Nonlinear distortions and multisine signals. I. Measuring the bestlinear approximation

This paper examines the effects of nonlinearities on frequency response function measurements using periodic multifrequency signals. A class of broadband pilot test signals is proposed, termed sparse odd multisines, which can be used to establish the system bandwidth and detect nonlinearities. Signals are then defined within this class which allow the measurement of the best linear approximation of a nonlinear system. A comparison is made with related work in this area     

Delivering Best Value in Highways Major Maintenance Schemes: Case Study

The Construction Management Framework (CMF) is a contract established by the Highways Agency in the United Kingdom, where collaborative working is used within a framework setting to deliver the best value in highways major renewals and improvements schemes. This research aims to establish the effectiveness of the CMF in achieving this aim. It aims to define best value as it is understood collectively by the participants in the framework, and evaluate the performance measurement used in terms of its relevance and suitability to deliver the best value. The research also looks at perceptions of the performance of the CMF by those companies included in the framework, and the benefits and disadvantages of using this type of arrangement in highway work. Data collected from the client were compared to that given by the contractors, supply chain, and construction managers of the CMF; results showed a perception by those involved in the framework that construction management is suited to the type of work it is currently used for, and there is potential for similar CMFs to be used elsewhere in the construction industry. However, the research also found that there is a need to improve the performance measures so that value is properly reflected in the goals of the CMF; and the presentation of evidence that demonstrates the benefits that can be gained using this procurement route.     

Changing, priming, and acting on values: Effects via motivational relations in a circular model.

Circular models of values and goals suggest that some motivational aims are consistent with each other, some oppose each other, and others are orthogonal to each other. The present experiments tested this idea explicitly by examining how value confrontation and priming methods influence values and value-consistent behaviors throughout the entire value system. Experiment 1 revealed that change in 1 set of social values causes motivationally compatible values to increase in importance, whereas motivationally incompatible values decrease in importance and orthogonal values remain the same. Experiment 2 found that priming security values reduced the better-than-average effect, but priming stimulation values increased it. Similarly, Experiments 3 and 4 found that priming security values increased cleanliness and decreased curiosity behaviors, whereas priming self-direction values decreased cleanliness and increased curiosity behaviors. Experiment 5 found that priming achievement values increased success at puzzle completion and decreased helpfulness to an experimenter, whereas priming with benevolence values decreased success and increased helpfulness. These results highlight the importance of circular models describing motivational interconnections between values and personal goals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reply to comments on "Derivation of numerical values for the World Health Organization guidelines for recreational waters"

The contribution addressed reveals an optimistic design philosophy likely to systematically underestimate risk in epidemiologic studies into the health effects of bathing water exposures. The authors seem to recommend that data on the 'exposure' measure (i.e. water quality) in such studies should be acquired in a similar manner to that used for regulatory sampling. This approach may compromise the quality of the epidemiologic investigations undertaken. It may result in imprecise estimates of exposure because it ignores the fact that regulatory timescales and spatial resolution (even if artificially compressed to a bathing day) can mask large spatial and temporal variability in water quality. If this variability is ignored by taking some mean value and attributing that to all of those exposed in a period at a study location, many bathers may be misclassified and the studies may be biased to a 'no-effect' conclusion. A more appropriate approach is to maximise the precision of the epidemiologic investigations by measurement of individual exposure (or water quality) at the place and time of the exposure, as has been done in randomised volunteer studies in the UK and Germany. The precise epidemiologic relationships linking 'exposure' with 'illness' can then be related to the probability of exposure to particular water quality by a 'normal bather' using the known probability distribution of the exposure variable (i.e. faecal indicator concentration) in the regulated bathing waters. We suggest that any research protocol where poor sampling design for water quality assessment is justified because regulatory monitoring is equally imprecise may be fundamentally flawed. The rationale for this assessment is that the epidemiology is the starting point and evidence-base for 'standards'. If precision is not maximised at this stage in the process it compromises the credibility of the standards design process. The negative effects of the approach advocated in this 'comment' are illustrated using published research findings used to derive the figures illustrated in Wymer et al. [2005. Comment on derivation of numerical values for the World Health Organization guidelines for recreational waters. Water Research 39, 2774-2777].     

Avalanche multiplication characteristics ofAl0.8Ga0.2As diodes

The avalanche multiplication characteristics of Al_0.8Ga _0.2As have been investigated in a series of p-i-n and n-i-p diodes with i-region widths, w, varying from 1 μm to 0.025 μm. The electron ionization coefficient, α, is found to be consistently higher than the hole ionization coefficient, β, over the entire range of electric fields investigated. By contrast with Al_xGa _1-xAs (x⩽0.6) a significant difference between the electron and hole initiated multiplication characteristics of very thin Al_0.8Ga_0.2As diodes (w=0.025 μm) was observed. Dead space effects in the diodes with w⩽0.1 μm were found to reduce the multiplication at low bias below the values predicted from bulk ionization coefficients. Effective α and β that are independent of w have been deduced from measurements and are able to reproduce accurately the multiplication characteristics of diodes with w⩾0.1 μm and breakdown voltages of all diodes with good accuracy. By performing a simple correction for the dead space, the multiplication characteristics of even thinner diodes were also predicted with reasonable accuracy     

Production and composition of milk from Jersey cows administered bovine somatotropin and fed ruminally protected amino acids

