509 research outputs found
Giant enhancement of cryogenic thermopower by polar structural instability in the pressurized semimetal MoTe2
We found that a high mobility semimetal 1T'-MoTe2 shows a significant
pressure-dependent change in the cryogenic thermopower in the vicinity of the
critical pressure, where the polar structural transition disappears. With the
application of a high pressure of 0.75 GPa, while the resistivity becomes as
low as 10 {\mu}{\Omega}cm, thermopower reached the maximum value of 60
{\mu}VK-1 at 25 K, leading to a giant thermoelectric power factor of 300
{\mu}WK-2cm-1. Based on semiquantitative analyses, the origin of this behavior
is discussed in terms of inelastic electron-phonon scattering enhanced by the
softening of zone center phonon modes associated with the polar structural
instability.Comment: 13 pages, 4 figures Physical review B (accepted
Structure, function, and evolution of plant NIMA-related kinases: implication for phosphorylation-dependent microtubule regulation
icrotubules are highly dynamic structures that control the spatiotemporal pattern of cell growth and division. Microtubule dynamics are regulated by reversible protein phosphorylation involving both protein kinases and phosphatases. Never in mitosis A (NIMA)-related kinases (NEKs) are a family of serine/threonine kinases that regulate microtubule-related mitotic events in fungi and animal cells (e.g. centrosome separation and spindle formation). Although plants contain multiple members of the NEK family, their functions remain elusive. Recent studies revealed that NEK6 of Arabidopsis thaliana regulates cell expansion and morphogenesis through β-tubulin phosphorylation and microtubule destabilization. In addition, plant NEK members participate in organ development and stress responses. The present phylogenetic analysis indicates that plant NEK genes are diverged from a single NEK6-like gene, which may share a common ancestor with other kinases involved in the control of microtubule organization. On the contrary, another mitotic kinase, polo-like kinase, might have been lost during the evolution of land plants. We propose that plant NEK members have acquired novel functions to regulate cell growth, microtubule organization, and stress responses
Estimation of the detected background by the future gamma ray transient mission CAMELOT
This study presents a background estimation for the CubeSats Applied for MEasuring and LOcalising Transients (CAMELOT), which is a proposed fleet of nanosatellites for the all-sky monitoring and timing-based localization of gamma ray transients with precise localization capability at low Earth orbits. CAMELOT will allow us to observe and precisely localize short gamma ray bursts (GRBs) associated with kilonovae, long GRBs associated with core-collapse massive stars, magnetar outbursts, terrestrial gamma ray flashes, and gamma ray counterparts to gravitational wave sources. A fleet of at least nine 3U CubeSats is proposed to be equipped with large and thin CsI(Tl) scintillators read out by multipixel photon counters (MPPC). A careful study of the radiation environment in space is necessary to optimize the detector casing, estimate the duty cycle due to the crossing of the South Atlantic Anomaly and polar regions, and minimize the effect of the radiation damage of MPPCs
Characterization of FOXSI Sounding Rocket Hard X-Ray Detectors Using Advanced Light Source at Berkeley
No abstract availabl
On the faintest solar coronal hard X-rays observed with FOXSI
Solar nanoflares are small eruptive events releasing magnetic energy in the
quiet corona. If nanoflares follow the same physics as their larger
counterparts, they should emit hard X-rays (HXRs) but with a rather faint
intensity. A copious and continuous presence of nanoflares would deliver
enormous amounts of energy into the solar corona, possibly accounting for its
high temperatures. To date, there has not been any direct observation of such
sustained and persistent HXRs from the quiescent Sun. However, Hannah et al. in
2010 constrained the quiet Sun HXR emission using almost 12 days of quiescent
solar-off-pointing observations by RHESSI. These observations set upper limits
at photons s cm keV and
photons s cm keV for the 3-6
keV and 6-12 keV energy ranges, respectively. Observing feeble HXRs is
challenging because it demands high sensitivity and dynamic range instruments
in HXRs. The Focusing Optics X-ray Solar Imager (FOXSI) sounding rocket
experiment excels in these two attributes. Particularly, FOXSI completed its
third successful flight (FOXSI-3) on September 7th, 2018. During FOXSI-3's
flight, the Sun exhibited a fairly quiet configuration, displaying only one
aged non-flaring active region. Using the entire 6.5 minutes of FOXSI-3
data, we constrained the quiet Sun emission in HXRs. We found upper
limits in the order of photons s cm
keV for the 5-10 keV energy range. FOXSI-3's upper limit is consistent
with what was reported by Hannah et al., 2010, but FOXSI-3 achieved this result
using 1/2640 less time than RHESSI. A possible future spacecraft using
FOXSI's concept would allow enough observation time to constrain the current
HXR quiet Sun limits further or perhaps even make direct detections
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