ALBERT

Beschreibung: Gravity data of Ceres returned by NASA's Dawn spacecraft is consistent with a lower density crust of variable thickness overlying a higher density mantle. Crustal thickness variations can affect the long-term, post-impact modification of impact craters on Ceres. Here we show that the unusual morphology of the 280-km diameter crater Kerwan may result from viscous relaxation in an outer layer that thins substantially beneath the crater floor. We propose that such a structure is consistent with either impact-induced uplift of the high-density mantle beneath the crater or from volatile loss during the impact event. In either case, the subsurface structure inferred from the crater morphology is superisostatic, and the mass excess would result in a positive Bouguer anomaly beneath the crater, consistent with the highest-degree gravity data from Dawn. Ceres joins the Moon, Mars, and Mercury in having basin-associated gravity anomalies, although their origin may differ substantially.

Beschreibung: We statistically examined the plasmapause location ( L pp ) under quiet geomagnetic conditions ( K p ≤ 1) using the electron density inferred from the THEMIS spacecraft potential for two-year period (2008 and 2009). 543 L pp samples were identified under steady quiet conditions with K p values ≤ 1 during 12 hours prior to the plasmapause crossing. From our large data set, we determined the medians and means of L pp in L and MLT. They are located near geosynchronous orbit and nearly circular. The L pp medians show a slight bulge located in post-dusk sector. Comparing with previous models, our median or mean L pp is extended ∼1-2 L from the earth than the model L pp along the local time from 0800 to 2400 MLT. That is, L pp locations in the previous models are underestimated during quiet geomagnetic conditions.

Beschreibung: We investigate an electron flux dropout during a weak storm on November 7–8, 2008, with Dst minimum value being −37 nT. During this period, two clear dropouts were observed on GOES-11 〉 2MeV electrons. We also find a simultaneous dropout in the sub-relativistic electrons recorded by THEMIS probes in the outer radiation belt. Using the Radiation Belt Environment (RBE) model, we try to reproduce the observed dropout features in both relativistic and sub-relativistic electrons. We found that there are local time dependences in the dropout for both observation and simulation in sub-relativistic electrons; (1) particle loss begins from nightside and propagates into dayside, and (2) resupply starts from near dawn MLT and propagates into the dayside following electron drift direction. That resupply of the particles might be caused by substorm injections due to enhanced convection. We found a significant precipitation in hundreds keV electrons during the dropout. We observe electromagnetic ion cyclotron (EMIC) and chorus waves both on the ground and in space. We find the drift shells are opened near the beginning of the first dropout. The dropout in MeV electrons at GEO might therefore be initiated due to the magnetopause shadowing and the followed dropout in hundreds keV electrons might be the result of the combination of magnetopause shadowing and precipitation loss into the earth's atmosphere.

Beschreibung: The objective of our study was to investigate sexual reproduction of Daphnia magna associated with mating behaviors and hatching rates, according to different algal food sources. Since a diatom is known to contain more abundant long-chain poly unsaturated fatty acids (PUFAs), we hypothesized that the diatom-consuming D. magna would exhibit more successful reproduction rates. Upon the hypothesis, we designed three experiments using two algal species, a green alga ( Chlorella vulgaris ) and a diatom ( Stephanodiscus hantzschii ). From the results, we found that the mating frequency and copulation duration increased in the treatment with S. hantzschii , resulting in a significant increase of hatching rates of resting eggs. In the other two repetitive mating strategies (e.g., one female vs. multiple males, and one male vs. multiple females), we found that the hatching rates of resting eggs were greater in the S. hantzschii treatment. In addition to the mating strategy, male body size significantly increased in the diatom treatment, hence average diameter of penis was also statistically different among the treatments (greater diameter in the S. hantzschii treatment). To examine the effect of algal food quality, we estimated quantity of fatty acids in the two algal species. Our result showed that S. hantzschii had a higher proportion of long-chain PUFAs than C. vulgaris . Furthermore, a stable isotope analysis revealed that carbon and nitrogen originated from S. hantzschii were more assimilated to D. magna . In summary, our study manifested that diatom consumption of D. magna leads to more successful sexual reproduction. We then discussed how the diatom consumption of zooplankton influences food web dynamics in a freshwater ecosystem. Algal food quality is important for daphniids’ sexual reproduction, and the grazers’ sexual reproduction activity are strongly enhanced when a diatom was consumed than a green alga.

Beschreibung: The 1,1,1,2-tetrafluoroethane (HFC-134a), an important alternative to CFC-12 in accordance with the Montreal Protocol on Substances that Deplete the Ozone Layer, is a high Global Warming Potential (GWP) greenhouse gas. Here we evaluate variations in global and regional HFC-134a emissions and emission trends, from 1995 to 2010, at a relatively high spatial and temporal (3.75° in longitude × 2.5° in latitude and 8-day) resolution, using surface HFC-134a measurements. Our results show a progressive increase of global HFC-134a emissions from 19 ± 2 Gg/yr in 1995 to 167 ± 5 Gg/yr in 2010, with both a slowdown in developed countries and a 20 %/yr increase in China since 2005. A seasonal cycle is also seen since 2002, which becomes enhanced over time, with larger values during the boreal summer.

