Archetypal analysis of galaxy spectra

Archetypal analysis represents each individual member of a set of data vectors as a mixture (a constrained linear combination) of the pure types or archetypes of the data set. The archetypes are themselves required to be mixtures of the data vectors. Archetypal analysis may be particularly useful in analysing data sets comprising galaxy spectra, since each spectrum is, presumably, a superposition of the emission from the various stellar populations, nebular emissions and nuclear activity making up that galaxy, and each of these emission sources corresponds to a potential archetype of the entire data set. We demonstrate archetypal analysis using sets of composite synthetic galaxy spectra, showing that the method promises to be an effective and efficient way to classify spectra. We show that archetypal analysis is robust in the presence of various types of noise.Comment: 6 pages, 5 figures, 1 style-file. Accepted for publication by MNRA

Mass Hierarchy, Mixing, CP-Violation and Higgs Decay---or Why Rotation is Good for Us

The idea of a rank-one rotating mass matrix (R2M2) is reviewed detailing how it leads to ready explanations both for the fermion mass hierarchy and for the distinctive mixing patterns between up and down fermion states, which can be and have been tested against experiment and shown to be fully consistent with existing data. Further, R2M2 is seen to offer, as by-products: (i) a new solution of the strong CP problem in QCD by linking the theta-angle there to the Kobayashi-Maskawa CP-violating phase in the CKM matrix, and (ii) some novel predictions of possible anomalies in Higgs decay observable in principle at the LHC. A special effort is made to answer some questions raised.Comment: 47 pages, 9 figure

Facile O-atom insertion into C-C and C-H bonds by a trinuclear copper complex designed to harness a singlet oxene

Two trinuclear copper [CuICuICuI(L)]1+ complexes have been prepared with the multidentate ligands (L) 3,3'-(1,4-diazepane-1,4-diyl)bis(1-((2-(dimethylamino)ethyl)(methyl)amino)propan-2-ol) (7-Me) and (3,3'-(1,4-diazepane-1,4-diyl)bis(1-((2-(diethylamino) ethyl)(ethyl) amino)propan-2-ol) (7-Et) as models for the active site of the particulate methane monooxygenase (pMMO). The ligands were designed to form the proper spatial and electronic geometry to harness a "singlet oxene," according to the mechanism previously suggested by our laboratory. Consistent with the design strategy, both [CuICuICuI(L)]1+ reacted with dioxygen to form a putative bis(µ3-oxo)CuIICuIICuIII species, capable of facile O-atom insertion across the central C-C bond of benzil and 2,3-butanedione at ambient temperature and pressure. These complexes also catalyze facile O-atom transfer to the C-H bond of CH3CN to form glycolonitrile. These results, together with our recent biochemical studies on pMMO, provide support for our hypothesis that the hydroxylation site of pMMO contains a trinuclear copper cluster that mediates C-H bond activation by a singlet oxene mechanism

Archetypal Analysis: Mining Weather and Climate Extremes

Conventional analysis methods in weather and climate science (e.g., EOF analysis) exhibit a number of drawbacks including scaling and mixing. These methods focus mostly on the bulk of the probability distribution of the system in state space and overlook its tail. This paper explores a different method, the archetypal analysis (AA), which focuses precisely on the extremes. AA seeks to approximate the convex hull of the data in state space by finding “corners” that represent “pure” types or archetypes through computing mixture weight matrices. The method is quite new in climate science, although it has been around for about two decades in pattern recognition. It encompasses, in particular, the virtues of EOFs and clustering. The method is presented along with a new manifold-based optimization algorithm that optimizes for the weights simultaneously, unlike the conventional multistep algorithm based on the alternating constrained least squares. The paper discusses the numerical solution and then applies it to the monthly sea surface temperature (SST) from HadISST and to the Asian summer monsoon (ASM) using sea level pressure (SLP) from ERA-40 over the Asian monsoon region. The application to SST reveals, in particular, three archetypes, namely, El Niño, La Niña, and a third pattern representing the western boundary currents. The latter archetype shows a particular trend in the last few decades. The application to the ASM SLP anomalies yields archetypes that are consistent with the ASM regimes found in the literature. Merits and weaknesses of the method along with possible future development are also discussed

In-vivo magnetic resonance imaging of hyperpolarized silicon particles

Silicon-based micro and nanoparticles have gained popularity in a wide range of biomedical applications due to their biocompatibility and biodegradability in-vivo, as well as a flexible surface chemistry, which allows drug loading, functionalization and targeting. Here we report direct in-vivo imaging of hyperpolarized 29Si nuclei in silicon microparticles by MRI. Natural physical properties of silicon provide surface electronic states for dynamic nuclear polarization (DNP), extremely long depolarization times, insensitivity to the in-vivo environment or particle tumbling, and surfaces favorable for functionalization. Potential applications to gastrointestinal, intravascular, and tumor perfusion imaging at sub-picomolar concentrations are presented. These results demonstrate a new background-free imaging modality applicable to a range of inexpensive, readily available, and biocompatible Si particles.Comment: Supplemental Material include

Hyperfine Interactions and Spin Transport in Ferromagnet-Semiconductor Heterostructures

Measurements and modeling of electron spin transport and dynamics are used to characterize hyperfine interactions in Fe/GaAs devices with $n$-GaAs channels. Ga and As nuclei are polarized by electrically injected electron spins, and the nuclear polarization is detected indirectly through the depolarization of electron spins in the hyperfine field. The dependence of the electron spin signal on injector bias and applied field direction is modeled by a coupled drift-diffusion equation, including effective fields from both the electronic and nuclear polarizations. This approach is used to determine the electron spin polarization independently of the assumptions made in standard transport measurements. The extreme sensitivity of the electron spin dynamics to the nuclear spin polarization also facilitates the electrical detection of nuclear magnetic resonance.Comment: Submitted to Phys. Rev.