1,882 research outputs found
Spiro[1H-azulenium-1,9 '-fluorene] perchlorate. Intramolecular charge-transfer interaction between orthogonally arranged units of the azulenium cation and fluorene
ArticleTETRAHEDRON LETTERS. 49(49): 7058-7061 (2008)journal articl
Detection of lithium in nearby young late-M dwarfs
Late M-type dwarfs in the solar neighborhood include a mixture of very
low-mass stars and brown dwarfs which is difficult to disentangle due to the
lack of constraints on their age such as trigonometric parallax, lithium
detection and space velocity.
We search for young brown dwarf candidates among a sample of 28 nearby late-M
dwarfs with spectral types between M5.0 and M9.0, and we also search for debris
disks around three of them.
Based on theoretical models, we used the color , the -band absolute
magnitude and the detection of the Li I 6708 doublet line as a strong
constraint to estimate masses and ages of our targets. For the search of debris
disks, we observed three targets at submillimeter wavelength of 850 m.
We report here the first clear detections of lithium absorption in four
targets and a marginal detection in one target. Our mass estimates indicate
that two of them are young brown dwarfs, two are young brown dwarf candidates
and one is a young very low-mass star. The closest young field brown dwarf in
our sample at only 15 pc is an excellent benchmark for further studying
physical properties of brown dwarfs in the range 100150 Myr. We did not
detect any debris disks around three late-M dwarfs, and we estimated upper
limits to the dust mass of debris disks around them.Comment: 10 pages, 5 figures, accepted for publication in Astronomy and
Astrophysic
Synthesis and stability of 1,1-dialkyl-1H-azulenium cations
ArticleTETRAHEDRON. 62(34): 8177-8183 (2006)journal articl
Synthesis, Stability, and Crystal Structure of an Azulenium Cation Containing an Adamantyl Group
This is the pre-peer reviewed version of the following article: EUROPEAN JOURNAL OF ORGANIC CHEMISTRY. 2008(31):5301-5307 (2008), which has been published in final form at doi:10.1002/ejoc.200800700.ArticleEUROPEAN JOURNAL OF ORGANIC CHEMISTRY. 2008(31):5301-5307 (2008)journal articl
Solar models and solar neutrino oscillations
We provide a summary of the current knowledge, theoretical and experimental,
of solar neutrino fluxes and of the masses and mixing angles that characterize
solar neutrino oscillations. We also summarize the principal reasons for doing
new solar neutrino experiments and what we think may be learned from the future
measurements.Comment: Submitted to the Neutrino Focus Issue of New Journal of Physics at
http://www.njp.or
Magnetic and Magnetotransport Properties of La0.7ca0.3mn1-x(zn,cu)xo3
Magnetic and magnetotransport properties of two perovskite manganite samples of La0.7Ca0.3Mn0.9Zn0.1O3 and La0.7Ca0.3Mn0.95Cu0.05O3 prepared by conventional solid-state reaction have been studied in detail. Experimental results revealed that the temperature dependences of magnetization and resistance varied strongly around the phase-transition temperature. Maximum magnetoresistance (MR) values of La0.7Ca0.3Mn0.9Zn0.1O3 and La0.7Ca0.3Mn0.95Cu0.05O3 under an applied field of 400 Oe were about 21.4 % and 11.0 %, respectively. The maximum magnetic-entropy change (ΔSM) was 2.73 J/kg.K for La0.7Ca0.3Mn0.9Zn0.1O3, and 3.34 J/kg.K for La0.7Ca0.3Mn0.95Cu0.05O3 when the applied field was 45 kOe. Both the MR and ΔSM values obtained from two samples were smaller than those of the parent compound La0.7Ca0.3MnO3. This was due to the change in the Mn3+/Mn4+ ratio caused by Zn and Cu dopants, which led to a change in the type of the ferromagneticparamagnetic phase transition
q-Deformation of W(2,2) Lie algebra associated with quantum groups
An explicit realization of the W(2,2) Lie algebra is presented using the
famous bosonic and fermionic oscillators in physics, which is then used to
construct the q-deformation of this Lie algebra. Furthermore, the quantum group
structures on the q-deformation of this Lie algebra are completely determined.Comment: 12 page
Discovering Valuable Items from Massive Data
Suppose there is a large collection of items, each with an associated cost
and an inherent utility that is revealed only once we commit to selecting it.
Given a budget on the cumulative cost of the selected items, how can we pick a
subset of maximal value? This task generalizes several important problems such
as multi-arm bandits, active search and the knapsack problem. We present an
algorithm, GP-Select, which utilizes prior knowledge about similarity be- tween
items, expressed as a kernel function. GP-Select uses Gaussian process
prediction to balance exploration (estimating the unknown value of items) and
exploitation (selecting items of high value). We extend GP-Select to be able to
discover sets that simultaneously have high utility and are diverse. Our
preference for diversity can be specified as an arbitrary monotone submodular
function that quantifies the diminishing returns obtained when selecting
similar items. Furthermore, we exploit the structure of the model updates to
achieve an order of magnitude (up to 40X) speedup in our experiments without
resorting to approximations. We provide strong guarantees on the performance of
GP-Select and apply it to three real-world case studies of industrial
relevance: (1) Refreshing a repository of prices in a Global Distribution
System for the travel industry, (2) Identifying diverse, binding-affine
peptides in a vaccine de- sign task and (3) Maximizing clicks in a web-scale
recommender system by recommending items to users
Synthesis and properties of 2-(2-pyridyl)-1-azaazulene
ArticleTETRAHEDRON LETTERS. 48(26): 4471-4475 (2007)journal articl
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