The strong Lefschetz property in codimension two

Every artinian quotient of $K[x,y]$ has the strong Lefschetz property if $K$ is a field of characteristic zero or is an infinite field whose characteristic is greater than the regularity of the quotient. We improve this bound in the case of monomial ideals. Using this we classify when both bounds are sharp. Moreover, we prove that the artinian quotient of a monomial ideal in $K[x,y]$ always has the strong Lefschetz property, regardless of the characteristic of the field, exactly when the ideal is lexsegment. As a consequence we describe a family of non-monomial complete intersections that always have the strong Lefschetz property.Comment: 18 pages, 1 figure; v2: Updated history and reference

North American Species of the Genus Hydrochoreutes (Acarina: Pionidae)

Excerpt: Members of the water mite genus Hydrochoreutes have a Holarctic distribution. They are found in lakes, ponds, and sluggish streams, but usually only in small numbers and therefore long series of specimens are difficult to obtain. Two species, ungulatus (Koch) and krameri Piersig, have a widespread range in Europe and Siberia and the latter species is also known from Algeria. Marshall (1937) reported ungulatus from Maine, Michigan, Wisconsin and California. However, the present author has seen no specimens from North America which can be assigned to the latter species and the illustrations in Marshall\u27s paper are definitely not those of ungulatus. Therefore. there are no authentic records of the latter species in the New World. Cook (1956) named a new species, intermedius, from North America. Both the description and illustrations are inadequate for the latter and it is treated along with four new species in this paper

Nauty in Macaulay2

We introduce a new Macaulay2 package, Nauty, which gives access to powerful methods on graphs provided by the software nauty by Brendan McKay. The primary motivation for accessing nauty is to determine if two graphs are isomorphic. We also implement methods to generate families of graphs restricted in various ways using tools provided with the software nauty.Comment: 4 pages; second updated for clarit

Explaining patterns in the ratification of global environmental treaties

A study was made of the ratification behavior of 160 countries with respect to 38 global environmental treaties. The study identifies and explains patterns in the ratification of treaties, providing two means of assessing the likelihood that any given country will support global environmental treaties. National ratification totals reveal a pattern of high ratification by countries in Western Europe, North America, Japan, Australia, and New Zealand. A country's standing within the range of high to low ratification rates can be explained by the statistical model developed in the study. This research allows one to identify countries likely to support global environmental treaties

“Stickiness”: Gauging students’ attention to online learning activities

Purpose: Online content developers use the term “stickiness” to refer to the ability of their online service or game to attract and hold the attention of users and create a compelling and magnetic reason for them to return repeatedly (examples include virtual pets and social media). In business circles, the same term connotes the level of consumer loyalty to a particular brand. This paper aims to extend the concept of “stickiness” not only to describe repeat return and commitment to the learning “product”, but also as a measure of the extent to which students are engaged in online learning opportunities. Design/methodology/approach: This paper explores the efficacy of several approaches to the monitoring and measuring of online learning environments, and proposes a framework for assessing the extent to which these environments are compelling, engaging and “sticky”. Findings: In particular, the exploration so far has highlighted the difference between how lecturers have monitored the engagement of students in a face-to-face setting versus the online teaching environment. Practical implications: In the higher education environment where increasingly students are being asked to access learning in the online space, it is vital for teachers to be in a position to monitor and guide students in their engagement with online materials. Originality/value: The mere presence of learning materials online is not sufficient evidence of engagement. This paper offers options for testing specific attention to online materials allowing greater assurance around engagement with relevant and effective online learning activities

Multiple Myeloma : an update on disease biology and therapy

Multiple myeloma is a malignancy of immunoglobulin producing plasma cells. Clinical features include bone pain due to lytic bone lesions or pathological fractures, anemia, symptomatic hypercalcemia, renal insufficiency, recurrent infections and amyloidosis. In the last few years, there have been considerable advances in the understanding of the biology of this disease. While multiple myeloma is biologically diverse, several oncogenes are activated in this illness. In addition, the role of the bone marrow microenvironment to support the growth and survival of the malignant cells has been well described. In this review, we discuss recent developments in the molecular pathogenesis of myeloma. These recent observations are being translated into novel therapeutic approaches that target both the tumor cell as well as the stroma. Current therapeutic strategies are discussed.peer-reviewe