Snip20170227_6

On Minimal Rigidity of Prisms

Abstract

The Cartesian product Cm X Pn of a cycle Cm and a path Pn, n ~ 2, is called a prism. It can be checked from [2] that points in the Euclidean space R 3 can be chosen to represent the vertices of the prism such that the distance between points representing adjacent vertices is 1. Thus, Cm X Pn is a so called unit graph in R 3 . Clearly, this graph is flexible(not rigid) in R 3 . We can flex the prism so that the distance between some non-adjacent vertices will be equal to 1. Then, a new unit edge can be added to join such a pair of vertices. Read More

The Spectra of Some Asymmetric, Circulant and r-regular Digraphs and their Complements

The Spectra of Some Asymmetric, Circulant and r-regular Digraphs and their Complements

Abstract

Let G be a digraph and A( G) be its adjacency matrix. The spectrum of G, denoted by Spec G is where Ao, AI, … , Ap-l are the eigenvalues of A( G) and mo, m1, … , m – 1 are their corresponding multiplicities. This paper discusses some properties of the spectrum of four different classes of asymmetric, circulant, and r-regular digraphs and their complements. Read More

On Topologies and Reflexive Transitive Relations On Finite Sets

On Topologies and Reflexive Transitive Relations On Finite Sets

Abstract

For finite sets, the concepts of topology and reflexive transitive relations are shown to be equivalent; thus a topologv on a finite set can be represented by an incidence relation, and a function between finite topological spaces has a matrix representation. A theorem on when and only when this matrix representation is a representation for a continuous function is then given. Read More

Conceptual Understanding of Forces Among Physics Majors

Conceptual Understanding of Forces Among Physics Majors

Abstract

Conceptual understanding of forces among physics majors at De La Salle University were evaluated using the Force Concept Inventory (FCI). The FCJ scores were found to vary from an average of 23.0% for freshmen to 39.74% for seniors. Only one out of 81 physics majors of all year levels was found to be a clearly Newtonian thinker. While there is a marked difference in the understanding of inertia and falling bodies between freshmen and seniors, conceptual understanding of kinematics, Newton’s 2’d and 3’d Laws, and force identification did not reach the 50% level from first to fourth year. Read More

Acetamide as potential C- and N-source of the extremely acid and heavy metal resistant filamentous fungus, Bispora sp.

Acetamide as potential C- and N-source of the extremely acid and heavy metal resistant filamentous fungus, Bispora sp.

Abstract

The extremely acid resistant filamentous fungus Bispora sp. (possessing two distinct growth optima at pH 1 and pH 7) is able to utilize metal complexed cyanides as N-source and to grow with acetamide as the only nitrogen and carbon source at both pH 1. 0 and 7. 0, whereas little growth is observed with formam ide as N-source. The nitrogen content of the fungus grown with acetamide is similar tp ‘that of the control grown with NH4+ as N-source but higher than those cultures deprived of nitrogen. In the absence of appropriate substrates the fungus did not express amidases such, as urease, formamidase, acetamidase, whereas in the presence of formam ide and acetamide, formamidase activity, but no acetamidase activity was observed. Read More

Air Borne Lead Contamination of Trees in Metro Manila

Air Borne Lead Contamination of Trees in Metro Manila-A Study of Environmental Hazards Related to Leaded Fuels

Abstract

The environmental hazards originating from the use of leaded fuel in Metro Manila were analyzed indirectly by investigating the Ph content and contamination of leaves of trees exposed to heavy traffic along Taft Avenue in comparison with three sites with less or no traffic in the countryside. Both the internal Pb content and the external Pb load of plants were measured. Internal Pb content of samples along Taft Avenue and the countrvside yielded an average of 6.5 mg and 0.6 mg Ph per kg dry weight respectively while that of external Pb load were 18.9 mg and 2. 74 mg Pb per kg dry weight respectively. Read More