Bryozoan populations reflect nutrient enrichment and productivity gradients in rivers

P>1. The hypothesis that nutrient enrichment will affect bryozoan abundance was tested using two complementary investigations; a field-based method determining bryozoan abundance in 20 rivers of different nutrient concentrations by deploying statoblast (dormant propagule) traps and an experimental laboratory microcosm study measuring bryozoan growth and mortality. These two methods confirmed independently that increased nutrient concentrations in water promote increases in the biomass of freshwater bryozoans. 2. Statoblasts of the genus Plumatella were recorded in all rivers, regardless of nutrient concentrations, demonstrating that freshwater bryozoans are widespread. Concentrations of Plumatella statoblasts were high in rivers with high nutrient concentrations relative to those with low to moderate nutrient concentrations. Regression analyses indicated that phosphorus concentrations, in particular, significantly influenced statoblast concentrations. 3. Concentrations of Lophopus crystallinus statoblasts were also higher in sites characterised by high nutrient concentrations. Logistic regression analysis revealed that the presence of L. crystallinus statoblasts was significantly associated with decreasing altitude and increasing phosphorus concentrations. This apparently rare species was found in nine rivers (out of 20), seven of which were new sites for L. crystallinus. 4. Growth rates of Fredericella sultana in laboratory microcosms increased with increasing nutrient concentration and high mortality rates were associated with low nutrient concentrations. 5. Our results indicate that bryozoans respond to increasing nutrient concentrations by increased growth, resulting in higher biomasses in enriched waters. We also found that an important component of bryozoan diets can derive from food items lacking chlorophyll a. Finally, bryozoans may be used as independent proxies for inferring trophic conditions, a feature that may be especially valuable in reconstructing historical environments by assessing the abundance of statoblasts in sediment cores.

Work performance, productivity and indoor air

Temperature, relative humidity, and air quality all affect the sensory system via thermo receptors in the skin and the olfactory system. Air quality is mainly defined by the contaminants in the air. However, the most persistent memory of any space is often its odor. Strong, emotional, and past experiences are awakened by the olfactory sense. Odors can also influence cognitive processes that affect creative task performance, as well as personal memories and moods. Besides nitrogen and oxygen, the air contains particles and many chemicals that affect the efficiency of the oxygenation process in the blood, and ultimately the air breathed affects thinking and concentration. It is important to show clients the value of spending more capital on high-quality buildings that promote good ventilation. The process of achieving indoor-air quality is a continual one throughout the design, construction, commissioning, and facilities management processes. This paper reviews the evidence.

The development of convergence and accommodation

Aim: To review current literature on the development of convergence and accommodation. The accommodation and vergence systems provide the foundation upon which bifoveal binocular single vision develops. Deviations from their normal development not only are implicated in the aetiology of convergence anomalies, accommodative anomalies and strabismus, but may also be implicated in failure of the emmetropisation process. Method: This review considers the problems of researching the development of accommodation and vergence in infants and how infant research has had to differ from adult methods. It then reviews and discusses the implications of current research into the development of both systems and their linkages. Results: Vergence and accommodation develop rapidly in the first months of life, with accommodation changing from relatively fixed myopic focus in the neonatal period to adult-like responses by 4 months of age. Vergence develops gradually and becomes more accurate after 4 months of age, but has been demonstrated in infants well before the age that binocular disparity detection mechanisms are thought to develop. Hypotheses for this early vergence mechanism are discussed. The relationship between accommodation and vergence shows much more variability in infants than adult literature has found, but this apparent adult/infant difference may be partly attributed to methodological differences rather than maturational change alone. Conclusions: Variability and flexibility characterise infant responses. This variability may enable infants to develop a flexible and robust binocular system for later life. Studies of infant visual cue use may give clues to the aetiology of strabismus and refractive error.

Minimum stable convergence criteria for stochastic diffusion search

An analysis of Stochastic Diffusion Search (SDS), a novel and efficient optimisation and search algorithm, is presented, resulting in a derivation of the minimum acceptable match resulting in a stable convergence within a noisy search space. The applicability of SDS can therefore be assessed for a given problem.