ALBERT

Description: Cell sheet engineering has been developed as an alternative approach to improve mesenchymal stem cell-mediated tissue regeneration. In this study, we found that vitamin C (Vc) was capable of inducing telomerase activity in periodontal ligament stem cells (PDLSCs), leading to the up-regulated expression of extracellular matrix type I collagen, fibronectin, and integrin β1, stem cell markers Oct4, Sox2, and Nanog as well as osteogenic markers RUNX2, ALP, OCN. Under Vc treatment, PDLSCs can form cell sheet structures because of increased cell matrix production. Interestingly, PDLSC sheets demonstrated a significant improvement in tissue regeneration compared with untreated control dissociated PDLSCs and offered an effective treatment for periodontal defects in a swine model. In addition, bone marrow mesenchymal stem cell sheets and umbilical cord mesenchymal stem cell sheets were also well constructed using this method. The development of Vc-mediated mesenchymal stem cell sheets may provide an easy and practical approach for cell-based tissue regeneration. J. Cell. Physiol. © 2011 Wiley Periodicals, Inc.

Description: Abstract In situ aircraft measurements obtained during the RACORO field campaign are analyzed to study the aerosol effects on different cloud regimes. The results show that with increasing cloud condensation nuclei (CCN), cloud droplet number concentration (Nd) significantly increases in stratocumulus (Sc) while remains almost unchanged in cumulus (Cu). By using a new approach to strictly constrain the dynamics in Cu, we found that neither simultaneously changing cloud dynamics nor dilution of cloud water induced by entrainment‐mixing can explain the observed insensitivity of Nd. The different degree of reduction in cloud supersaturation caused by increasing aerosols might be responsible for the observed different aerosol indirect effect between Sc and Cu.

Description: In this paper, presented for the first time the three-dimensional global morphology and seasonal variations of scintillation index (S4 index) measured from the signal-to-noise ratio (SNR) intensity fluctuations of L1 channel of GPS radio occultation (RO) signals using FORMOSAT-3/COSMIC (in short, F3/C) satellites for a low solar activity year 2008. The S4 index, which confined around ±30° magnetic latitudes, is found to start around post-sunset hours (1900 MLT, magnetic local time) and often persists till post-midnight hours (0300 MLT) between 150 and 350 km altitudes during equinox and northern winter seasons while no activity is observed during southern winter season. However, high latitudes are characterized with no scintillation activity beyond 150 km during any season, which implying that in the solar minimum period the drives of instabilities in the auroral, cusp and polar cap regions, namely the gradient drift and velocity shear, are absent. The S4 index at F region altitudes during magnetically quiet times is more intense and extends to higher latitudes than that observed during disturbed time consistent with earlier studies. The equatorial S4 index appears below the peak of F2 layer (hmF2) during most of the seasons although the associated intensities and the time of maximum occurrences are relatively higher and earlier during vernal equinox followed by autumn equinox. This equinoctial asymmetry could be primarily attributed to the asymmetries in eastward drift velocities, thermospheric meridional winds and plasma densities. Further, the global maps of S4 index at E region altitudes (between 75 and 125 km) show strong seasonal variations with highest activity during northern and southern summer solstice in the middle latitudes while it appears on both sides of magnetic equator with less or no activity at and around the equator during equinox seasons. The absence of S4 index along the equator can be understood in terms of the vanishing vertical component of the magnetic field lines that can inhibit the vertical movement and layered deposition of ionized particles of thin irregular electron density layers such as Es-layers. Keeping in view the importance of these valuable database, we would like to emphasize that the F3/C GPS RO technique can be used to study the ionospheric irregularities at GHz frequency globally directly from the high-rate L1 data, which reiterating its importance as a powerful tool to explore the terrestrial ionosphere on a global scale.

