398 research outputs found
Esters of (S)-1,2-propanediol and (R,R)-2,3-butanediol â Chiral Compounds Inducing Cholesteric Phases with a Helix Inversion ·
Mesogenic chiral esters of optically active (S)-1,2-propanediol and (R,R)-2,3-butanediol were synthesized. The compounds, added to a nematic phase induce cholesteric phases exhibiting a helix inversion with temperature variation. This effect is independent of the molecular structure of the nematic solvent. The inversion temperature varies only slightly with concentration but can be influenced by the mesogenic substituent
The distance to the LMC cluster NGC 1866 and the surrounding field
We use the Main Sequence stars in the LMC cluster NGC 1866 and of Red Clump
stars in the local field to obtain two independent estimates of the LMC
distance. We apply an empirical Main Sequence-fitting technique based on a
large sample of subdwarfs with accurate {\sl Hipparcos} parallaxes in order to
estimate the cluster distance modulus, and the multicolor Red Clump method to
derive distance and reddening of the LMC field. We find that the Main
Sequence-fitting and the Red Clump distance moduli are in significant
disagreement; NGC 1866 distance is equal to 0.08 (consistent with a previous estimate using the same data
and theoretical Main Sequence isochrones), while the field stars provide 0.07. This difference reflects the more general
dichotomy in the LMC distance estimates found in the literature. Various
possible causes for this disagreement are explored, with particular attention
paid to the still uncertain metallicity of the cluster and the star formation
history of the field stars.Comment: 5 pages, incl. 1 figure, uses emulateapj.sty, ApJ accepte
RuddlesdenâPopper hybrid lead bromide perovskite nanosheets of phase pure n=2: Stabilized colloids stored in the solid state
Ruddlesden-Popper lead halide perovskite (RP-LHP) nano-nanostructures can be regarded as self-assembled quantum wells or superlattices of 3D perovskites with an intrinsic quantum well thickness of a single or a few (n=2-4) lead halide layers; the quantum wells are separated by organic layers. They can be scaled down to a single quantum well dimension. Here, the preparation of highly (photo)chemical and colloidal stable hybrid LHP nanosheets (NSs) of ca. 7.4 ”m lateral size and 2.5 nm quantum well height (thereby presenting a deep blue emission at ca. 440 nm), is reported for the first time. The NSs are close-lying and they even interconnect when deposited on a substrate. Their synthesis is based on the use of the p-toluenesulfonic acid/dodecylamine (pTS/DDA) ligand pair and their (photo)chemical stability and photoluminescence is enhanced by adding EuBr2 nanodots (EuNDs). Strikingly, they can be preserved as a solid and stored for at least one year. The blue emissive colloid can be recovered from the solid as needed by simply dispersing the powder in toluene and then using it to prepare solid films, making them very promising candidates for manufacturing devices. © 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH
Distances, ages, and epoch of formation of globular clusters
We review the results on distances and absolute ages of galactic globular
clusters (GCs) obtained after the release of the Hipparcos catalogue. Several
methods for the Population II local distance scale are discussed, exploiting
NEW RESULTS for RR Lyraes in the Large Magellanic Cloud (LMC). We find that the
so-called Short and Long Distance Scales may be reconciled whether a consistent
reddening scale is adopted for Cepheids and RR Lyrae variables in the LMC.
Distances and ages for the 9 clusters discussed in Paper I are re-derived using
an enlarged sample of local subdwarfs, which includes about 90% of the
metal-poor dwarfs with accurate parallaxes (Delta p/p < 0.12) in the whole
Hipparcos catalogue. On average, our revised distance moduli are decreased by
0.04 mag with respect to Paper I. The corresponding age of the GCs is
t=11.5+-2.6 Gyr (95% confidence range). The relation between Mv(ZAHB) and
metallicity for the nine programme clusters turns out to be
Mv(ZAHB)=(0.18+-0.09)([Fe/H]+1.5)+(0.53+-0.12).Thanks to Hipparcos the major
contribution to the total error budget associated with the subdwarf fitting
technique has been moved from parallaxes to photometric calibrations, reddening
and metallicity scale. This total uncertainty still amounts to about +-0.12
mag. Comparing the corresponding (true) LMC distance modulus 18.64+-0.12 mag
with other existing determinations, we conclude that at present the best
estimate for the distance of the LMC is: 18.54+-0.03+-0.06, suggesting that
distances from the subdwarf fitting method are 1 sigma too long. Consequently,
our best estimate for the age of the GCs is revised to: Age = 12.9+-2.9 Gyr
(95% confidence range). The best relation between Mv(ZAHB) and [Fe/H] is:
Mv(ZAHB) =(0.18+-0.09)([Fe/H]+1.5)+(0.63+-0.07).Comment: 76 pages, 6 encapsulated figures and 6 tables. Latex, uses
aasms4.sty. Revised and improved version, with new data on field RR Lyraes in
LMC. Accepted in the Astrophysical Journa
Lightcurves of Type Ia Supernovae from Near the Time of Explosion
We present a set of 11 type Ia supernova (SN Ia) lightcurves with dense,
pre-maximum sampling. These supernovae (SNe), in galaxies behind the Large
Magellanic Cloud (LMC), were discovered by the SuperMACHO survey. The SNe span
a redshift range of z = 0.11 - 0.35. Our lightcurves contain some of the
earliest pre-maximum observations of SNe Ia to date. We also give a functional
