Acquired immunity against Cooperia spp. and Ostertagia spp. in calves: effect of level of exposure and timing of the midsummer increase

In two experiments, groups of calves were exposed to different levels and patterns of infection with Ostertagia spp. and Cooperia spp. The experimental design simulated the stereotypic pattern of herbage infestation, including both as normal and a delayed midsummer increase, under conditions of set-stocking. After this simulated 'first grazing season', calves were followed during the subsequent winter housing. At the end of that housing period some calves were challenged with 100,000 L3 Cooperia spp. and 40,000 L3 Ostertagia spp. and slaughtered 23 days later. All previously infected calves were protected against the establishment of the challenge infection with Cooperia spp., but not against Ostertagia spp. For the latter a significant negative correlation was found between worm count and previous level of exposure to infection. During the simulated first grazing season, changes in the ratio of Cooperia to Ostertagia eggs in the faecal egg output and the genus-specific egg count were influenced by both the level of exposure and the timing of the midsummer increase. It is concluded that acquired immunity against both parasite genera develops depending on the level of exposure to infection during a first grazing season, and that delaying the midsummer increase results in a delay of the acquisition of an effective immunity as measured by faecal egg counts and the ratio of Cooperia to Ostertagia egg output.     

Stress-induced muscle effort as a cause of repetitive strain injury?

The influence of stress-induced muscle effort during computer utilization was tested in patients with repetitive strain injury (RSI). Twenty academic researchers with a formal medical diagnosis of RSI and 20 matched controls, randomly selected from a sample of 71 colleagues with and without RSI, typed after stress (induced via an intelligence/skill task under social pressure) and after relaxation. Results indicated that both groups had more electromyography (EMG) activity in the shoulder muscles during typing after stress than after relaxation, but that patients started with higher baseline muscle activity. Furthermore, EMG activity of different muscle groups during typing after stress correlated among controls, but not among patients. Finally, analysis of intake forms showed that patients scored higher than controls on neuroticism and alexithymia, but not on extraversion, openness, agreeableness and conscientiousness. It was concluded that deviations in muscle activity during computer utilization, as well as neuroticism and alexithymia, may be risk factors for RSI.     

Topography following keratoplasty in cats is not representative of that in humans

The excurrent duct system of the rat submandibular gland consists of a number of distinct segments. Using the direction of salivary flow as a reference point, these segments are, in order, intercalated duct, granular convoluted tubule, striated duct, excretory duct, main excretory duct (MED), and salivary bladder (which is an expanded portion of the MED). Because these ducts (with the exception of the MED and the salivary bladder) are encased in secretory endpieces, they are difficult to locate and to observe by scanning electron microscopy. A simple method has been devised to rid the gland of these obscuring endpieces so that the detailed architecture of the duct system can be examined. Rat submandibular glands were fixed initially by vascular perfusion with half-strength Karnovsky's fixative. The connective tissue capsule was removed from extirpated glands and the glands remained in fixative for varying lengths of time. For our purposes, a 30-minute immersion in the aldehyde mixture was optimum. After the sublingual gland was removed, the submandibular gland was softly struck with forceps having rounded tips, then shaken in fixative or buffer. The tissue that remained was postfixed in osmium tetroxide. This method results in the complete divestment of nonductular parenchyma from the rat submandibular gland, leaving the duct system clean and ready for microscopic examination.     

Recognising the potential for renewable energy heating and cooling

Heating and cooling in the industrial, commercial, and domestic sectors constitute around 40–50% of total global final energy demand. A wide range of renewable energy heating and cooling (REHC) technologies exists but they are presently only used to meet around 2–3% of total world demand (excluding from traditional biomass). Several of these technologies are mature, their markets are growing, and their costs relative to conventional heating and cooling systems continue to decline. However, in most countries, policies developed to encourage the wider deployment of renewable electricity generation, transport biofuels and energy efficiency have over-shadowed policies aimed at REHC technology deployment. This paper, based on the findings of the International Energy Agency publication Renewables for Heating and Cooling—Untapped Potential, outlines the present and future markets and compares the costs of providing heating and cooling services from solar, geothermal and biomass resources. It analyses current policies and experiences and makes recommendations to support enhanced market deployment of REHC technologies to provide greater energy supply security and climate change mitigation. If policies as successfully implemented by the leading countries were to be replicated elsewhere (possibly after modification to better suit local conditions), there would be good potential to significantly increase the share of renewable energy in providing heating and cooling services.     

