Differences in reproductive strategies of morphs of the genus Echinaster (Echinodermata: Asteroidea) from the Eastern Gulf of Mexico

Two morphs of the asteroid genus Echinaster, E. Type 1 and E. Type 2, have reciprocal annual cycles of reproduction and nutrient storage. The pyloric caeca (storage organs) reach maximal size over winter then decrease with increasing gametogenic activity in the spring. E. Type 1 broadcasts buoyant eggs in late May to early June. E. Type 2 deposits benthic eggs in late April. Lecithotrophic larval development is similar in both morphs except that larvae of E. Type 1 undergo a brief planktonic phase. E. Type 1 reaches sexual maturity at a larger size, expends a lower reproductive effort but has a greater absolute reproductive output than E. Type 2. E. Type 2 produces fewer, larger eggs and has a greater parental investment per egg. In both morphs, females have much higher gonadal lipid levels than males and expend a higher reproductive effort in terms organic matter and energy. Reproductive effort, reproductive output, nutrient storage in the pyloric caeca and body size varied between populations and between years in each morph. Egg size and parental investment per egg were constant. Within-morph variability is attributed to differences in nutritional state. Differences in reproductive strategy support the hypothesis that the morphs are separate species.     

MODELING MULTIPLE-USE IN NATURAL AREAS: PART 1 - THE BASIC FORMULATION1

ABSTRACT: This paper presents a mathematical model of multiple-use in natural areas. The model represents a unified system for the assessment of cases where some form of development is proposed for relatively natural areas. The focus of the model system is a benefit-cost analysis. Provisions for the full consideration of easily measured monetary costs and benefits as well as semitangible benefits accruing from environment-related activities such as outdoor recreation are contained in the model. Means for incorporating desirability as a measure of aesthetics, uniqueness, and environmental quality into the evaluation are provided. Serveral types of constraints have been imposed on the system to increase model realism. A family of compatibility constraints was designed to limit inter-use conflicts arising from incompatible activities. A form of the gradient optimization algorithm was utilized to facilitate the evaluation. The model system has application in a wide range of problems frequently encountered in environmental planning and assessment as well as natural resources management.     

Analysis of carcinogenic and mutagenic aromatic amines: An overview

The aromatic amines represent a category of considerable importance in terms of their broad industrial utilization per se as well as intermediates in the manufacture, of a wide variety of dyes which have been broadly used in textile, leather, plastic and paper products as well as in permanent and semi‐permanent coloring products. The exposure to these agents, a number of which are carcinogenic and/or mutagenic, can occur primarily via skin contact and inhalation and covers the spectrum of occupational, consumer and the general public. This overview will principally highlight a number of the recently applied methodologies (including GLC, HPLC, and SPF) for the analyses of benzidines, naphthylamines, aminobiphenyls, methylene bis(2‐chloro‐aniline); 2,4‐diaminotoluene and 2,4‐diaminoanisole with a focus on their determination in environmental and occupational samples.     

A simplified method for the design and sizing of anaerobic digestion systems for smaller farms

Anaerobic digestion (AD) as a waste treatment practice has existed for nearly 200 years and has become an accepted option for many farming and small-scale residential operations. Many developing countries now encourage the use of AD in order to meet new environmental regulations and/or to provide small amounts of energy resulting from methane generated during the process. This development has been met with some difficulty due to the lack of resources and knowledge of the systems in many of the rural communities in which these digesters are placed. A properly designed AD system can help prevent soil and water pollution as well as help mitigate methane emissions by capturing them for use as a potential energy source. This paper focuses on providing guidance to the proper design and sizing of an AD system for typical small farms, which account for the majority of dairy farms worldwide. A focus was on the implementation of such systems as they might be applied in Central America, although the aspects studied here can be applied for AD systems handling animal waste streams practically anywhere. We provide a method for sizing of anaerobic digester systems based on design standards from the US National Resource Conservation Service and using field sampled data of holding pen wash water runoff. An overview of the decision process for alternative designs is given, and simple-to-use nomographs are presented for use in sizing of an anaerobic digester system for smaller (non-industrial)-scale farms.     

Effect of Sequential Mixing and Compounding Conditions on Cellulose Acetate/Layered Silicate Nanocomposites

Injection molded nanocomposites have been successfully fabricated from cellulose acetate (CA), eco-friendly triethyl citrate (TEC) plasticizer, and organically modified clay with and without maleic anhydride grafted cellulose acetate butyrate (CAB-g-MA) as a compatibilizer. The effects of processing conditions such as mixing methods, pre-plasticizing times, extruder retention times (RT) and addition of compatibilizer on the performance of these nanocomposites have been evaluated. The cellulosic plastic with CA/TEC (80/20 wt%) was used as the polymer matrix for nanocomposite fabrication. The morphologies of these nanocomposites were evaluated through X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies. The mechanical properties of the nanocomposites were measured and have been correlated with the XRD and TEM observations. From all of the sequential mixing methods used, powder–powder mixing leads to the most transparent nanocomposites. Cellulosic plastic-based nanocomposites obtained using increased pre-plasticizing times and RT showed better exfoliated structures. In the system containing compatibilizer, the minimum retention time required for obtaining almost completely exfoliated hybrid nanocomposites was shorter than in the system without compatibilizer.