The Dimorphos ejecta plume properties revealed by LICIACube.

The Double Asteroid Redirection Test (DART) had an impact with Dimorphos (a satellite of the asteroid Didymos) on 26 September 20221. Ground-based observations showed that the Didymos system brightened by a factor of 8.3 after the impact because of ejecta, returning to the pre-impact brightness 23.7 days afterwards2. Hubble Space Telescope observations made from 15 minutes after impact to 18.5 days after, with a spatial resolution of 2.1 kilometres per pixel, showed a complex evolution of the ejecta3, consistent with other asteroid impact events. The momentum enhancement factor, determined using the measured binary period change4, ranges between 2.2 and 4.9, depending on the assumptions about the mass and density of Dimorphos5. Here we report observations from the LUKE and LEIA instruments on the LICIACube cube satellite, which was deployed 15 days in advance of the impact of DART. Data were taken from 71 seconds before the impact until 320 seconds afterwards. The ejecta plume was a cone with an aperture angle of 140 ± 4 degrees. The inner region of the plume was blue, becoming redder with increasing distance from Dimorphos. The ejecta plume exhibited a complex and inhomogeneous structure, characterized by filaments, dust grains and single or clustered boulders. The ejecta velocities ranged from a few tens of metres per second to about 500 metres per second.

The formation of Charon's red poles from seasonally cold-trapped volatiles.

A unique feature of Pluto's large satellite Charon is its dark red northern polar cap. Similar colours on Pluto's surface have been attributed to tholin-like organic macromolecules produced by energetic radiation processing of hydrocarbons. The polar location on Charon implicates the temperature extremes that result from Charon's high obliquity and long seasons in the production of this material. The escape of Pluto's atmosphere provides a potential feedstock for a complex chemistry. Gas from Pluto that is transiently cold-trapped and processed at Charon's winter pole was proposed as an explanation for the dark coloration on the basis of an image of Charon's northern hemisphere, but not modelled quantitatively. Here we report images of the southern hemisphere illuminated by Pluto-shine and also images taken during the approach phase that show the northern polar cap over a range of longitudes. We model the surface thermal environment on Charon and the supply and temporary cold-trapping of material escaping from Pluto, as well as the photolytic processing of this material into more complex and less volatile molecules while cold-trapped. The model results are consistent with the proposed mechanism for producing the observed colour pattern on Charon.

The geology and geophysics of Kuiper Belt object (486958) Arrokoth.

The Cold Classical Kuiper Belt, a class of small bodies in undisturbed orbits beyond Neptune, is composed of primitive objects preserving information about Solar System formation. In January 2019, the New Horizons spacecraft flew past one of these objects, the 36-kilometer-long contact binary (486958) Arrokoth (provisional designation 2014 MU69). Images from the flyby show that Arrokoth has no detectable rings, and no satellites (larger than 180 meters in diameter) within a radius of 8000 kilometers. Arrokoth has a lightly cratered, smooth surface with complex geological features, unlike those on previously visited Solar System bodies. The density of impact craters indicates the surface dates from the formation of the Solar System. The two lobes of the contact binary have closely aligned poles and equators, constraining their accretion mechanism.

The magnetosphere of uranus: hot plasma and radiation environment.

The low-energy charged-particle (LECP) instrument on Voyager 2 measured lowenergy electrons and ions near and within the magnetosphere of Uranus. Initial analysis of the LECP measurements has revealed the following. (i) The magnetospheric particle population consists principally of protons and electrons having energies to at least 4 and 1.2 megaelectron volts, respectively, with electron intensities substantially excceding proton intensities at a given energy. (ii) The intensity profile for both particle species shows evidence that the particles were swept by planetry satellites out to at least the orbit of Titania. (iii) The ion and electron spectra may be described by a Maxwellian core at low energies (less than about 200 kiloelectron volts) and a power law at high energies (greater than about 590 kiloelectron volts; exponentmicro, 3 to 10) except inside the orbit of Miranda, where power-law spectra (micro approximately 1.1 and 3.1 for electrons and protons, respectively) are observed. (iv) At ion energies between 0.6 and 1 megaelectron volt per nucleon, the composition is dominated by protons with a minor fraction (about 10(-3)) of molecular hydrogen; the lower limit for the ratio of hydrogen to helium is greater than 10(4). (v) The proton population is sufficiently intense that fluences greater than 10(16) per square centimeter can accumulate in 10(4) to 10(') years; such fluences are sufficient to polymerize carbon monoxide and methane ice surfaces. The overall morphology of Uranus' magnetosphere resembles that of Jupiter, as evidenced by the fact that the spacecraft crossed the plasma sheet through the dawn magnetosheath twice per planetary rotation period (17.3 hours). Uranus' magnetosphere differs from that of Jupiter and of Saturn in that the plasma 1 is at most 0.1 rather than 1. Therefore, little distortion ofthe field is expected from particle loading at distances less than about 15 Uranus radii.

