1,043 research outputs found
Enantioselective synthesis of N-benzylic heterocycles: a nickel and photoredox dual catalysis approach
Reported herein is a dual nickel- and photoredox-catalyzed modular approach for the preparation of enantioenriched N-benzylic heterocycles. α-Heterocyclic carboxylic acids, easily obtainable from common commercial material, are reported as suitable substrates for a decarboxylative strategy in conjunction with a chiral pyridine–oxazoline (PyOx) ligand, providing quick access to enantioenriched drug-like products. The presence of a directing group on the heterocyclic moiety is shown to be beneficial, affording improved stereoselectivity in a number of cases
Ages and Metallicities of Star Clusters and Surrounding Fields in the Outer Disk of the Large Magellanic Cloud
We present Washington system C,T_1 CMDs of 13 star clusters and their
surrounding fields which lie in the outer parts of the LMC disk. Ages are
determined by means of the magnitude difference between the giant branch clump
and the turnoff, while metallicities are derived from the location of the giant
and subgiant branches as compared to fiducial star clusters. We find that in
most cases the stellar population of each star cluster is quite similar to that
of the field where it is embedded. Three particular fields present remarkable
properties: (i) The so far unique cluster ESO121-SC03 at ~9 Gyr has a
surrounding field which shares the same properties. (ii) The field surrounding
the far eastern intermediate age cluster OHSC37 is noteworthy in the sense that
we do not detect any evidence of LMC stars. (iii) The fields of SL388 and SL509
present CMDs with a secondary clump ~0.45 mag fainter than the dominant
intermediate age clump, suggesting a stellar population component located
behind the LMC disk at a distance comparable to that of the SMC. The mean
metallicity derived for the intermediate age outer disk clusters is
=-0.7 and for their surrounding fields =-0.6. These values are
significantly lower than found by Olszewski et al. (1991, AJ, 101, 515) for a
sample of clusters of similar age, but are in good agreement with several
recent studies. A few clusters stand out in the age--metallicity relation in
the sense that they are intermediate age clusters at relatively low metallicity
([Fe/H]~-1).Comment: LaTeX, to be published in July, 1998 Astronomical Journa
TSS-1 - Orbiter current and voltage experiments
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76697/1/AIAA-1993-702-280.pd
Questions concerning tyrosine kinase-inhibitor therapy and transplants in chronic phase chronic myeloid leukaemia
In this provocative commentary, we consider several questions posed by the late chronic myeloid leukaemia (CML) expert Prof. Michele Baccarani, which he challenged us to address after his death. He noted only a small proportion of people with chronic phase CML receiving tyrosine kinase-inhibitor (TKI)-therapy are likely to achieve sustained therapy-free remission (TFR) and even fewer are likely to be cured. Persons most likely to fail TKItherapy can be identified at diagnosis or soon after starting TKI-therapy. These persons are likely to need lifetime TKI-therapy with attendant risks of adverse events, cost and psychological consequences. Allogeneic transplants achieve much higher rates of leukaemia-free survival compared with TKI-therapy but are associated with transplant-related adverse events including an almost 20 percent risk of transplant-related deaths within 1 year post-transplant and a compromised quality-of-life because of complications such as chronic graft-versus-host disease. Subject-, disease- and transplant-related co-variates associated with transplant outcomes are known with reasonable accuracy. Not everyone likely to fail TKI-therapy is a transplant candidate. However, in those who candidates are physicians and patients need to weigh benefits and risks of TKI-therapy versus a transplant. We suggest transplants should be more often considered in the metric when counseling people with chronic phase CML unlikely to achieve TFR with TKI-therapy. We question whether we are discounting a possible important therapy intervention; we think so
The current‐voltage characteristics of a large probe in low Earth orbit: TSS‐1R results
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95277/1/grl10536.pd
The MIDAS experiment: A prototype for the microwave emission of Ultra-High Energy Cosmic Rays
Recent measurements suggest that extensive air showers initiated by
ultra-high energy cosmic rays (UHECR) emit signals in the microwave band of the
electromagnetic spectrum caused by the collisions of the free-electrons with
the atmospheric neutral molecules in the plasma produced by the passage of the
shower. Such emission is isotropic and could allow the detection of air showers
with 100% duty cycle and a calorimetric-like energy measurement, a significant
improvement over current detection techniques. We have built MIDAS (MIcrowave
Detection of Air Showers), a prototype of microwave detector, which consists of
a 4.5 m diameter antenna with a cluster of 53 feed-horns in the 4 GHz range.
The details of the prototype and first results will be presented.Comment: To appear in the proceedings of 12th Topical Seminar on Innovative
Particle and Radiation Detectors (IPRD10), Siena, Italy, 7 - 10 June 201
Shuttle charging by tether controlled electron beam
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95327/1/grl10600.pd
Cerenkov emissions of ion acoustic‐like waves generated by electron beams emitted during TSS 1R
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95646/1/grl10913.pd
{BOAO Photometric Survey of Galactic Open Clusters. II. Physical Parameters of 12 Open Clusters
We have initiated a long-term project, the BOAO photometric survey of open
clusters, to enlarge our understanding of galactic structure using UBVI CCD
photometry of open clusters which have been little studied before. This is the
second paper of the project in which we present the photometry of 12 open
clusters. We have determined the cluster parameters by fitting the Padova
isochrones to the color-magnitude diagrams of the clusters. All the clusters
except for Be 0 and NGC 1348 are found to be intermediate-age to old (0.2 - 4.0
Gyrs) open clusters with a mean metallicity of [Fe/H] = 0.0.Comment: 11 page
Novel Potent Muscarinic Receptor Antagonists: Investigation on the Nature of Lipophilic Substituents in the 5- and/or 6-Positions of the 1,4-Dioxane Nucleus
A series of novel 1,4-dioxane analogues of the muscarinic acetylcholine receptor (mAChR) antagonist 2 was synthesized and studied for their affinity at M1-M5 mAChRs. The 6-cyclohexyl-6-phenyl derivative 3b, with a cis configuration between the CH2N+(CH3)3 chain in the 2-position and the cyclohexyl moiety in the 6-position, showed pKi values for mAChRs higher than those of 2 and a selectivity profile analogous to that of the clinically approved drug oxybutynin. The study of the enantiomers of 3b and the corresponding tertiary amine 33b revealed that the eutomers are (2S,6S)-(-)-3b and (2S,6S)-(-)-33b, respectively. Docking simulations on the M3 mAChR-resolved structure rationalized the experimental observations. The quaternary ammonium function, which should prevent the crossing of the blood-brain barrier, and the high M3/M2 selectivity, which might limit cardiovascular side effects, make 3b a valuable starting point for the design of novel antagonists potentially useful in peripheral diseases in which M3 receptors are involved
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