Eight multiparous and 4 primiparous Jersey cows averaging 92 d of lactation were utilized in a replicated 4 x 4 Latin square design with 28-d periods to determine responses to bovine somatotropin (bST) and ruminally protected Met and Lys when diets were fed that contained supplemental fat. Treatments were 1) control [no bST or ruminally protected amino acids (AA)], 2) control plus bST, 3) control plus ruminally protected AA, and 4) control plus bST plus ruminally protected AA. Dry matter intake was increased by bST but was unaffected by ruminally protected AA. Milk yield was increased by bST but was not altered by ruminally protected AA compared with the control diet. The bST tended to increase percentages of fat and total solids in milk and increased yields of fat, protein, 3.5% fat-corrected milk, and total solids. Ruminally protected AA increased percentages of fat, protein, and total solids in milk; however, yields of milk components were unaffected by ruminally protected AA. Body weight and body condition scores were unaffected by treatment. Concentrations of essential AA in plasma were unaffected by bST administration. Ruminally protected Met and Lys increased the concentration of Met and tended to increase the concentration of Lys in plasma. The lack of an increase in yields of milk and milk protein when ruminally protected AA were fed suggests that adequate amounts of Met and Lys were supplied by the control diet and protein reserves of the cows to meet the AA requirements for synthesis of milk and milk components.     

Thyroid cancer after exposure to external radiation: a pooled analysis of seven studies

The thyroid gland of children is especially vulnerable to the carcinogenic action of ionizing radiation. To provide insights into various modifying influences on risk, seven major studies with organ doses to individual subjects were evaluated. Five cohort studies (atomic bomb survivors, children treated for tinea capitis, two studies of children irradiated for enlarged tonsils, and infants irradiated for an enlarged thymus gland) and two case-control studies (patients with cervical cancer and childhood cancer) were studied. The combined studies include almost 120,000 people (approximately 58,000 exposed to a wide range of doses and 61,000 nonexposed subjects), nearly 700 thyroid cancers and 3,000,000 person years of follow-up. For persons exposed to radiation before age 15 years, linearity best described the dose response, even down to 0.10 Gy. At the highest doses (> 10 Gy), associated with cancer therapy, there appeared to be a decrease or leveling of risk. For childhood exposures, the pooled excess relative risk per Gy (ERR/Gy) was 7.7 (95% CI = 2.1, 28.7) and the excess absolute risk per 10(4) PY Gy (EAR/10(4) PY Gy) was 4.4 (95% CI = 1.9, 10.1). The attributable risk percent (AR%) at 1 Gy was 88%. However, these summary estimates were affected strongly by age at exposure even within this limited age range. The ERR was greater (P = 0.07) for females than males, but the findings from the individual studies were not consistent. The EAR was higher among women, reflecting their higher rate of naturally occurring thyroid cancer. The distribution of ERR over time followed neither a simple multiplicative nor an additive pattern in relation to background occurrence. Only two cases were seen within 5 years of exposure. The ERR began to decline about 30 years after exposure but was still elevated at 40 years. Risk also decreased significantly with increasing age at exposure, with little risk apparent after age 20 years. Based on limited data, there was a suggestion that spreading dose over time (from a few days to > 1 year) may lower risk, possibly due to the opportunity for cellular repair mechanisms to operate. The thyroid gland in children has one of the highest risk coefficients of any organ and is the only tissue with convincing evidence for risk about 1.10 Gy.     

Sublethal concentrations of mercury in river otters: monitoring environmental contamination

Hair, muscle, and liver mercury concentrations were determined in river otter (Lutra canadensis) carcasses collected from the lower coastal plain and piedmont of Georgia. Mean muscle and hair mercury concentrations were greater (P < 0.001) in otters from the lower coastal plain (4.42 and 24.25 mg/kg wet wt, respectively) compared to otters from the piedmont (1.48 and 15.24 mg/kg, respectively). Liver tissue from lower coastal plain otters averaged 7.53 mg/kg mercury. Mean fetus brain and muscle mercury concentrations were 1.03 and 1.58 mg/kg wet wt, respectively, and fetal muscle mercury concentrations were correlated (r = 0.92) with maternal muscle mercury concentrations. Comparison of mercury concentrations found in Georgia otters to those associated with adverse effects in otter and mink (Mustela vison), indicate sublethal contamination with concentrations in some individuals approaching that observed in experimentally dosed individuals that developed clinical signs of mercurialism. Mercury concentrations in fish from the lower coastal plain approached or exceeded concentrations demonstrated to be toxic to experimentally dosed otters.     

Fate of 15N-labelled urea when applied to long-term fertilized soils of varying fertility

Nutrient Cycling in Agroecosystems - Quantifying the fate of nitrogen (N) fertilizer is essential to develop more sustainable agricultural N management practices. However, our understanding of N...     

Meeting the Challenge of Chemical Language Barriers in University Level Chemistry Education

The specific yet varied challenges chemical language presents to students learning the subject are widely recognised. However, to effectively engage a student population becoming increasingly diverse in terms of culture, language and prior knowledge chemistry educators must develop pedagogical strategies that address issues of language comprehension. In this paper we discuss the body of literature that provides evidence of the multiple challenges that the language of chemistry presents students. These include: words in a scientific context, words with dual meaning, similar words and symbolic language. The chemistry learning triplet is used to illustrate how students must use chemical language to move between the macroscopic, sub‐microscopic and symbolic levels. Combining evidence from our research and the wider literature we describe a novel model of linguistic demand in multiple dimensions that represents the challenge of chemical language. This model can be used to assess the linguistic demand of teaching resources and to focus the appropriate use of language and literacy informed pedagogical strategies.