Forty-five years after the Apollo and Luna missions returned the lunar samples, China's Chang’E-5 (CE-5) mission collected new samples from the mid-latitude region in the northeastern Oceanus Procellarum of the Moon. Our study shows that 95% of CE-5 lunar soil is distributed in the size of 1.40–9.35 μm, while 95% of the soil by mass is distributed in the size of 4.84–432.27 μm. The bulk density, true density, and specific surface area of CE-5 soil are 1.2387 g/cm3, 3.1952 g/cm3, and 0.56 m2/g, respectively. Fragments from CE-5 regolith are classified into igneous clasts (mostly basalt), agglutinate, and glass. A few breccias were also found. The minerals and compositions of CE-5 soils are consistent with mare basalts and can be classified as low-Ti/low-Al/low-K type with lower rare earth element (REE) contents than materials rich in potassium, rare earth element, and phosphorus (KREEP). CE-5 soils have high FeO and low Mg index, which could represent a new class of basalt.

No abstract

Influenza vaccines based on conserved antigens could provide cross-protection against infections by multiple subtypes of influenza A virus. Influenza matrix protein 2 (M2) is highly conserved in all influenza A strains. In this study, we deleted the transmembrane domain of the M2 of the avian influenza virus (AIV) A/Chicken/Jiangsu/7/2002 (H9N2) strain to create an M2 without a transmembrane domain, named sM2, which was efficiently expressed in Escherichia coli. The sM2 protein was administered intranasally to mice in combination with chitosan adjuvant three times at an interval of 3 weeks. Three weeks after the last immunization, the mice were challenged with a lethal dose (5 x LD(50)) of A/Chicken/Jiangsu/7/2002 (H9N2) virus, PR8 (H1N1) virus and A/Chicken/Henan/12/2004 (H5N1) virus. The protective immunity of the vaccine was evaluated by determining the survival rates, residual lung virus titers, body weight, and the serum antibody titers of the mice. Nasal administration of 15 microg sM2 in combination with chitosan completely protected mice against the homologous virus and protected 90 and 30% of the mice against the heterologous H1N1 and H5N1 viruses, respectively. The study indicated that the sM2 protein was a candidate antigen for a broad-spectrum influenza virus vaccine and that the adjuvant chitosan improved the efficacy of the sM2 vaccine.

We report the new measurement of initial current pulses in rocket‐triggered lightning with a broadband magnetic sensor at 78 m distance. The high sensitivity of our sensor makes it possible to detect weak ripple deflections (as low as 0.4 A) that are not readily resolved in the typical measurements of channel‐base current in rocket‐triggered lightning experiments. The discernible magnetic pulses within 1 ms after the inception of a sustained upward positive leader from the triggering wire can be classified into impulsive pulses and ripple pulses according to the discernibility of separation between individual pulses. The time scale (usually >20 µs) of ripple pulses is substantially longer than the leading impulsive pulses (with time scales typically <10 µs), and the amplitude is significantly reduced, whereas there is no considerable difference in the interpulse pulse. Along with our previous finding on the burst of magnetic pulses during the initial continuous current in rocket‐triggered lightning, the new measurements suggest that the stepwise propagation might be a persistent feature for the upward positive leader in rocket‐triggered lightning, and the stepping of positive leader early in triggered lightning could be characterized with the observation of ripple pulses. The precedence of impulsive magnetic pulse measured at 78 m range relative to the arrival of corresponding current pulse at the channel base indicates that the ionization wave launched by individual stepping of positive leader propagates downward along the triggering wire at a mean velocity of 1.23 × 108 m/s to 2.25 × 108 m/s.

Two cases of bidirectional leader, starting almost immediately below a decaying dart or dart‐stepped leader which terminated before reaching the ground, were identified, for the first time, in rocket‐triggered lightning flashes based on high‐speed video, electric field changes, and channel base current, indicating that a bidirectional leader can be excited by a decayed dart leader and propagate in a preexisting discharge channel. The positive end of the bidirectional leader moved upward along the terminated downward dart leader path, and the negative end extended downward along the decayed initial continuous current or preceding stroke path to the ground and culminated in a return stroke. The positive leader propagated with an average speed of 1.3 × 106 m/s and 2.2 × 106 m/s in the two cases, roughly twice as fast as its negative counterpart with speed of 7.8 × 105 m/s and 1.0 × 106 m/s, respectively. The positive end started earlier than the negative end with a preceding time less than 40.3 µs. The bidirectional leader can be regarded as a recoil leader with the positive end retrogressing along a negative leader channel, whose polarity is contrary to the traditional recoil leader with negative leader end retrogressing along an existing positive leader channel. Weak luminosity was continuously observed during the terminated dart leader and bidirectional leader stage, but the channel current was less than the minimum detection capability of 9.3 A.

A negative lightning flash with 16 leader-return stroke sequences, triggered in the summer of 2013 using the classical rocket-and-wire triggering technique, was examined with simultaneous two-dimensional (2D) imaging of very high-frequency (VHF) radiation sources, channel-base current measurement, broadband electric field waveforms and high-speed video images. A total of 28.0 C negative charge was transferred to ground during the whole flash, and the charge transferred during the initial stage was 4.9 C, which is the weakest among the triggered lightning flashes at the SHandong Artificially Triggering Lightning Experiment (SHATLE). The peak current of 16 return strokes ranged from 5.8 to 32.5 kA with a geometric mean of 14.1 kA. The progression of upward positive leader and downward negative (dart or dart-stepped) leaders was reproduced visually by using an improved short-baseline VHF lightning location system with continuous data recording capability. The upward positive leader was mapped immediately from the tip of the metal wire during the initial stage, developing at a speed of about 10 4 m/s without branches. The upward positive leader and all the 14 negative leaders captured by the 2D imaging system propagated along the same channel with few branches inside the cloud, which might be the reason for the relatively small charge transfer. The 2D imaging results also show that dart leaders may transform into dart-stepped leaders after a long time interval between successive strokes.

No abstract

How lightning initiates inside thunderclouds remains a major puzzle of atmospheric electricity. By monitoring optical emissions from thunderstorms, the Atmosphere‐Space Interactions Monitor (ASIM) onboard the International Space Station is providing new clues about lightning initiation by detecting Blue LUminous Events (BLUEs), which are manifestations of electrical corona discharges that sometimes precedes lightning. Here we combine optical and radio observations from a thunderstorm near Malaysia to uncover a new type of event containing multiple optical and radio pulses. We find that the first optical pulse coincides with a strong radio signal in the form of a Narrow Bipolar Event (NBE) but subsequent optical pulses, delayed some milliseconds, have weaker radio signals, possibly because they emanate from a horizontally oriented electrical discharges which does not trigger full‐fledged lightning. Our results cast light on the differences between isolated and lightning‐initiating electrical discharges.