Laser altimetry of small-scale features on 433 Eros from NEAR-Shoemaker.

During the Near Earth Asteroid Rendezvous (NEAR)-Shoemaker's low-altitude flyover of asteroid 433 Eros, observations by the NEAR Laser Rangefinder (NLR) have helped to characterize small-scale surface features. On scales from meters to hundreds of meters, the surface has a fractal structure with roughness dominated by blocks, structural features, and walls of small craters. This fractal structure suggests that a single process, possibly impacts, dominates surface morphology on these scales.

Hot Plasma and Energetic Particles in Neptune's Magnetosphere.

The low-energy charged particle (LECP) instrument on Voyager 2 measured within the magnetosphere of Neptune energetic electrons (22 kiloelectron volts /=0.5 MeV per nucleon) energies, using an array of solid-state detectors in various configurations. The results obtained so far may be summarized as follows: (i) A variety of intensity, spectral, and anisotropy features suggest that the satellite Triton is important in controlling the outer regions of the Neptunian magnetosphere. These features include the absence of higher energy (>/=150 keV) ions or electrons outside 14.4 R(N) (where R(N) = radius of Neptune), a relative peak in the spectral index of low-energy electrons at Triton's radial distance, and a change of the proton spectrum from a power law with gamma >/= 3.8 outside, to a hot Maxwellian (kT [unknown] 55 keV) inside the satellite's orbit. (ii) Intensities decrease sharply at all energies near the time of closest approach, the decreases being most extended in time at the highest energies, reminiscent of a spacecraft's traversal of Earth's polar regions at low altitudes; simultaneously, several spikes of spectrally soft electrons and protons were seen (power input approximately 5 x 10(-4) ergs cm(-2) s(-1)) suggestive of auroral processes at Neptune. (iii) Composition measurements revealed the presence of H, H(2), and He(4), with relative abundances of 1300:1:0.1, suggesting a Neptunian ionospheric source for the trapped particle population. (iv) Plasma pressures at E >/= 28 keV are maximum at the magnetic equator with beta approximately 0.2, suggestive of a relatively empty magnetosphere, similar to that of Uranus. (v) A potential signature of satellite 1989N1 was seen, both inbound and outbound; other possible signatures of the moons and rings are evident in the data but cannot be positively identified in the absence of an accurate magnetic-field model close to the planet. Other results indude the absence of upstream ion increases or energetic neutrals [particle intensity (j) < 2.8 x 10(-3) cm(-2) s(-1) keV(-1) near 35 keV, at approximately 40 R(N)] implying an upper limit to the volume-averaged atomic H density at R 22 keV) input on Neptune is approximately 3 x 10(7) W, surprisingly small when compared to energy input into the atmosphere of Jupiter, Saturn, and Uranus.

Pluto's Interaction With Energetic Heliospheric Ions.

Pluto energies of a few kiloelectron volts and suprathermal ions with tens of kiloelectron volts and above. We measure this population using the Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI) instrument on board the New Horizons spacecraft that flew by Pluto in 2015. Even though the measured ions have gyroradii larger than the size of Pluto and the cross section of its magnetosphere, we find that the boundary of the magnetosphere is depleting the energetic ion intensities by about an order of magnitude close to Pluto. The intensity is increasing exponentially with distance to Pluto and reaches nominal levels of the interplanetary medium at about 190R P distance. Inside the wake of Pluto, we observe oscillations of the ion intensities with a periodicity of about 0.2 hr. We show that these can be quantitatively explained by the electric field of an ultralow-frequency wave and discuss possible physical drivers for such a field. We find no evidence for the presence of plutogenic ions in the considered energy range.

Initial results from the New Horizons exploration of 2014 MU69, a small Kuiper Belt object.

The Kuiper Belt is a distant region of the outer Solar System. On 1 January 2019, the New Horizons spacecraft flew close to (486958) 2014 MU69, a cold classical Kuiper Belt object approximately 30 kilometers in diameter. Such objects have never been substantially heated by the Sun and are therefore well preserved since their formation. We describe initial results from these encounter observations. MU69 is a bilobed contact binary with a flattened shape, discrete geological units, and noticeable albedo heterogeneity. However, there is little surface color or compositional heterogeneity. No evidence for satellites, rings or other dust structures, a gas coma, or solar wind interactions was detected. MU69's origin appears consistent with pebble cloud collapse followed by a low-velocity merger of its two lobes.

