805 research outputs found
Photometric defocus observations of transiting extrasolar planets
We have carried out photometric follow-up observations of bright transiting
extrasolar planets using the CbNUOJ 0.6m telescope. We have tested the
possibility of obtaining high photometric precision by applying the telescope
defocus technique allowing the use of several hundred seconds in exposure time
for a single measurement. We demonstrate that this technique is capable of
obtaining a root-mean-square scatter of order sub-millimagnitude over several
hours for a V 10 host star typical for transiting planets detected from
ground-based survey facilities. We compare our results with transit
observations with the telescope operated in in-focus mode. High photometric
precision is obtained due to the collection of a larger amount of photons
resulting in a higher signal compared to other random and systematic noise
sources. Accurate telescope tracking is likely to further contribute to
lowering systematic noise by probing the same pixels on the CCD. Furthermore, a
longer exposure time helps reducing the effect of scintillation noise which
otherwise has a significant effect for small-aperture telescopes operated in
in-focus mode. Finally we present the results of modelling four light-curves
for which a root-mean-square scatter of 0.70 to 2.3 milli-magnitudes have been
achieved.Comment: 12 pages, 11 figures, 5 tables. Submitted to Journal of Astronomy and
Space Sciences (JASS
Design principles for transforming making programs into online settings at public libraries
Purpose This paper aims to investigate design principles for transforming existing making communities of practice within public libraries into online knowledge-building communities to support youths, families with young children and adult membersâ making and tinkering during COVID-19. Design/methodology/approach Building upon C4P and connected learning framework, the authors analyze existing literature and practitioner reports on informal learning projects related to making and STEM learning, family learning and online learning as well as emergent cases of innovative approaches in response to COVID-19 from public libraries, informal learning institutions and community groups. Findings The authors suggest 11 design principles around five areas: program design, facilitation, tools and materials, process documentation and sharing and feedback. Originality/value This work contributes to the information and learning sciences concerned with community engagement and knowledge creation by suggesting a design model to transform and sustain existing making communities of practice within public libraries into online knowledge-building communities during COVID-19
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Reversible Anionic Redox Activities in Conventional LiNi1/3 Co1/3 Mn1/3 O2 Cathodes.
Redox reactions of oxygen have been considered critical in controlling the electrochemical properties of lithium-excessive layered-oxide electrodes. However, conventional electrode materials without overlithiation remain the most practical. Typically, cationic redox reactions are believed to dominate the electrochemical processes in conventional electrodes. Herein, we show unambiguous evidence of reversible anionic redox reactions in LiNi1/3 Co1/3 Mn1/3 O2 . The typical involvement of oxygen through hybridization with transition metals is discussed, as well as the intrinsic oxygen redox process at high potentials, which is 75â% reversible during initial cycling and 63â% retained after 10â
cycles. Our results clarify the reaction mechanism at high potentials in conventional layered electrodes involving both cationic and anionic reactions and indicate the potential of utilizing reversible oxygen redox reactions in conventional layered oxides for high-capacity lithium-ion batteries
Prolonged Activation of ERK Contributes to the Photorejuvenation Effect in Photodynamic Therapy in Human Dermal Fibroblasts
Photodynamic therapy (PDT) is known to be effective in the photorejuvenation of photoaged skin. However, the molecular mechanisms of rejuvenation by PDT remain elusive. In this study, we aimed to understand the molecular events occurring during the photorejuvenation after PDT in dermal fibroblasts in vitro. First, we found that PDT conditions resulted in an increased fibroblast proliferation and motility in vitro. Under this condition, cells had increased intracellular reactive oxygen species (ROS) production. Importantly, PDT induced a prolonged activation of extracellular signalâregulated kinase (ERK) with a corresponding increase in matrix metalloproteinase (MMP)-3 and collagen type Iα messenger RNA and protein. Moreover, inhibition of PDT-induced ERK activation significantly suppressed fibroblast proliferation and expression of MMP-3 and collagen type Iα following PDT. In addition, NAC (an antioxidant) inhibited PDT-induced fibroblast proliferation and ERK activation indicating that prolonged ERK activation and intracellular ROS contribute to the proliferation of fibroblasts and the dermal remodeling process for skin rejuvenation. We also identified increased collagen volume and decreased elastotic materials that are used as markers of photoaging in human skin samples using histochemical studies. Results from this study suggest that intracellular ROS stimulated by PDT in dermal fibroblasts lead to prolonged activation of ERK and, eventually, fibroblast proliferation and activation. Our data thus reveal a molecular mechanism underlying the skin rejuvenation effect of PDT
Shortâterm effects of neoadjuvant chemoradiation therapy on anorectal function in rectal cancer patients: a pilot study
A soft, transparent, freely accessible cranial window for chronic imaging and electrophysiology
Chronic in vivo imaging and electrophysiology are important for better understanding of neural functions and circuits. We introduce the new cranial window using soft, penetrable, elastic, and transparent, silicone-based polydimethylsiloxane (PDMS) as a substitute for the skull and dura in both rats and mice. The PDMS can be readily tailored to any size and shape to cover large brain area. Clear and healthy cortical vasculatures were observed up to 15âweeks post-implantation. Real-time hemodynamic responses were successfully monitored during sensory stimulation. Furthermore, the PDMS window allowed for easy insertion of microelectrodes and micropipettes into the cortical tissue for electrophysiological recording and chemical injection at any location without causing any fluid leakage. Longitudinal two-photon microscopic imaging of Cx3Cr1+/â GFP transgenic mice was comparable with imaging via a conventional glass-type cranial window, even immediately following direct intracortical injection. This cranial window will facilitate direct probing and mapping for long-term brain studies.112121sciescopu
Comparison of the Two Followup Observation Strategies for Gravitational Microlensing Planet Searches
There are two different strategies of followup observations for the detection
of planets by using microlensing. One is detecting the light curve anomalies
affected by the planetary caustic from continuous monitoring of all events
detected by microlensing survey programs (type I strategy) and the other is
detecting anomalies near the peak amplification affected by the central caustic
from intensive monitoring of high amplification events (type II strategy). It
was shown by Griest & Safizadeh that the type II strategy yields high planet
detection efficiency per event. However, it is not known the planet detection
rate by this strategy can make up a substantial fraction of the total rate. In
this paper, we estimate the relative planet detection rates expected under the
two followup observation strategies. From this estimation, we find that the
rate under the type II strategy is substantial and will comprise --
1/2 of the total rate. We also find that compared to the type I strategy the
type II strategy is more efficient in detecting planets located outside of the
lensing zone. We determine the optimal monitoring frequency of the type II
strategy to be times/night, which can be easily achieved by the
current microlensing followup programs even with a single telescope.Comment: total 5 pages, including 3 figures and 1 table, ApJ, submitte
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