Dynamics of poly(ethylene oxide) chains in water

Dynamic moduli of dilute aqueous solutions of four poly(ethylene oxide) samples were measured as a function of frequency at four temperatures. From the measurements on two quite monodisperse samples the value of the Peterlin parameter ε was determined using a shifting procedure. A definite decrease in ε was observed when going from 10°C to 40°C. Polydisperse samples were analysed by treating them as consisting of one monodisperse high-molecular mass fraction which does, and a remaining polydisperse lower-molecular mass fraction which does not contribute to the reduced dynamic moduli

Primary modules over commutative rings

The radical of a module over a commutative ring is the intersection of all prime submodules. It is proved that if R is a commutative domain which is either Noetherian or a UFD then R is one-dimensional if and only if every (finitely generated) primary R-module has prime radical, and this holds precisely when every (finitely generated) R-module satisfies the radical formula for primary submodules

Comments on the Debije-Brinkman equation

We present a macroscopic derivation of the Debije-Brinkman equation for the flow of a fluid through a polymer coil. By using an exact relation between the sedimentation coefficient and the permeability it is found that the permeability of the coil is strongly dependent on the nature of the fluid, due to local clustering of the polymer segments

Intrinsic viscosity and friction coefficient of polymer molecules in solution: Porous sphere model

The intrinsic viscosity [] and the translational friction coefficient f of polymer molecules in solution are calculated on the basis of the porous sphere model. The only information needed to predict [] and f is the polymer molecular weight, the radius of gyration in the solvent, and the permeability as a function of position in the porous sphere. For systems for which this information is available there is satisfactory agreement between predicated and directly measured values of [] and f. No adjustment of parameters is required. The influence of solvent quality is more complex than is suggested by the experimentally verified Flory-Fox relation for []; the simple form of this relation stems from the fact that two quite large effects of solvent quality approximately compensate each other. The complete flow pattern of the solvent around and through the polymer coil can be calculated. Contrary to what is usually believed the solvent flow in the polymer coil is not effectively blocked, even at the center. The connection between the present treatment and the microscopic theory of Kirkwood and Riseman is investigated

The Extent and spatial scale of connectivity among reef fish populations: implications for marine protected areas designated for fisheries enhancement

Enthusiasm for the use of no-take marine protected areas (MPAs) as management tools for the protection and enhancement of coral reef fishes is widespread. However, evidence that such marine reserves actually enhance fishery yields is limited, primarily because of difficulties in quantifying the exchange of individuals—especially larvae—between local populations within and outside the protected area. Knowledge of the extent and spatial scale of this connectivity is of vital importance for the effective design and implementation of marine reserves intended as fishery management tools. We review our current understanding of connectivity among coral reef populations, including the role of important determining factors such as pelagic larval duration, larval behavior, and hydrodynamics. We also discuss artificial and natural tagging methods that potentially can be used to track movements of larvae between marine reserves and surrounding waters. To illustrate the application of such methods, we discuss ECONAR (Ecological CONnections Among Reefs), a new, regional-scale research project designed to measure the extent of connectivity among populations of coral reef fishes in the Mesoamerican Barrier Reef System

The Effect of Entrepreneurship Education on Students’ Entrepreneurial Intentions

Purpose-The main aim of this paper is to examine the effect of entrepreneurial education on students’ entrepreneurial intentions. Also the study sought to determine whether such intention usually give rise to entrepreneurial start-up among students.Design/methodology/approach-Primary data comes from 250 students who currently have entrepreneurship as one of their courses in their institution of higher leaning within the south west of the country. Respondents filled in a detailed questionnaire on their background and other related items as regards to their entrepreneurship education. A model of regression analysis was considered most appropriate for the data analysis of the study used. The use of regression analysis results from the fact that it will enable the study to test the influence of independent variables on the dependent variable and also to ascertain the rate of change in the dependent variable as determined by increase or decrease in the independent variables.Findings-The results of the regression analysis revealed that student’s exposure to entrepreneurship education has a positive influence on the students’entrepreneurial intentions. Research Limitations/implications-Examining the impact of entrepreneurial education on students’ entrepreneurial activities tends to raise or provide some useful insights into some theoretical issues on one hand. And on the other hand, it raises some practical implications for policy makers both in the government and universities. However, this study is limited based on the information available when the research is carried out. Further research could look at the effect of the entrepreneurship education on entrepreneurial activities after graduation. This study hence recommends that the Nigeriangovernment should make entrepreneurship education a compulsory course in Nigerian schools (primary, secondary and tertiary institutions). This will help to influence youth’s attitude towards entrepreneurship. Originality /value-The study makes empirical and theoretical contribution by focussing on the research area that has received less attention especially in the context of study environmen

Duo modules

Let R be a ring. An R-module M is called a (weak) duo module provided every (direct summand) submodule of M is fully invariant. It is proved that if R is a commutative domain with field of fractions K then a torsion-free uniform R-module is a duo module if and only if every element k in K such that kM is contained in M belongs to R. Moreover every non-zero finitely generated torsion-free duo R-module is uniform. In addition, if R is a Dedekind domain then a torsion R-module is a duo module if and only if it is a weak duo module and this occurs precisely when the P-primary component of M is uniform for every maximal ideal P of R

X-ray residual stress measurements on cold-drawn steel wire

The interplanar spacing d{hkl} versus sin2 ψ distributions were measured for the 211, 310, 220 and 200 reflections from severely cold-drawn 0.7% C steel wire with a diameter of 0.25 mm. From the shape of the curves it was concluded that, as well as a 110 fibre texture and elastic anisotropy, plastic anisotropy of the ferrite crystals may be an important cause of the non-linearity in d{hkl} versus sin2 ψ. The shape of the curves, and therefore the residual state of stress of the wire, is influenced by the drawing parameters, i.e. the drawing die cone angle and the number of stages