Surface compositions across Pluto and Charon.

The New Horizons spacecraft mapped colors and infrared spectra across the encounter hemispheres of Pluto and Charon. The volatile methane, carbon monoxide, and nitrogen ices that dominate Pluto's surface have complicated spatial distributions resulting from sublimation, condensation, and glacial flow acting over seasonal and geological time scales. Pluto's water ice "bedrock" was also mapped, with isolated outcrops occurring in a variety of settings. Pluto's surface exhibits complex regional color diversity associated with its distinct provinces. Charon's color pattern is simpler, dominated by neutral low latitudes and a reddish northern polar region. Charon's near-infrared spectra reveal highly localized areas with strong ammonia absorption tied to small craters with relatively fresh-appearing impact ejecta.

The small satellites of Pluto as observed by New Horizons.

The New Horizons mission has provided resolved measurements of Pluto's moons Styx, Nix, Kerberos, and Hydra. All four are small, with equivalent spherical diameters of ~40 kilometers for Nix and Hydra and ~10 kilometers for Styx and Kerberos. They are also highly elongated, with maximum to minimum axis ratios of ~2. All four moons have high albedos (~50 to 90%) suggestive of a water-ice surface composition. Crater densities on Nix and Hydra imply surface ages of at least 4 billion years. The small moons rotate much faster than synchronous, with rotational poles clustered nearly orthogonal to the common pole directions of Pluto and Charon. These results reinforce the hypothesis that the small moons formed in the aftermath of a collision that produced the Pluto-Charon binary.

The Pluto system: Initial results from its exploration by New Horizons.

The Pluto system was recently explored by NASA's New Horizons spacecraft, making closest approach on 14 July 2015. Pluto's surface displays diverse landforms, terrain ages, albedos, colors, and composition gradients. Evidence is found for a water-ice crust, geologically young surface units, surface ice convection, wind streaks, volatile transport, and glacial flow. Pluto's atmosphere is highly extended, with trace hydrocarbons, a global haze layer, and a surface pressure near 10 microbars. Pluto's diverse surface geology and long-term activity raise fundamental questions about how small planets remain active many billions of years after formation. Pluto's large moon Charon displays tectonics and evidence for a heterogeneous crustal composition; its north pole displays puzzling dark terrain. Small satellites Hydra and Nix have higher albedos than expected.

One-week use of ranitidine bismuth citrate, amoxycillin and clarithromycin for the treatment of Helicobacter pylori-related duodenal ulcer.

BACKGROUND: Proton pump inhibitors have been widely used in combination with amoxycillin, clarithromycin or metronidazole for the treatment of Helicobacter pylori infection. AIM: To study the effects of 1-week ranitidine bismuth citrate (RBC)-based triple therapy in the treatment of H. pylori-related duodenal ulcers. METHOD: Patients with duodenal ulcers and H. pylori infection were prospectively randomized to receive either RBC with amoxycillin and clarithromycin for 1 week (RAC), or omeprazole with amoxycillin and clarithromycin for 1 week (OAC). No additional ulcer healing drug was used after the 1-week medication. Patients were assessed for H. pylori eradication, ulcer healing and side-effects after receiving the therapies. RESULTS: One hundred consecutive patients were recruited to this study, with 50 patients randomized to each treatment group. In the intention-to-treat analysis, duodenal ulcers were completely healed in 45 (90%) patients in the RAC group and 43 (89.6%) in the OAC group (P = 1.0). H. pylori eradication was confirmed in 47 (94%) in the RAC group and 42 (87.5%) in the OAC group (P = 0.31). There was no significant difference in the severity of side-effects experienced by the two treatment groups. CONCLUSION: One-week RBC-based triple therapy is an effective treatment for H. pylori-related duodenal ulcers. The therapeutic effects are comparable to a 1-week course of proton pump inhibitor-based triple therapy.

One-week ranitidine bismuth citrate in combinations with metronidazole, amoxycillin and clarithromycin in the treatment of Helicobacter pylori infection: the RBC-MACH study.