Beschreibung: Tnnt2, encoding thin-filament sarcomeric protein cardiac troponin T, plays critical roles in heart development and function in mammals. To develop an inducible genetic deletion strategy in myocardial cells, we generated a new Tnnt2:MerCreMer ( Tnnt2 MerCreMer/+ ) knock-in mouse. Rosa26 reporter lines were used to examine the specificity and efficiency of the inducible Cre recombinase. We found that Cre was specifically and robustly expressed in the cardiomyocytes at embryonic and adult stages following tamoxifen induction. The knock-in allele on Tnnt2 locus does not impact cardiac function. These results suggest that this new Tnnt2 MerCreMer/+ mouse could be applied towards the temporal genetic deletion of genes of interests in cardiomyocytes with Cre-LoxP technology. The Tnnt2 MerCreMer/+ mouse model also provides a useful tool to trace myocardial lineage during development and repair after cardiac injury. This article is protected by copyright. All rights reserved.

Beschreibung: Plasmaspheric virtual resonance (PVR) model has been proposed as one of source mechanisms for low-latitude Pi2 pulsations. Since PVR-associated Pi2 pulsations are not localized inside the plasmasphere, simultaneous multipoint observations inside and outside the plasmasphere require to test the PVR model. Until now, however, there are few studies using simultaneous multisatellite observations inside and outside the plasmasphere for understanding the radial structure of Pi2 pulsation. In this study, we focus on the Pi2 event observed at low-latitude Bohyun (BOH, L = 1.35) ground station in South Korea in the postmidnight sector (magnetic local time (MLT) = 3.0) for the interval from 1730 to 1900 UT on 12 March 2013. By using electron density derived from the frequency of the upper hybrid waves detected at Van Allen Probe-A (VAP-A) and Van Allen Probe-B (VAP-B), the plasmapause is identified. At the time of the Pi2 event, VAP-A was outside the plasmasphere near midnight (00:55 MLT and L = ~ 6), while VAP-B was inside the plasmasphere in the postmidnight sector (02:15 MLT and L = ~ 5). VAP-B observed oscillations in the compressional magnetic field component ( B z ) and the dawn-to-dusk electric field component ( E y ), having high coherence with the BOH Pi2 pulsation in the H component. The H − B z and H − E y cross phases at VAP-B inside the plasmasphere were near −180° and −90°, respectively.These phase relationships among B z , E y , and H are consistent with a radially standing oscillation of the fundamental mode reported in previous studies. At VAP-A outside the plasmasphere, B z oscillations were highly correlated with BOH Pi2 pulsations with ~−180° phase delay, and the H-E y cross phase is near -90°. From these two-satellite observations, we suggest that the fundamental PVR mode is directly detected by VAP-A and VAP-B.

Beschreibung: The passage of an interplanetary (IP) shock was detected by Wind, ACE, Geotail, and THEMIS-B in the solar wind on 24 November 2008. From the propagation time of the IP shock at the spacecraft, it is expected that the IP shock front is aligned with the Parker spiral and strikes the postnoon dayside magnetopause first. Using multipoint observations of the sudden commencement (SC) at THEMIS probes, GOES 11, and ETS in the dayside magnetosphere, we confirmed that the magnetospheric response to the IP shock starts earlier in the postnoon sector than in the prenoon sector. We found that the estimated normal direction of the SC front is nearly aligned with the estimated IP shock normal. We also found that the SC front normal speed is much slower than the fast mode speed and is about 22–56% of the IP shock speed traveling in the solar wind. Thus, we suggest that the major field changes of the SC in the dayside magnetosphere are not due to the magnetic flux carried by hydromagnetic waves but to the increased solar wind dynamic pressure behind the shock front sweeping the magnetopause. The SC event appears as a step-like increase in the H component at the low-latitude Bohyun station and a negative-then-positive variation in the H component at the high-latitude Chokurdakh (CHD) station in the morning sector. During the negative perturbation at CHD, the SuperDARN Hokkaido radar detected a downward motion in the ionosphere, implying westward electric field enhancement. Using the THEMIS electric field data, it is confirmed that the westward electric field corresponds to the inward plasma motion in the dayside magnetosphere due to the magnetospheric compression.

Beschreibung: We statistically study the local time distribution of the helium band electromagnetic ion cyclotron (EMIC) waves observed at geosynchronous orbit when geomagnetic activity was low ( K p ≤ 1). In order to identify the geosynchronous EMIC waves, we use high-time resolution magnetic field data acquired from GOES 10, 11, and 12 over a two-year period from 2007 and 2008 and examine the local time distribution of EMIC events. Unlike previous studies, which reported high EMIC occurrence in the postnoon sector with a peak around 1500-1600 magnetic local time (MLT) during magnetically disturbed times (i.e., storm and/or substorm), we observed that quiet-time EMIC waves mostly occur in a region from morning (∼0600 MLT) to afternoon (∼1600 MLT) with a peak around 1100-1200 MLT. To investigate whether the quiet-time EMIC wave occurrence has a causal relationship with magnetospheric convection enhancement or solar wind dynamic pressure variations, we performed a superposed epoch analysis of solar wind parameters (solar wind speed, density, dynamic pressure, and IMF B z ) and geomagnetic indices ( A E and S Y M − H ). From the epoch analysis we found that solar wind dynamic pressure variation is more important parameter than A E and S Y M − H for quiet-time EMIC wave occurrence.