Effect of mean on variance function estimation in nonparametric regression

Variance function estimation in nonparametric regression is considered and the minimax rate of convergence is derived. We are particularly interested in the effect of the unknown mean on the estimation of the variance function. Our results indicate that, contrary to the common practice, it is not desirable to base the estimator of the variance function on the residuals from an optimal estimator of the mean when the mean function is not smooth. Instead it is more desirable to use estimators of the mean with minimal bias. On the other hand, when the mean function is very smooth, our numerical results show that the residual-based method performs better, but not substantial better than the first-order-difference-based estimator. In addition our asymptotic results also correct the optimal rate claimed in Hall and Carroll [J. Roy. Statist. Soc. Ser. B 51 (1989) 3--14].Comment: Published in at http://dx.doi.org/10.1214/009053607000000901 the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

The first-order effect of Holocene Northern Peatlands on global carbon cycle dynamics

Given the fact that the estimated present-day carbon storage of Northern Peatlands (NP) is about 300–500 petagram (PgC, 1 petagram = 1015 gram), and the NP has been subject to a slow but persistent growth over the Holocene epoch, it is desirable to include the NP in studies of Holocene carbon cycle dynamics. Here we use an Earth system Model of Intermediate Complexity to study the first-order effect of NP on global carbon cycle dynamics in the Holocene. We prescribe the reconstructed NP growth based on data obtained from numerous sites (located in Western Siberia, North America, and Finland) where peat accumulation records have been developed. Using an inverse method, we demonstrate that the long-term debates over potential source and/or sink of terrestrial ecosystem in the Holocene are clarified by using an inverse method, and our results suggest that the primary carbon source for the changes (sinks) of atmospheric and terrestrial carbon is the ocean, presumably, due to the deep ocean sedimentation pump (the so-called alkalinity pump). Our paper here complements ref. 1 by sensitivity tests using modified boundary conditions

Spin-Injection Spectroscopy of a Spin-Orbit Coupled Fermi Gas

The coupling of the spin of electrons to their motional state lies at the heart of recently discovered topological phases of matter. Here we create and detect spin-orbit coupling in an atomic Fermi gas, a highly controllable form of quantum degenerate matter. We reveal the spin-orbit gap via spin-injection spectroscopy, which characterizes the energy-momentum dispersion and spin composition of the quantum states. For energies within the spin-orbit gap, the system acts as a spin diode. To fully inhibit transport, we open an additional spin gap, thereby creating a spin-orbit coupled lattice whose spinful band structure we probe. In the presence of s-wave interactions, such systems should display induced p-wave pairing, topological superfluidity, and Majorana edge states

Differences Between The Optical/Uv Spectra Of X-Ray Bright And X-Ray Faint QSOs

We contrast measurements of composite optical and ultraviolet (UV) spectra constructed from samples of QSOs defined by their soft X-ray brightness. X-ray bright (XB) composites show stronger emission lines in general, but particularly from the narrow line region. The difference in the [OIII]/Hbeta ratio is particularly striking, and even more so when blended FeII emission is properly subtracted. The correlation of this ratio with X-ray brightness were principal components of QSO spectral diversity found by Boroson & Green (1992). We find here that other, much weaker narrow optical forbidden lines ([OII] and NeV) are enhanced by factors of 2 to 3 in our XB composites, and that narrow line emission is also strongly enhanced in the XB UV composite. Broad permitted line fluxes are slightly larger for all XB spectra, but the narrow/broad line ratio stays similar or increases strongly with X-ray brightness for all strong permitted lines except Hbeta. Spectral differences between samples divided by their relative X-ray brightness (as measured by alpha_{ox}) exceed those seen between complementary samples divided by luminosity or radio loudness. We propose that the Baldwin effect may be a secondary correlation to the primary relationship between alpha_{ox} and emission line equivalent width. We conclude that either 1) equivalent width depends strongly on the SHAPE of the ionizing continuum, as crudely characterized here by alpha_{ox} or 2) both equivalent width and alpha_{ox} are related to some third parameter characterizing the QSO physics. One such possibility is intrinsic warm absorption; a soft X-ray absorber situated between the broad and narrow line regions can successfully account for many of the properties observed.Comment: 16 pages including 3 figures, AAS latex, plus 4 tables totaling 5 pages, to appear in ApJ Vol. 498, May 1, 199

Chinese adzuki bean germplasm: 1. Evaluation of agronomic traits

A core collection of adzuki beans, representing the germplasm of Chinese land races, was screened at Warwick Australia in a replicated yield trial sown mid-summer. Grain yield, yield components, phenologic traits, vegetative characteristics, and morphologic descriptors were recorded for all accessions plus Japanese-derived check varieties. Accessions from southern China were later flowering, had smaller seed, and grew taller than those from central China. Grain yield was greatest for accessions from central China, whereas both north Chinese and Japanese check accessions were generally low yielding. The evaluation of diversity displayed trends associated with latitude of germplasm origin, which were positive or negative according to the trait. Similarly, the germplasm diversity in duration of crop growth phases and in rate of yield expression was also associated with latitude of landrace origin. Localised variations from these trends were found for seed size and for number of pods per plant. Various trends with latitude of origin were found for natural incidence of powdery mildew, for growth habit, plant height, vining and leaf colour. However, traits not associated with latitude of germplasm origin included primary and secondary seed colour, mature pod colour, and degree of branching. The evaluation suggests that selections from this greater range of genetic diversity may allow higher yielding varieties than the current Japanese-derived standards to be developed for Australia

Sex Hormone-Binding Globulin Levels Are Inversely Associated With Nonalcoholic Fatty Liver Disease in HIV-Infected and -Uninfected Men.