BACKGROUND: We have previously shown that ranitidine bismuth citrate (RBC)-based triple therapy is comparable to proton pump inhibitor-based triple therapy in eradicating Helicobacter pylori infection. AIM: To test the efficacy of different combinations of antimicrobials with RBC in the treatment of H. pylori infection. METHODS: Dyspeptic patients with H. pylori infection were prospectively randomized to receive one of the following regimens: (i) RBC 400 mg, amoxycillin 1 g, clarithromycin 500 mg [RAC]; (ii) RBC 400 mg, metronidazole 400 mg, clarithromycin 500 mg [RMC]; (iii) RBC 400 mg, metronidazole 400 mg, tetracycline 1 g [RMT] (all given twice daily for 1 week); or (iv) RBC 400 mg plus clarithromycin 500 mg twice daily for 2 weeks [RC-2]. Endoscopy (rapid urease test and culture) and 13C-urea breath test (UBT) were performed before randomization. Four weeks after finishing medication, the 13C-UBT was repeated in all cases and endoscopy was offered to patients with peptic ulcers. RESULTS: Four hundred patients were randomized but in two (one in the RAC group and one in the RMC group) H. pylori infection was not confirmed. Successful eradication of H. pylori (intention-to-treat analysis and 95% CI) of RAC (86% [79-93%]), RMC (90% [84-96%]), RMT (79% [71-87%]) and RC-2 (82% [75-90%]) were comparable, with a trend favouring clarithromycin-containing triple therapy regimens. Among 276 isolates tested for antibiotic sensitivity, primary resistance to metronidazole, clarithromycin and amoxycillin was found in 56%, 2% and 0.4%, respectively. When given RMC or RMT, patients infected by metronidazole-resistant H. pylori had success in eradicating H. pylori similar to patients infected by metronidazole-sensitive H. pylori. CONCLUSION: One-week RBC triple therapy is effective in curing H. pylori infection.

Use of eyepatches in phototherapy: effects on conjunctival bacterial pathogens and conjunctivitis.

We conducted a randomized controlled trial to determine the effects of eye occlusion on the risk of eye infection in full term newborn infants receiving phototherapy. Among 102 infants whose eyes were occluded with eyepatches, pathogens were isolated from 50 eyes of 33 infants. The positive isolation rate was significantly higher than that of a group of control infants (n = 101) whose eyes were protected by a headbox made of light-proof plastics. Among the latter group pathogens were detected in 22 eyes of 14 infants. In addition significantly more infants in the eyepatches group had purulent eye discharge (23 of 102 vs. 9 of 101, P = 0.013) and clinical conjunctivitis (13 of 102 vs. 2 of 101, P = 0.004) than the controls. Proper eye care is imperative when eyepatches are used on infants receiving phototherapy, and alternative methods of eye protection should be considered.

The use of CHROMagar Orientation as a primary isolation medium with presumptive identification for the routine screening of urine specimens.

The aim of the study was to compare the use of a novel differential culture medium CHROMagar, for both primary isolation and presumptive identificaton, with the method currently used in our laboratory for screening mid-stream-urine samples (MSU). Routine methods (RM) included blotting paper imprinting of all specimens and additional quantitative culture on cysteine lactose electrolyte-deficient agar (CLED) for selected samples together with Microbact 12E for further identification. The CHROMagar method (CH) relied on the use of blotting paper imprints, colonial colour and morphology on CHROMagar only. With respect to the 3390 MSU specimens examined, both methods yielded similar results in 3240, including > or = 87% of Escherichia coli, Pseudomonas spp., Staphylococcus spp., Proteus mirabilis/Morganella morganii and Enterobacter/Serratia/Klebsiella/Citrobacter spp. Of the 52 discordant identifications, yeasts were reported as staphylococci on CHROMagar in 10. The overall cost of materials per specimen was US$ 0.30 by RM and $ 0.24 by CH. It took about 3 min to perform each Microbact test. Thus, CHROMagar plus Gram stain and other simple bench tests gave results similar to those using our current method, but had the advantage of saving time and materials.

Human herpesvirus-6 encephalitis after unrelated umbilical cord blood transplant in children.

Three children developed human herpesvirus-6 (HHV-6), variant B encephalitis after unrelated umbilical cord blood transplant, in a single center. They developed clinical manifestations of encephalitis around day 17 post transplant. Impairment of consciousness, incoherent speech, episodic focal pruritus, motor weakness, convulsions and severe hyponatremia were features at presentation. Radiological investigation of brain ranged from unremarkable to extensive white matter and meningeal lesions. Diagnosis was established by the presence of HHV-6 DNA in cerebrospinal fluid (CSF). Retrospective analyses of plasma revealed the presence of viral DNAemia prior to the onset of disease in two subjects. Treatment with ganciclovir or foscarnet was given. Two subjects did not achieve engraftment and died of other transplant-related complications on day 38 and 56 post-transplant, respectively. One subject achieved disease-free survival for more than 1 year with a satisfactory neurological outcome. In conclusion, HHV-6 encephalitis is not uncommon among patients undergoing umbilical cord blood transplantation. It is worth conducting further studies on early diagnosis and optimal management of this potentially fatal disease.