Description: Methanol to olefin process was investigated over a steam-treated Ca-ZSM-5 catalyst in a flow-type fixed bed reactor by adding aromatics to the methanol feed. As a comparison, the catalytic performance in the presence of nitrogen and water was also investigated. The experimental results exhibit that in the presence of aromatics, the total light olefin selectivity and the ethylene selectivity increased, while propylene selectivity increased with adding o- xylene and m -xylene to the methanol feed, but decreased with adding benzene, toluene, p -xylene and ethylbenzen to the methanol feed. The catalyst was characterized by temperature-programmed desorption of ammonia, N 2 adsorption, and scanning electron microscope. The adsorption of water and aromatics on the catalyst was also studied. Based on the results, it is concluded that aromatics may be responsible for the formation of light olefins and be more favorable for ethylene than propylene in methanol conversion. The methanol to olefin process was investigated over a steam-treated Ca-ZSM-5 catalyst in a flow-type fixed bed reactor by adding aromatics to the methanol feed. High light-olefin selectivity was gained. Further experimental data suggested that aromatics enhanced the formation of light olefins in methanol conversion.

Description: The neutral mass density N and electron density Ne at 400 km height measured by CHAMP during nine intense geomagnetic storms bring out some new aspects of the thermospheric and ionospheric storms. The thermospheric storms (increase of N) develop with the onset of the main phases (MP) of the geomagnetic storms and reach their peak phases before or by the end of the MPs. The ionospheric storms (change of Ne) in general undergo an initial negative phase (with the equatorial ionization anomaly (EIA) crests shifting poleward) before turning positive, and the positive storms reach their peak strengths (or phases) centered at ±25°–30° magnetic latitudes; in some (4) cases the positive storms develop without an initial negative phase and with the EIA crests shifting equatorward; in all cases the positive storms reach their peak phases before the end of the MPs and turn to conventional negative storms by the end of the MPs. The observations agree with the different aspects of a physical mechanism of the positive storms. The observations also reveal that the Halloween storms of 30 October 2003 with a short MP without fluctuations produced the strongest positive ionospheric storms through impulsive response, and there is strong equinoctial asymmetry in the ionosphere and thermosphere during geomagnetic storms.

Description: It has been predicted that the Moon's shadow, the cooling region, sweeping over the Earth's atmosphere with a supersonic speed could trigger bow waves since 1970. The longest total solar eclipse within next hundred years occurring on 22 July 2009 sweeps over the Eastern Asia region during the noontime period. An analysis of the Hilbert-Huang transform (HHT) is applied to study ionospheric TEC (total electron content) derived from ground-based GPS receivers in Taiwan and Japan. We not only find the feature of the predicted bow wave but also the stern wave on the equator side of the eclipse path, as well as the stern wake right behind the Moon's shadow boat. The bow and stern waves are formed by acoustic gravity waves of periods about 3 and/or 5 minutes traveling equatorward with a phase speed of about 100 m/s in the ionosphere.

Description: Analysis of the dayside electron density (Ne) and neutral mass density (N) at 400 km height measured by CHAMP during 12 intense geomagnetic storms in 2000–2004, and ion densities at 600 km and 840 km heights measured by ROCSAT and DMSP during a few of the intense storms, reveal some new aspects. Thermospheric storms (change of N) reach the equator within 1.5 to 3 hours from the main phase (MP) onset of intense storms having short and steady MPs. The responses of the equatorial ionosphere (at CHAMP) to both MPs and RPs (recovery phases) of the storms are generally opposite to those at higher latitudes. In addition to the known opposite responses during MPs, the analysis reveals that positive ionospheric storms develop at equatorial latitudes (within about ±15° magnetic latitudes) during daytime RPs, while conventional negative storms occur at higher latitudes. Ionospheric storms also extend to the topside ionosphere beyond 850 km height and are generally positive (at DMSP), especially during MPs. The positive storms around the equatorial ionospheric peak during RPs are interpreted in terms of the potential sources such as (1) zero or westward electric fields due to disturbance dynamo and/or prompt penetration, (2) plasma convergence due to the mechanical effects of storm-time equatorward neutral winds and waves, (3) increase of atomic oxygen density and decrease of molecular nitrogen density due to the downwelling effect of the winds, and (4) photoionization. The positive storms in the topside ionosphere during MPs involve the rapid upward drift of plasma due to eastward PPEFs, reduction in the downward diffusion of plasma along the field lines, and plasma convergence due to equatorward winds and waves.