BackgroundNonalcoholic fatty liver disease (NAFLD) is a leading cause of liver disease worldwide. Elevated sex hormone-binding globulin (SHBG) levels have been observed in the setting of HIV and may protect against some metabolic disorders. We aimed to investigate whether higher SHBG levels may protect against NAFLD in men with/without HIV.MethodsNAFLD was assessed using noncontrast computed tomography in 530 men in the Multicenter AIDS Cohort Study (MACS) who drank <3 alcoholic drinks/d and were uninfected with chronic hepatitis C or B (340HIV+, 190HIV-). Morning serum samples were tested for SHBG, total testosterone (TT), and adiponectin. Multivariable logistic regression was used to assess associations between HIV, SHBG, TT, adiponectin, and NAFLD.ResultsMedian SHBG was highest among HIV+/NAFLD- men and lowest among HIV-/NAFLD+ men. Adjusted for demographics, HIV, visceral adiposity, HOMA-IR, TT, and PNPLA3 genotype, higher SHBG was associated with lower odds of NAFLD (odds ratio [OR], 0.52 per doubling; 95% confidence interval [CI], 0.34-0.80). In separate multivariable models without SHBG, HIV (OR, 0.46; 95% CI, 0.26-0.79) and higher adiponectin (OR, 0.66 per doubling; 95% CI, 0.49-0.89) were associated with lower NAFLD odds, whereas TT was not significantly associated (OR, 0.74 per doubling; 95% CI, 0.53-1.04). Adjusting for SHBG attenuated the associations of HIV (OR, 0.61; 95% CI, 0.34-1.08) and adiponectin (OR, 0.74; 95% CI, 0.54-1.02) with NAFLD.ConclusionsSHBG levels were higher among HIV+ men, were independently associated with lower NAFLD, and could partially explain the associations of HIV and higher adiponectin with lower NAFLD in our cohort. These findings suggest that SHBG may protect against NAFLD, supporting further prospective and mechanistic studies

Accessibility-based reranking in multimedia search engines

Traditional multimedia search engines retrieve results based mostly on the query submitted by the user, or using a log of previous searches to provide personalized results, while not considering the accessibility of the results for users with vision or other types of impairments. In this paper, a novel approach is presented which incorporates the accessibility of images for users with various vision impairments, such as color blindness, cataract and glaucoma, in order to rerank the results of an image search engine. The accessibility of individual images is measured through the use of vision simulation filters. Multi-objective optimization techniques utilizing the image accessibility scores are used to handle users with multiple vision impairments, while the impairment profile of a specific user is used to select one from the Pareto-optimal solutions. The proposed approach has been tested with two image datasets, using both simulated and real impaired users, and the results verify its applicability. Although the proposed method has been used for vision accessibility-based reranking, it can also be extended for other types of personalization context

Slicing the Torus: Obscuring Structures in Quasars

Quasars and Active Galactic Nuclei (AGNs) are often obscured by dust and gas. It is normally assumed that the obscuration occurs in an oblate "obscuring torus", that begins at the radius at which the most refractive dust can remain solid. The most famous form of this torus is a donut-shaped region of molecular gas with a large scale-height. While this model is elegant and accounts for many phenomena at once, it does not hold up to detailed tests. Instead the obscuration in AGNs must occur on a wide range of scales and be due to a minimum of three physically distinct absorbers. Slicing the "torus" into these three regions will allow interesting physics of the AGN to be extracted.Comment: 8 pages, 1 figure. To appear in the proceedings of the conference "The central kiloparsec in Galactic Nuclei:Astronomy at High Angular Resolution 2011", open access Journal of Physics: Conference Series (JPCS), published by IOP Publishin

Ultraviolet and optical properties of Narrow-Line Seyfert 1 galaxies

Narrow Line Seyfert 1 (NLS1) galaxies are remarkable for their extreme continuum and emission line properties which are not well understood. New results bearing on the spectroscopic characteristics of these objects are presented here, with the aim of establishing their typical ultraviolet and optical spectral behavior. We employ HST observations of 22 NLS1s, which represent a substantial improvement over previous work in terms of data quality and sample size. High signal-to-noise NLS1 composite spectra are constructed, allowing accurate measurements of the continuum shape and the strengths, ratios, and widths for lines, including weak features which are barely identifiable in other Active Galactic Nuclei (AGN) composites. We find that the NLS1 sources have redder UV-blue continua than those typically measured in other quasars and Seyferts. Objects with UV line absorption show redder spectra, suggesting that dust is important in modifying the continuum shapes. The data also permit a detailed investigation of the previously proposed link between NLS1s and z >~ 4 quasars. Direct comparison of their composite spectra, as well as a Principal Component Analysis, suggest that high-z QSOs do not show a strong preference toward NLS1 behavior.Comment: 23 pages (incl. 9 figures, 4 tables), to appear in The Publications of the Astronomical Society of the Pacifi

Data-driven image color theme enhancement

Proceedings of the 3rd ACM SIGGRAPH Asia 2010, Seoul, South Korea, 15-18 December 2010It is often important for designers and photographers to convey or enhance desired color themes in their work. A color theme is typically defined as a template of colors and an associated verbal description. This paper presents a data-driven method for enhancing a desired color theme in an image. We formulate our goal as a unified optimization that simultaneously considers a desired color theme, texture-color relationships as well as automatic or user-specified color constraints. Quantifying the difference between an image and a color theme is made possible by color mood spaces and a generalization of an additivity relationship for two-color combinations. We incorporate prior knowledge, such as texture-color relationships, extracted from a database of photographs to maintain a natural look of the edited images. Experiments and a user study have confirmed the effectiveness of our method. © 2010 ACM.postprin