A longitudinal analysis of methicillin-resistant Staphylococcus aureus in a Hong Kong teaching hospital.

OBJECTIVES: To review the incidence and trends of MRSA during a 12-year (1989-2000) period at a university teaching hospital and the relationship between strain distribution by antibiogram and molecular typing. DESIGN: Retrospective review of laboratory-based surveillance records on MRSA isolation and characterization of strains by antimicrobial susceptibility and PFGE. A patient episode was counted at the time when MRSA was first isolated. SETTING: A 1,350-bed university teaching hospital in Hong Kong. PATIENTS: Those with clinical isolates of MRSA. RESULTS: During 1989 to 2000, the hospital recorded 1,203,175 deaths and discharges (D&D) and encountered 5,707 patient episodes of new MRSA isolation. The overall incidence of patient episodes of MRSA was 0.47/100 D&D. In 1989, the incidence was 0.81/100 D&D and fell to a low of 0.33/100 D&D in 1995, but then rose to 0.50/100 D&D in 2000. Antibiogram and DNA typing identified 5 major types. PFGE type A constituted 68% (211/312) of isolates and was present throughout the 12-year period. PFGE type B constituted 13% (40/312) of isolates and was only present from 1995 to 2000. These isolates form a distinct clone and had unique antibiotic resistance profiles. CONCLUSIONS: The study showed the establishment of a dominant MRSA clone (PFGE type A group) in the intensive care, medical, and surgical units and the appearance of a new MRSA strain in 1995 (PFGE type B), which partly explained the rise in incidence of MRSA cases and a disproportionate rise in MRSA bacteremia from 1995 to 2000.

Living with methicillin-resistant Staphylococcus aureus: a 7-year experience with endemic MRSA in a university hospital.

A review of our infection control records revealed 3,159 new isolations of methicillin-resistant Staphylococcus aureus (MRSA) from 1988 to 1994. Prior to this period, our approach to MRSA had changed from eradication to containment measures. We found a decline in MRSA rates from 11.4 to 5.2 first isolations per 1,000 deaths and discharges over the study period.

Waterhouse-Friderichsen syndrome complicating primary biliary sepsis due to Pasteurella multocida in a patient with cirrhosis.

Pasteurella multocida is an opportunistic pathogen causing bacteraemia in patients with liver dysfunction. A fulminant case of acute cholecystitis and septicaemia caused by P multocida, complicated by Waterhouse-Friderichsen syndrome without skin haemorrhage, is reported in a previously healthy 64 year old Chinese woman. The patient presented with a six hour history of sudden onset epigastric pain, vomiting, chills, and rigors. A presumptive diagnosis of cholangitis with septicaemic shock was made. Disease progression was rapid and the patient died within eight hours of symptom onset. This case is further proof that skin and mucosal haemorrhages are not an essential feature of Waterhouse-Friderichsen syndrome and this condition should be suspected in all patients presenting with sudden illness and fulminant septicaemia.

Detection of human herpesviruses 6 and 7 genomic sequences in brain tumours.

BACKGROUND: Human herpesviruses 6 and 7 (HHV-6, HHV-7) are ubiquitous, with primary infection occurring early in life followed by persistence, which may involve neural tissue. While HHV-6 and HHV-7 are predominantly T lymphotropic, the extent of tissue tropism in persistent infection is not known. AIM: To investigate neuropersistence and the role of HHV-6 and HHV-7 in brain tumorigenesis. METHODS: Nested polymerase chain reaction was used to detect HHV-6 and HHV-7 genomic sequences in preparations of total DNA extracted from 98 formalin fixed, paraffin embedded primary brain tumours. HHV-6 detected was further characterized into variants A and B by restriction fragment length analysis. RESULTS: HHV-6 was detected in 8.2% of cases and HHV-7 in 14.3% (14/98). None of the positive samples contained both viruses. Among the eight HHV-6 positive tumours, three harboured variant A and five variant B. Four of the five ependymomas studied contained viral DNA. Otherwise, both HHV-6 and HHV-7 were present at similar low frequencies in most of the tumour types investigated. CONCLUSIONS: The findings do not support an aetiological role of HHV-6 and HHV-7 in primary brain tumour, but they suggest that HHV-6 and HHV-7 are neurotropic in vivo and that the central nervous system seems to be one of the reservoirs for persistent infection.