The Unusual Spectral Energy Distribution of a Galaxy Previously Reported to be at Redshift 6.68

Observations of distant galaxies are important both for understanding how galaxies form and for probing the physical conditions of the universe at the earliest epochs. It is, however, extremely difficult to identify galaxies at redshift z>5, because these galaxies are faint and exhibit few spectral features. In a previous work, we presented observations that supported the identification of a galaxy at redshift z = 6.68 in a deep STIS field. Here we present new ground-based photometry of the galaxy. We find that the galaxy exhibits moderate detections of flux in the optical B and V images that are inconsistent with the expected absence of flux at wavelength shortward of the redshifted Lyman-alpha emission line of a galaxy at redshift z>5. In addition, the new broad-band imaging data not only show flux measurements of this galaxy that are incompatible with the previous STIS measurement, but also suggest a peculiar spectral energy distribution that cannot be fit with any galaxy spectral template at any redshift. We therefore conclude that the redshift identification of this galaxy remains undetermined.Comment: 9 pages, 2 figures; To appear in Nature (30 November 2000

Approximating Weighted Duo-Preservation in Comparative Genomics

Motivated by comparative genomics, Chen et al. [9] introduced the Maximum Duo-preservation String Mapping (MDSM) problem in which we are given two strings $s_1$ and $s_2$ from the same alphabet and the goal is to find a mapping $\pi$ between them so as to maximize the number of duos preserved. A duo is any two consecutive characters in a string and it is preserved in the mapping if its two consecutive characters in $s_1$ are mapped to same two consecutive characters in $s_2$. The MDSM problem is known to be NP-hard and there are approximation algorithms for this problem [3, 5, 13], but all of them consider only the "unweighted" version of the problem in the sense that a duo from $s_1$ is preserved by mapping to any same duo in $s_2$ regardless of their positions in the respective strings. However, it is well-desired in comparative genomics to find mappings that consider preserving duos that are "closer" to each other under some distance measure [19]. In this paper, we introduce a generalized version of the problem, called the Maximum-Weight Duo-preservation String Mapping (MWDSM) problem that captures both duos-preservation and duos-distance measures in the sense that mapping a duo from $s_1$ to each preserved duo in $s_2$ has a weight, indicating the "closeness" of the two duos. The objective of the MWDSM problem is to find a mapping so as to maximize the total weight of preserved duos. In this paper, we give a polynomial-time 6-approximation algorithm for this problem.Comment: Appeared in proceedings of the 23rd International Computing and Combinatorics Conference (COCOON 2017

Mechanisms that influence the formation of high-ozone regions in the boundary layer downwind of the Asian continent in winter and spring

The seasonal variation of ozone (O3) in the boundary layer (BL) over the western Pacific is investigated using a chemistry-transport model. The model results for January and April-May 2002 were evaluated by comparison with PEACE aircraft observations. In January, strong northwesterlies efficiently transported NOx from the continent, leading to an O3 increase of approximately 5-10 ppbv over a distance of about 3000 km. In April, southwesterlies dominated due to anticyclone development over the western Pacific. Along this flow, O3 continued to be produced by NO x emitted from East Asia. This resulted in the formation of a high-O3 (> 50 ppbv) region extending along the coastal areas of East Asia. This seasonal change in O3 was driven in part by a change in the net O3 production rate due to increases in solar UV and H 2O. Its exact response depended on the NOx values in the BL. The net O3 production rate increased between winter and spring over the Asian continent and decreased over the remote western Pacific. Model simulations show that about 25% of the total O3 (of 10-20 ppbv) increase over the coastal region of Northeast Asia was due to local production from NOx emissions from China, and the rest was due to changes in background levels as well as emissions from Korea, Japan, and east Siberia. Uplift of BL air over Asia, horizontal transport in the free troposphere, and subsidence were the principal mechanisms of transporting Asian O3 to the central and eastern North Pacific Copyright 2008 by the American Geophysical Union

A note on Makeev's conjectures

A counterexample is given for the Knaster-like conjecture of Makeev for functions on $S^2$. Some particular cases of another conjecture of Makeev, on inscribing a quadrangle into a smooth simple closed curve, are solved positively

