Stein factors for negative binomial approximation in Wasserstein distance

The paper gives the bounds on the solutions to a Stein equation for the negative binomial distribution that are needed for approximation in terms of the Wasserstein metric. The proofs are probabilistic, and follow the approach introduced in Barbour and Xia (Bernoulli 12 (2006) 943-954). The bounds are used to quantify the accuracy of negative binomial approximation to parasite counts in hosts. Since the infectivity of a population can be expected to be proportional to its total parasite burden, the Wasserstein metric is the appropriate choice.Comment: Published at http://dx.doi.org/10.3150/14-BEJ595 in the Bernoulli (http://isi.cbs.nl/bernoulli/) by the International Statistical Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm

Dynamic response of strongly correlated Fermi gases in the quantum virial expansion

By developing a quantum virial expansion theory, we quantitatively calculate the dynamic density response function of a trapped strongly interacting Fermi gas at high temperatures near unitarity. A clear transition from atomic to molecular responses is identified in the spectra when crossing from the BCS to BEC regimes, in qualitative agreement with recent Bragg spectroscopy observations. Our virial expansion method provides a promising way to solve the challenging strong-coupling problems and is applicable to other dynamical properties of strongly correlated Fermi gases.Comment: 5 pages, 4 figures; published version in Phys. Rev. A. The quantum virial expansion of single-particle spectral function is discussed in arXiv:1003.1538 (Phys. Rev. Lett. 104, 240407 (2010)

On Stein‘s factors for Poisson approximation in Wasserstein distance

We provide a probabilistic proof of various Stein's factors for Poisson approximation in terms of the Wasserstein distance

Efficient Synthesis of Narrowly Dispersed Brush Copolymers and Study of Their Assemblies: The Importance of Side Chain Arrangement

Efficient, one-pot preparation of synthetically challenging, high molecular weight (MW), narrowly dispersed brush block copolymers and random copolymers in high conversions was achieved by ring-opening metathesis (co)polymerization (ROMP) of various macromonomers (MMs) using the highly active, fast-initiating ruthenium olefin metathesis catalyst (H_2IMes)(pyr)_2(Cl)_2RuCHPh. A series of random and block copolymers were prepared from a pair of MMs containing polylactide (PLA) and poly(n-butyl acrylate) (PnBA) side chains at similar MWs. Their self-assembly in the melt state was studied by small-angle X-ray scattering (SAXS) and atomic force microscopy (AFM). In brush random copolymers containing approximately equal volume fractions of PLA and PnBA, the side chains segregate into lamellae with domain spacing of 14 nm as measured by SAXS, which was in good agreement with the lamellar thickness measured by AFM. The domain spacings and order−disorder transition temperatures of brush random copolymers were insensitive to the backbone length. In contrast, brush block copolymers containing approximately equal volume fractions of these MMs self-assembled into highly ordered lamellae with domain spacing over 100 nm. Their assemblies suggested that the brush block copolymer backbone adopted an extended conformation in the ordered state

Performance of Halbach magnetized brushless AC motors

The steady-state performance of Halbach magnetized brushless ac machines when operated in constant torque and flux-weakening modes is investigated both theoretically and experimentally, with particular emphasis on the influence of cross-coupling magnetic saturation on the torque capability

Charge collective modes in an incommensurately modulated cuprate

We report the first measurement of collective charge modes of insulating Sr14Cu24O41 using inelastic resonant x-ray scattering over the complete Brillouin zone. Our results show that the intense excitation modes at the charge gap edge predominantly originate from the ladder-containing planar substructures. The observed ladder modes (E vs. Q) are found to be dispersive for momentum transfers along the "legs" but nearly localized along the "rungs". Dispersion and peakwidth characteristics are similar to the charge spectrum of 1D Mott insulators, and we show that our results can be understood in the strong coupling limit (U >> t_{ladder}> t_{chain}). The observed behavior is in marked contrast to the charge spectrum seen in most two dimensional cuprates. Quite generally, our results also show that momentum-tunability of inelastic scattering can be used to resolve mode contributions in multi-component incommensurate systems.Comment: 4+ pages, 5 figure