this article is an overview of materials used for paper sizing to improve its packaging characteristics. sizing is an important way of cellulose fibers’ modification as a mean to increase its resistance to absorption or penetration of fluids, especially water. from the functional viewpoint, this definition is equal to reinforcement through application of chemicals on paper or cardboard’s surfac...

background: composition of dust in the air due to contact with human via inhalation, ingestion and skin absorption will have a large impact on public health. in the learning environments such as universities, many people spend most of their day in contact with the dust. the purpose of this study was to evaluate the concentration of heavy metals lead, chromium and copper in the training space of...

This paper develops a one-sector endogenous growth model in which renewable natural resources are postulated as both a factor of production and as a measure of environmental quality. We show that sustained economic growth and a non-deteriorating environment can coexist along the economy’s balanced growth path. Moreover, the output growth rate is positively related to the steady-state level of n...

There are two main challenges in managing natural resources. One is to respond appropriately to the ecological characteristics of a given environment, preserving its integrity and functions while assuring a flow of benefits from it. This challenge is mostly about content— the what and when of managing natural resources. The other is to respond to the social characteristics of the same environme...

Population-environment studies have implicitly permeated demography but only until the mid-20 century has the debate been rekindled and research expanded. This article reviews the origins and history of the population-environment debate and attempts to provide insight into the most recent approaches and methodology. Beginning with the most traditional relationships established between demograph...

There is a need to select high quality forage legumes that are acid soil-tolerant, drought resistant, and persistent under the close defoliation associated with intensive pasture systems in the humid tropics. A greenhouse pot study was conducted to determine forage legume seedling growth (10 week-old) and regrowth (5 weeks after clipping to an 8-cm residual stubble) responses of ‘Amarillo’ pere...

Discusses the implications of the economic valuation of natural resources used for tourism and relates this valuation to the concept of total economic valuation. It demonstrates how applications of the concept of total economic valuation can be supportive of the conservation of natural resources used for tourism. Techniques for valuing tourism’s natural resources are then outlined and criticall...

Science, a weekly journal, is published each Friday by the American Association for the Advancement of Science at The Business Press, Incorporated, N. Queen St. and McGovern Ave., Lancaster, Pa. Founded in 1880. it has been since 1900 the official publication of the AAAS. Editorial and Advertising Offices, 1515 Massachusetts Avenue, N.W.. Washington 5, D. C. Telephone, EXecutive 60 or 6061. Cab...

This paper summarizes and extends previous research that has shown evidence of a `curse of natural resourcesa } countries with great natural resource wealth tend nevertheless to grow more slowly than resource-poor countries. This result is not easily explained by other variables, or by alternative ways to measure resource abundance. This paper shows that there is little direct evidence that omi...

Renewable natural resources include those resources useful to human economies that exhibit growth, maintenance, and recovery from exploitation over an economic planning horizon. The economics of such resources has traditionally considered stocks of fish, forests, or freshwater, much like a banker would tally interest on cash deposits. From an economic point of view, the management of biomass, s...