Age structure of natural versus hatchery-origin endangered Chinook salmon and implications for fisheries management in California

Maturation schedules shape the age structure of a population and influence productivity and exposure to fishing. Fish cultivated and raised in artificial environments such as hatcheries may mature at different ages compared to their natural-origin counterparts. We evaluated whether endangered Sacramento River winter-run Chinook salmon Oncorhynchus tshawytscha produced in a conservation hatchery had different maturation schedules compared to naturalorigin fish, and how any differences affected their exposure to, and impact from, the ocean salmon fishery. Using coded-wire tags collected from hatchery fish in the ocean and in-river fisheries and on the spawning grounds, and scales collected from natural-origin spawner carcasses, we reconstructed the life history of hatchery and natural-origin cohorts from 2002-2015 brood years. Hatchery fish had similar age-2 maturation rates but higher age-3 maturation rates compared to natural-origin fish, resulting in fewer age-4 individuals and an overall more truncated age structure. Because natural-origin winter-run Chinook salmon were more likely to remain at sea until age 4, they were exposed to fishing for an additional year and experienced greater reduction in escapement. Compared to natural-origin males, hatchery-origin males were much less likely to return at an older age, possibly because sexual selection that is occurring on the spawning grounds is not occurring to the same extent in the hatchery. Identifying how reproductive maturation differs across sources, sex, and life histories is critical to understanding how fisheries can disproportionately impact subsets of a population and affect its long-term population dynamics and sustainability

Possible egg masses from amphibians, gastropods, and insects in mid-Cretaceous Burmese amber

The eggs of fish, amphibians, and many invertebrates are soft, delicate structures that are only rarely preserved in the fossil record. Here we report egg masses preserved as inclusions in mid-Cretaceous amber deposits of Myanmar. Of five specimens recovered, three of the egg masses probably pertain to insects, but the other two appear different. One mass is composed of relatively stiff eggs that retain their shape throughout the mass and may be linked by mucoid strands. This morphology resembles that of some terrestrial molluscs. The second mass is composed of softer eggs that have compressed one another so that their shapes are strongly distorted within the mass. These eggs most closely resemble those of amphibians. Given the forest environment reconstructed for the amber locality, the eggs were presumably attached on or close to the resin producing tree

FEM prediction of welding residual stresses in fibre laser welded AA 2024-T3 and comparison with experimental measurement

Welding generates a considerable amount of residual stresses which affect the structural integrity of welded components. It is often assumed that the magnitude of residual stresses around the welded joint is as high as the yield stress of the material. In this investigation, such assumption was found to be overly conservative and failed to accurately represent the distribution of residual stresses in fibre laser-welded aluminium alloy 2024-T3 sheets. Welding simulation based on the finite element method was used to reliably determine the distribution and magnitude of transient residual stress fields and distortions in thin sheets welded using three different sets of welding parameters. The accuracy of the finite element models was checked by calibrating with experimentally measured weld pool geometries and temperature field prior to conducting parametric studies. X-ray and neutron diffraction measurements were performed on the surface and in the bulk of the welded components, respectively, and compared with numerical results. The influence of weld metal softening, welding parameters and restraints on residual stresses and distortion were investigated systematically by numerically simulating ideal conditions which eliminate the practical limitations of conducting experimental studies, for process optimization as well as evaluation of in-service structure integrity and failure modes of the welded sheets

Towards a design process for computer-aided biomimetics

Computer-Aided Biomimetics (CAB) tools aim to support the integration of relevant biological knowledge into biomimetic problem-solving processes. Specific steps of biomimetic processes that require support include the identification, selection and abstraction of relevant biological analogies. Existing CAB tools usually aim to support these steps by describing biological systems in terms of functions, although engineering functions do not map naturally to biological functions. Consequentially, the resulting static, functional view provides an incomplete understanding of biological processes, which are dynamic, cyclic and self-organizing. This paper proposes an alternative approach that revolves around the concept of trade-offs. The aim is to include the biological context, such as environmental characteristics, that may provide information crucial to the transfer of biological information to an engineering application. The proposed design process is exemplified by an illustrative case study