model that describes the SN Ia lightcurve shape (in our VR-band). Our function
uses the "expanding fireball" model of Goldhaber et al. (1998) to describe the
rising lightcurve immediately after explosion but constrains it to smoothly
join the remainder of the lightcurve. We fit this model to a composite observed
VR-band lightcurve of three SNe between redshifts of 0.135 to 0.165. These SNe
have not been K-corrected or adjusted to account for reddening. In this
redshift range, the observed VR-band most closely matches the rest frame
V-band. Using the best fit to our functional description of the lightcurve, we
find the time between explosion and observed VR-band maximum to be
17.6+-1.3(stat)+-0.07(sys) rest-frame days for a SN Ia with a VR-band Delta
m_{-10} of 0.52mag. For the redshifts sampled, the observed VR-band
time-of-maximum brightness should be the same as the rest-frame V-band maximum
to within 1.1 rest-frame days.Comment: 35 pages, 18 figures, 15 tables; Higher quality PDF available at
http://ctiokw.ctio.noao.edu/~sm/sm/SNrise/index.html; AJ accepte
Synthesis, characterization and benzene oxidation promoted by a new mononuclear copper(II) complex, [Cu(BTMEA)2Cl]Cl
The Distances of the Magellanic Clouds
The present status of our knowledge of the distances to the Magellanic Clouds
is evaluated from a post-Hipparcos perspective. After a brief summary of the
effects of structure, reddening, age and metallicity, the primary distance
indicators for the Large Magellanic Cloud are reviewed: The SN 1987A ring,
Cepheids, RR Lyraes, Mira variables, and Eclipsing Binaries. Distances derived
via these methods are weighted and combined to produce final "best" estimates
for the Magellanic Clouds distance moduli.Comment: Invited review article to appear in ``Post Hipparcos Cosmic
Candles'', F. Caputo & A. Heck (Eds.), Kluwer Academic Publ., Dordrecht, in
pres
Fundamental Insights into the Covalent Silane Functionalization of NiFe Layered Double Hydroxides
Layered double hydroxides (LDHs) are a class of 2D anionic materials exhibiting wide chemical versatility and promising applications in different fields ranging from catalysis to energy storage and conversion. However, the covalent chemistry of this kind of 2D materials is still barely explored. Herein, we report the covalent functionalization with silanes of a magnetic NiFe-LDH. The synthetic route consists of a topochemical approach followed by the anion exchange reaction of a surfactant molecules prior to the covalent functionalization with the (3- aminopropyl)triethoxysilane (APTES) molecules. The functionalized NiFe-APTES was fully characterized using X-ray diffraction, infrared spectroscopy, electron microscopy, thermogravimetric analysis coupled with mass spectrometry and 29Si solid state nuclear magnetic resonance, among others. The effect on the electronic properties of the functionalized LDH was studied by a magnetic study in combination with Mössbauer spectroscopy. Moreover, the reversibility of the silane-functionalization at basic pH was demonstrated, and the quality of the resulting LDH proved by studying the electrochemical performance in the oxygen evolution reaction in basic media. Furthermore, the anion exchange capability for the NiFe-APTES was tested employing Cr(VI), resulting in an increase of 200 % of the anion retention. This report allows a new level in the tunability of LDHs opening the door to the synthesis of new hybrid materials and architectures
Marketing madness or financial folly?: Implementing equity crowdfunding in the record industry
Purpose The purpose of this paper is to explore the implementation of equity crowdfunding (ECF) within the record industry in terms of challenges and opportunities, in addition to the marketing and financial implications for independent music artists and major record labels. Design/methodology/approach This study adopted a qualitative methodology consisting of two-stage interview-based research methods. A total of 44 semi-structured in-depth interviews were conducted with the CEOs of ECF platforms in the record industry, other related record industry informants, independent artist managers and senior executives from major record labels. Findings The loyalty aspect of ECF may have significant marketing potential in terms of inconspicuously using the equity platform as a âprosumerâ identification mechanism. As this early career stage of artists is delicate in terms of establishing trust and patronage from their fans, these early marketing and ECF ventures should be implemented directly from the artist without external third-party involvement. Research limitations/implications The implications of this paperâs findings and theoretical model are not limited to the two studied stakeholder groups of the record industry. The insights in relation to the obstinate lack of understanding and clarity (particularly for independent artists) which surround ECF are likely to influence short-term strategic approaches by other players throughout the wider music industry. Practical implications The insights regarding negative approaches towards ECF by the labels may influence future âcoopetition strategiesâ for independent labels, as they seek to navigate the changing industry dynamics. Originality/value This paper is the first study to empirically explore the predominantly under-researched area of ECF implementation in the record industry in terms of marketing and financial consequences for artists and labels. </jats:sec
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