About Notations in Multiway Array Processing

This paper gives an overview of notations used in multiway array processing. We redefine the vectorization and matricization operators to comply with some properties of the Kronecker product. The tensor product and Kronecker product are also represented with two different symbols, and it is shown how these notations lead to clearer expressions for multiway array operations. Finally, the paper recalls the useful yet widely unknown properties of the array normal law with suggested notations

Spectral Unmixing with Multiple Dictionaries

Spectral unmixing aims at recovering the spectral signatures of materials, called endmembers, mixed in a hyperspectral or multispectral image, along with their abundances. A typical assumption is that the image contains one pure pixel per endmember, in which case spectral unmixing reduces to identifying these pixels. Many fully automated methods have been proposed in recent years, but little work has been done to allow users to select areas where pure pixels are present manually or using a segmentation algorithm. Additionally, in a non-blind approach, several spectral libraries may be available rather than a single one, with a fixed number (or an upper or lower bound) of endmembers to chose from each. In this paper, we propose a multiple-dictionary constrained low-rank matrix approximation model that address these two problems. We propose an algorithm to compute this model, dubbed M2PALS, and its performance is discussed on both synthetic and real hyperspectral images

Students’ Perspectives on the First Day of Class: A Replication

Research has shown that first-day practices affect students’ motivation, grades, and end of the semester ratings of the professors. However, research on student preferences of first day practices has been conducted at public, predominantly white institutions and has not investigated if first day preferences differ at a private or historically Black university. Therefore, to investigate consistency in preferences across generations and possible differences in preferences at a private Historically Black College or University (HBCU) we assessed first day preferences and compared our results to the original study (Perlman & McCann, 1999). We sampled 230 predominantly Black students from a small private HBCU. Our findings are similar to Perlman and McCann’s results, indicating that students desire a general overview, details about grading, and getting to know the professor. Students also disliked poor use of class time and beginning course material on the first day. Analyses revealed differences in the preferences of third and fourth year students compared to first and second year students. Analyses also indicated that in our sample a smaller proportion of students cared about first day information being presented in an understandable contest, and that a higher proportion of our sample cared about setting a fun tone and disliked an uncaring or intimidating environment in contrast to Perlman & McCann’s original study

Abundances in Stars from the Red Giant Branch Tip to the Near Main Sequence in M71: II. Iron Abundance

We present [Ffe/H] abundance results that involve a sample of stars with a wide range in luminosity from luminous giants to stars near the turnoff in a globular cluster. Our sample of 25 stars in M71 includes 10 giant stars more luminous than the RHB, 3 horizontal branch stars, 9 giant stars less luminous than the RHB, and 3 stars near the turnoff. We analyzed both Fe I and Fe II lines in high dispersion spectra observed with HIRES at the W. M. Keck Observatory. We find that the [Fe/H] abundances from both Fe I and Fe II lines agree with each other and with earlier determinations. Also the [Fe/H] obtained from Fe I and Fe II lines is constant within the rather small uncertainties for this group of stars over the full range in Teff and luminosity, suggesting that NLTE effects are negligible in our iron abundance determination. In this globular cluster, there is no difference among the mean [Fe/H] of giant stars located at or above the RHB, RHB stars, giant stars located below the RHB and stars near the turnoff.Comment: Minor changes to conform to version accepted for publication, with several new figures (Paper 2 of a pair

Positive affect and its association with viral control among women with HIV infection.

We assessed the relationship between positive affect and viral suppression among women with HIV infection

A Framework to Manage the Complex Organisation of Collaborating: Its Application to Autonomous Systems

In this paper we present an analysis of the complexities of large group collaboration and its application to develop detailed requirements for collaboration schema for Autonomous Systems (AS). These requirements flow from our development of a framework for collaboration that provides a basis for designing, supporting and managing complex collaborative systems that can be applied and tested in various real world settings. We present the concepts of "collaborative flow" and "working as one" as descriptive expressions of what good collaborative teamwork can be in such scenarios. The paper considers the application of the framework within different scenarios and discuses the utility of the framework in modelling and supporting collaboration in complex organisational structures

When Do Stars Go BOOM?

The maximum mass of a star that can produce a white dwarf (WD) is an important astrophysical quantity. One of the best approaches to establishing this limit is to search for WDs in young star clusters in which only massive stars have had time to evolve and where the mass of the progenitor can be established from the cooling time of the WD together with the age of the cluster. Searches in young Milky Way clusters have not thus far yielded WD members more massive than about 1.1$~M_{\odot}$, well below the Chandrasekhar mass of $1.38~M_{\odot}$, nor progenitors with masses in excess of about $6~M_{\odot}$. However, the hunt for potentially massive WDs that escaped their cluster environs is yielding interesting candidates. To expand the cluster sample further, we used HST to survey four young and massive star clusters in the Magellanic Clouds for bright WDs that could have evolved from stars as massive as 10$~M_{\odot}$. We located five potential WD candidates in the oldest of the four clusters examined, the first extragalactic single WDs thus far discovered. As these hot WDs are very faint at optical wavelengths, final confirmation will likely have to await spectroscopy with 30-metre class telescopes.Comment: 10 pages, 5 figures, accepted to the Astrophysical Journal Letter

Spectroscopic Confirmation of Faint Lyman Break Galaxies at Redshifts Four and Five in the Hubble Ultra Deep Field

We present the faintest spectroscopically confirmed sample of redshift four and five Lyman break galaxies to date. The sample is based on slitless grism spectra of the Hubble Ultra Deep Field region from the GRAPES (Grism ACS Program for Extragalactic Science) and PEARS (Probing Evolution and Reionization Spectroscopically) projects, using the G800L grism on the HST Advanced Camera for Surveys. We report here confirmations of 39 galaxies, pre-selected as candidate Lyman break galaxies using photometric selection criteria. We compare a "traditional" V-dropout selection to a more liberal one (with V-i > 0.9), and find that the traditional criteria are about 64% complete and 81% reliable. We also study the Lyman alpha emission properties of our sample. We find that Lyman alpha emission is detected in about 1/4 of the sample, and that our broad-band color selected sample includes 55% of previously published line-selected Lyman alpha sources. Finally, we examine our stacked 2D spectra. We demonstrate that strong, spatially extended (arcsecond scale) Lyman alpha emission is not a generic property of these Lyman break galaxies, but that a modest extension of the Lyman alpha photosphere (compared to the starlight) may be present in those galaxies with prominent Lyman alpha emission.Comment: Submitted to The Astrophysical Journal. Reduced spectra from both GRAPES and PEARS are available from STScI, at http://www.stsci.edu/science/grapes/ and at http://archive.stsci.edu/prepds/pears