recurrence period of ~26.5 days. These particles are accelerated from a background seed population by the corotating interaction regions (CIRs) associated with a southern solar polar coronal hole. Using the Wart detector telescope of the HI-SCALE instrument, we have analyzed the elemental abundances of C, N, O, and Fe relative to He for 0.5–4.0 MeV/nucl ions and Ne, Mg, and Si for 1.0–4.0 MeV/nucl ions in the CIRs. We compare the relative abundances to some previous measurements reported from 1 A.U. as well as with solar photosphere abundances. We note that HI-SCALE measurements of the heliolatitude dependence of the oxygen abundance and spectrum as reported by Lanzerottiet al. (1994) suggest that a substantial fraction of the seed population for the CIR-accelerated oxygen is likely to be the anomalous oxygen component of the cosmic rays.

We report the results of a study of the 12-hour average distribution functions of high Z nuclei as measured over a 10-day interval on the Ulysses spacecraft at a helioradius of~5.2 A.U. We use the good time and atomic mass resolution of the composition aperture of the HI-SCALE instrument to determine the form of the distribution functions for C, O, Ne, Mg, Si, and Fe over the energy range ~0.5–16 MeV/nucl. We find that the distribution functions of these ions can be organized by characteristic velocities that have values ranging between~2000–3500 km/sec over this interval.

Magnetic fluctuations in the hydromagnetic frequency band ~0 to ~0.05 Hz are examined at magnetospheric cusp latitudes during two times when ionospheric signatures of possible flux-transfer events were evident in the data. Ultralow frequency power is found to be very broad band in the range ~0.02–0.05 Hz and to be more narrowly confined at a frequency ~0.0025 Hz. At lower latitudes, the higher frequency (broad-band) power excites narrower-band field line resonances at the fundamental frequency of the respective field line — a standing Alfvén wave. The narrow-band power in the lower frequency band (period around 400 s) is approximately that expected for a field line resonance on a closed field line near the magnetopause; it also corresponds approximately to the width of the convected field-aligned current filament as observed on the ground. The reconnection process at the dayside magnetopause evidently plays an important role in the generation of low-frequency (?0.008 Hz) hydromagnetic energy in the dayside magnetosphere, energy which can produce Alfvén waves deeper in the magnetosphere.

Simultaneous measurements of magnetic field variations at the nominally conjugate sites of South Pole station, Antarctica, and Iqaluit, Canada, have been used to study latitude differences in the location of corresponding westward electrojets in the nightside polar cap. Substorm-related auroral events were selected from 1986 data with the criterion that the magnitude of the negative bay exceed 100 nT in at least one hemisphere and that the electrojet, oriented mainly in the magnetic east–west direction, pass overhead of this station. The resulting data base comprised 60 events distributed seasonally as follows: austral summer (17); fall (6); winter (18); spring (19). The interhemispheric latitude difference in the locations of the electrojets was obtained by examining the ratio of the vertical and horizontal component magnetic variations. Seasonal and diurnal variations of the latitude of westward electrojets were evident during solstice periods. In particular, it is noted that the substorm westward electrojet flows at higher latitudes in the winter hemisphere than in the summer hemisphere, after 2000 MLT. The latitude difference between the two hemispheres maximizes at ~4° near local midnight. The latitude difference becomes smaller away from midnight and reverses for local times prior to ~2000 MLT. The observed seasonal and diurnal variations are generally consistent with predictions of the effect of the magnetic dipole tilt on the location of last closed field lines. However, because on the nightside the field lines originating from South Pole station and Iqaluit reach deep into the magnetotail, they are likely to be influenced by the plasma sheet. Thus the implications of an asymmetric distribution of the plasma sheet with respect to the neutral sheet have also been considered. Such a postulated distribution can account for the seasonal variations while conserving magnetic flux and maintaining pressure balance across the tail.

The movement of the seawater across the earth's magnetic field produces a large-scale motional electric field. Using the Point Arena, California, to Hanauma Bay, Hawaii, unpowered HAW-1 cable, we have studied the geopotential across this distance to look for possible tsunami-induced fields that might have been produced following the April 1992 Cape Mendocino earthquake. We have used a ten-day interval prior to and including the earthquake as a reference for geopotential signals and for geomagnetic activity. We have also used geomagnetic data from Point Arena, Honolulu and Boulder as reference data. The results of the analyses show that there are tsunami-related effects in the cable geopotential data. These are (a) larger voltage prediction errors (residuals) for the interval following the main shock; (b) enhanced (compared to the 10d reference interval) geopotential spectral power following the main shock: two enhancements are larger than geomagnetically-induced spectral power enhancements in the same time interval; and (c) strong evidence for an ~30 min “echo” in the cable geopotential signal following the main shock.