Adverse Weather and Commuting Speed

This paper investigates the welfare effect of travelling through congested areas and adverse weather through changes in the speed of individuals’ car trips based on the entire commuting trip. Weather measurements are local and time specific (hourly basis). As most commuters travel twice a day between home and work, we are able to employ panel data techniques, which deals with issues related to unobserved heterogeneity and data selection. We find that travelling through congested areas reduces speed by about 7%. For most commuters the welfare effects of adverse weather conditions are negative but small. However, the commuters’ welfare costs due to rain are rather substantial during the evening peak in congested areas (and up to 12% of the overall commuting costs).     

On the distance dependence of the price elasticity of telecommunications demand; review, analysis, and alternative theoretical backgrounds

The positive correlation between the absolute price elasticity of telecommunications demand and the distance of the calling relation is often suggested and presented as an empirical regularity. In this paper we first present an overview of existing studies to buttress the distance dependence empirically. A statistical analysis of the results confirms the existence of distance dependence, and gives insight into the size of the effect: doubling the distance leads to an increase of the elasticity of 0.07.  Next we look for various explanations of the distance dependence. We analyze the roles of the functional form of demand functions in conjunction with the dependence of price on distance, and consider whether spatial interaction theory can provide an explanation. One of the interesting findings is that the price effect may explain the distance dependence, but that this explanation is not unequivocal. In addition we show that incorporating spatial interaction theory elements in a quite basic utility maximization model of information demand also leads to distance dependent telecommunications demand. Received: December 1999/Accepted: July 2001     

The capacity of children with and without asthma to detect external resistive loads on breathing

Clinical observations and research with adults consistently showed that subjective symptoms of asthma poorly reflect actual airway obstruction. The lack of accurate symptom perception poses a problem for medication and management of asthma. The accuracy of airflow detection was studied in 46 children with and 46 without asthma (aged 7-18 years). They breathed through a facemask and responded to load stimuli of different intensity. Sessions consisted of 10 blocks of 5 min, each with 10 stimuli presented. Experiment 1: Loads of increasing intensity presented to 36 children with and 36 without asthma. Seven asthmatics had a reliable detection threshold (just noticeable difference, jnd) analogous to approximately equal to 64% fall in forced expiratory volume in 1 sec (FEV1). Ten normal controls had a jnd of approximately 39% fall. Experiment 2: Loads randomly presented to 10 children with and 10 without asthma. Four asthmatics had a jnd of approximately equal to 64% fall in FEV1. Six normal controls had a jnd of approximately equal to 39% fall. The results demonstrated that children generally were poorly perceiving load stimuli and that asthmatics were less accurate.     

Water recovery from sewage using forward osmosis

This research is part of the Sewer Mining project aimed at developing a new technological concept by extracting water from sewage by means of forward osmosis (FO). FO, in combination with a reconcentration system, e.g. reverse osmosis (RO) is used to recover high-quality water. Furthermore, the subsequent concentrated sewage (containing an inherent energy content) can be converted into a renewable energy (RE) source (i.e. biogas). The effectiveness of FO membranes in the recovery of water from sewage has been evaluated. Stable FO water flux values (>4.3 LMH) were obtained with primary effluent (screened, not treated) used as the feed solution. Fouling of the membrane was also induced and further investigated. Accumulated fouling was found to be apparent, but not irreversible. Sewer Mining could lead to a more economical and sustainable treatment of wastewater, facilitating the extraction of water and energy from sewage and changing the way it is perceived: not as waste, but as a resource.     

Possibilities for reuse of treated domestic wastewater in the Netherlands

The implementation of wastewater reuse is becoming an increasingly important means of supplementing water supply needs and/or reducing costs. The present paper provides examples of possible uses of treated domestic effluent for the three sectors, i.e. public water supply, industrial and agricultural uses with the aim to address the feasibility of these applications. It is concluded that, although The Netherlands as a whole is considered to be a low water stressed country, regional fresh water scarcity and costs can result in the need for applications of domestic wastewater reuse.