90 research outputs found
Stereo block copolymers of L- and D-lactides
Sequential diblock copolymers composed of L- and D-lactic acid residues were synthesized through a living ring-opening polymerization of L- and D-lactide initiated by aluminium tris(2-propanolate). The composition of the block copolymers was varied by changing the reaction conditions and monomer over initiator ratio and confirmed by 1H NMR analysis, molecular weight determination and optical rotation measurements. Molecular weights ranged from 1,3 to 2,0 · 104 with 1,2 < Mw/Mn < 1,4. Stereocomplex formation in all block copolymers was determined using differential scanning calorimetry showing melting temperatures of about 205°C
Millimeter-wave communication system using photonic-based remote antennas for configurable network in dense user environment
Photonic-based millimeter-wave communication systems combined with conventional wireless systems have been proposed for the application in dense user environments like a large football stadium. By utilizing a narrow beam antenna for millimeter-wave asymmetric links, effective communication channels can be obtained
Direct Imaging Explorations for Companions around Mid-Late M Stars from the Subaru/IRD Strategic Program
The Subaru telescope is currently performing a strategic program (SSP) using
the high-precision near-infrared (NIR) spectrometer IRD to search for
exoplanets around nearby mid/late-M~dwarfs via radial velocity (RV) monitoring.
As part of the observing strategy for the exoplanet survey, signatures of
massive companions such as RV trends are used to reduce the priority of those
stars. However, this RV information remains useful for studying the stellar
multiplicity of nearby M~dwarfs. To search for companions around such
``deprioritized" M~dwarfs, we observed 14 IRD-SSP targets using Keck/NIRC2
observations with pyramid wavefront sensing at NIR wavelengths, leading to high
sensitivity to substellar-mass companions within a few arcseconds. We detected
two new companions (LSPM~J1002+1459~B and LSPM~J2204+1505~B) and two new
candidates that are likely companions (LSPM~J0825+6902~B and LSPM~J1645+0444~B)
as well as one known companion. Including two known companions resolved by the
IRD fiber injection module camera, we detected seven (four new) companions at
projected separations between ~au in total. A comparison of the
colors with the spectral library suggests that LSPM~J2204+1505~B and
LSPM~J0825+6902~B are located at the boundary between late-M and early-L
spectral types. Our deep high-contrast imaging for targets where no bright
companions were resolved did not reveal any additional companion candidates.
The NIRC2 detection limits could constrain potential substellar-mass companions
() at 10~au or further. The failure with Keck/NIRC2
around the IRD-SSP stars having significant RV trends makes these objects
promising targets for further RV monitoring or deeper imaging with JWST to
search for smaller-mass companions below the NIRC2 detection limits.Comment: 16 pages, 8 figures, accepted for publication in A
- …