Voyager 2 low‐energy charged particle (LECP) data from the magnetosphere of Uranus have been analyzed to obtain proton and electron phase space density profiles. The Uranus proton profiles show an approximately exponential decline with decreasing radius for L≲ 9 in a relatively dense thermal plasma region with intense plasma wave activity. An analogy with the magnetospheres of Earth, Jupiter, and Saturn suggests a plasmasphere at Uranus. The ion flux tube content in the Uranian radiation belt is less than that in the other three cases. Proton and electron profiles ≲ 100 MeV/G show evidence of an absorption signature near the minimum Lof Ariel. Proton profiles ≳ 200 MeV/G show evidence of injection events, suggesting substorm processes at Uranus. Electron profiles ≳ 100 MeV/G show clear minima at the minimum Lvalues of Miranda, Ariel, and perhaps Umbriel, separated by broad maxima. These profiles are interpreted as implying local injection of energetic electrons. Distributed loss mechanisms at Uranus include satellite sweeping, wave‐particle interactions, and charge exchange of protons with an extended hydrogen corona. If the net loss rates of protons and electrons are estimated by calculated satellite sweeping rates, the radial diffusion coefficient is estimated near L= 7.5 to be 10−7s−1to 10−6s−1. If the diffusion coefficient is ≲ 10−6s−1, the power available from inward radial diffusion of energetic protons and electrons is ≲ 5 × 108W and is less than the 4 × 1010W needed to maintain the Uranian ultraviolet aurora. Local injection of electrons above 100 MeV/G between the minimum Lvalues of Miranda and Ariel also requires a power of at least 8 × 107. The magnetosphere of Uranus is the third planetary magnetosphere for which evidence of substorm activity has been adduced, after those of Earth and Mercury.

Measurements of the ion and electron fluxes in the Uranian magnetosphere made by the low‐energy charged particle (LECP) instrument on the Voyager 2 spacecraft are used to discuss possible particle‐induced modifications of the moons and rings of Uranus. The energy spectra of the orbit‐integrated particle dosages expected on the major moons are derived from the LECP measurements of particle intensities and pitch angle distributions. Laboratory‐derived results on charged‐particle‐induced chemical and physical modifications of H2O, CH4, CO, and CO2ions are used. The erosion rates of water ice and the darkening of organic ices on the surfaces of the moons are estimated from the orbit‐integrated fluxes. Significant darkening of fresh organic ices to depths of the order of a micron is expected to occur for times as short as a few thousand years. Darkening at deeper depths will occur at increasingly longer times. The implications of these results for the interpretation of remote sensing data from such objects are discussed.

Urine reagent strips have been used to test cerebrospinal fluid (CSF) in areas where laboratory facilities are unavailable. Protein, glucose and leukocyte esterase patches have been shown to be useful in this context. We propose that the nitrite patch also has a contribution to make: it could provide clinically useful information, at no extra cost. We tested CSF samples from 200 children with suspected meningitis. In a pragmatic approach chosen to reflect the clinical dilemma of whether or not to use parenteral antibiotics, the final laboratory diagnosis was dichotomized into either ‘bacterial meningitis'or ‘not bacterial meningitis’. These diagnostic categories were compared with nitrite patch results, which were either positive or negative. Nitrite patch testing of all CSF, clear CSF and bloody CSF gave positive likelihood ratios of 49, ‘infinity'and 5.8, respectively.

A very important observation1regarding the plasma physics of the outer heliosphere has been that plasma-wave instruments on both the Voyager 1 and 2 spacecraft beyond ∼ 12 AU detected, during the same interval of time, plasma waves (frequency ∼3 kHz) that could possibly be associated with the turbulence expected at the heliopause. It was suggested that this turbulence had propagated inwards to the spacecraft, which would place the heliosphere boundary at ∼46 AU. To interpret these unusual observations, it is important to understand the characteristics of the interplanetary medium at large heliocentric distances. We draw attention here to the low-energy charged-particle environment in the outer heliosphere during the observations of the unusual plasma-wave signals. These particle data suggest that the outer heliosphere was unusually stable and free of transient shock and particle events for the ∼8 months during the wave observations.

THE suggestion by Toth1that the reported long-period oscillations of the solar atmosphere2,3may be observed as oscillations of the geomagnetic field is an intriguing idea. It was suggested1that the ∼2 h 40 min oscillations found in geomagnetic field data recorded at Tihany, Hungary, could reflect, through one of two possible mechanisms, similar period solar oscillations. In the first the geomagnetic field might have natural oscillations at this frequency that could produce environmental changes in the atmosphere4,5and/or ionosphere and/or magnetosphere that would cause the ground-based telescope observations to reach erroneous conclusions. In the second mechanism the oscillations in the solar atmosphere might produce similar frequency oscillations in the interplanetary magnetic field which, through coupling with the geomagnetic field at 1 AU, would cause similar period variations in the field at the Earth's surface. Such oscillations would be in the range of periods of solar wind fluctuations measured near Earth and often attributed to Alfvén waves6. Regular, periodic variations in the interplanetary magnetic field with a period near that of the reported solar oscillations have not been reported. We have spectral analysed geomagnetic field data on the same days as those published by Toth1using data from our fluxgate magnetometer stations in New Hampshire and in Quebec and data from the conjugate area at Siple Station, Antarctica7.

Vasundhara et al.1and Mahra et al.2have recently reported detections of new saturnian ring systems near 12.5 and 19.5 Saturn radii (Rs), respectively. Lazarus et al.3have previously suggested that one or more tenuous rings may exist between 14 and 19 RS, based on observations of unexplained drops in low-energy plasma ion densities in this region of the magnetosphere by Pioneer 11 and Voyagers 1 and 2. However, Baron and Elliot4have placed a stringent upper limit on the I-band brightness of any material in the region 10–36 Rswest of Saturn. Here we review the Voyagerion and electron data in the energy range 30–1,000 keV as measured by the Low Energy Charged Particle (LECP) experiment. There is no convincing evidence for ring matter outside 10 Rsin these data. Features in the charged particle fluxes in these regions are more readily explained by temporal variations and/or spatial structure unrelated to ring matter, such as the mantle on the dayside5and/or detached plasma sheets6.