Description: Abstract Using data from the MMS mission and the First‐Order Taylor Expansion (FOTE) method, here we reveal electron distribution functions around a reconnection X‐line at the Earth's magnetopause. We find cigar distribution of electrons in both the magnetosphere‐side and magnetosheath‐side inflow regions, isotropic distribution of electrons at the separatrix, and loss of high‐energy electrons in the antiparallel direction in the magnetosheath‐side inflow region. We interpret the formation of cigar distribution in the inflow regions using the Fermi mechanism—as suggested in previous simulations, the loss of high‐energy electrons in the magnetosheath side using the parallel electric fields—which evacuate electrons to escape the diffusion region along the antiparallel direction, and the isotropic distribution at the separatrix using the pitch angle scattering by whistler waves—which exist frequently at the separatrix. We also find that the electron distribution functions can change rapidly (within 60 ms) from isotropic to cigar as the spacecraft moves slightly away from the separatrix.

Description: Niobium aluminum carbide ( Nb 4 AlC 3 ), as a member of the MAX phases, can retain its stiffness and strength up to over 1400°C, however, the strength at room temperature is relatively low. In this work, Nb 5 ( Si , Al ) 3 was used to strengthen Nb 4 AlC 3 . Nb 4 AlC 3 – Nb 5 ( Si , Al ) 3 composites with different amount of Nb 5 ( Si , Al ) 3 were synthesized from the elemental powders by in situ hot-pressing/solid–liquid reaction synthesis process. The RT flexural strength was significantly improved from 370 MPa of monolithic Nb 4 AlC 3 to 432 MPa of Nb 4 AlC 3 -15 vol% Nb 5 ( Si , Al ) 3 composite without the degradation of its high-temperature mechanical properties. While a slightly decrease in fracture toughness occurs with the increment of Nb 5 ( Si , Al ) 3 content. Meanwhile, Transmission electron microscopy (TEM) observations reveal that the interfaces between Nb 4 AlC 3 / Nb 4 AlC 3 , Nb 4 AlC 3 / Nb 5 ( Si , Al ) 3 , and Nb 5 ( Si , Al ) 3 / Nb 5 ( Si , Al ) 3 are free of amorphous layers, which is also beneficial to its high-temperature mechanical properties.

Description: Abstract Recently, interplanetary shocks have been reported to cause ``electron dropout echoes” in the outer radiation belt, which is manifested as repeated dropout and recovery signals in electron fluxes. Both previous case and statistical studies have shown that electron dropout echoes are mostly found for high‐energy (〉300 keV) electrons, and the initial dropout region is mainly located at the dusk magnetosphere, regardless of shock parameters such as shock normal. To understand these properties, we model the electron dropout echoes at geosynchronous orbit by tracing electrons in the analytic field model of the shock‐induced propagating pulse. It is shown that the characteristics of shock‐induced electron dropout echo events including energy‐dependence and localization are well reproduced by our model. By analyzing the trajectories of typical electrons, we find that electrons are inward transported and accelerated through ``drift‐resonance‐like” interactions with the magnetosonic pulse. Two causes of the dawn‐dusk asymmetric response are presented: (1) the difference between the interaction time of electrons with the magnetosonic pulse and (2) the opposite radial ∇ B drift of the electrons at dawnside and duskside. Further, we calculate the contributions to electron dynamics and phase space density variations from three terms: E×B drift, radial ∇B drift and gyro‐betatron acceleration. The details of electron flux variations could vary with the form of the shock‐induced pulse and the initial electron distribution, thus be different from our results; however, the basic ingredients of the electron interaction with the pulse could provide a general frame for understanding and evaluating electron flux responses.