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Arithmetic Differences (arithmetic + difference)

Distribution by Scientific Domains

Medical Sciences	50%

Selected Abstracts

Cognitive Arithmetic Differences in Learning Difficulty Groups and the Role of Behavioral Inattention

LEARNING DISABILITIES RESEARCH & PRACTICE, Issue 1 2007
Paul T. Cirino
The objectives of this study were to (1) evaluate group differences in specific arithmetic competencies among students with various types of learning difficulties (LD) and (2) to examine the influence of attention behaviors on possible group differences. Participants were a community sample of 291 third- and fourth-grade students with reading difficulties (RD) and/or math difficulties (MD), or with no LD (51 MD, 66 RD, 89 MD + RD, and 85 No LD students). Students were administered computerized measures of cognitive addition, subtraction, and estimation (accuracy and response times), as well as other measures. Groups were compared with and without covariation for behavioral inattention and their interactions. Small sums addition, thought to reflect retrieval processes, estimation accuracy, and number knowledge, did not show differences between MD and MD + RD students, although both showed lower performance than the RD and No LD groups. Attention behavior had a variable impact, most typically making group differences larger, but did not alter the general pattern of group differences, except in the case of estimation. [source]

ORIGINAL RESEARCH,ENDOCRINOLOGY: Pulse Pressure, an Index of Arterial Stiffness, Is Associated with Androgen Deficiency and Impaired Penile Blood Flow in Men with ED

THE JOURNAL OF SEXUAL MEDICINE, Issue 1 2009
Giovanni Corona MD
ABSTRACT Introduction., Pulse pressure (PP; i.e., the arithmetic difference between systolic and diastolic blood pressure) reflects arterial stiffness and has been suggested to be an independent cardiovascular risk factor. Aim., The aim of the present study is to asses the possible contribution of PP to arteriogenic erectile dysfunction (ED) and ED-associated hypogonadism. Methods., A consecutive series of 1,093 (mean age 52.1 ± 13.0 years) male patients with ED and without a previous history of hypertension or not taking any antihypertensive drugs were investigated. Main Outcome Measures., Several hormonal and biochemical parameters were studied, along with structured interview on erectile dysfunction (SIEDY), ANDROTEST structured interviews, and penile Doppler ultrasound. Results., Subjects with higher PP quartiles showed worse erectile function and higher prevalence of arteriogenic ED even after adjustment for confounding factors. Furthermore, sex hormone binding globulin-unbound testosterone levels declined as a function of PP quartiles. Accordingly, the prevalence of overt hypogonadism (calculated free testosterone < 180 pmol/L or free testosterone < 37 pmol/L) increased as a function of PP quartiles (17.% vs. 39.7%, and 30.8% vs. 58.6% for the first vs. fourth quartile, respectively, for calculated free testosterone and free testosterone; all P < 0.0001 for trend). This association was confirmed even after adjustment for confounders (Adjusted [Adj]) r = 0.090 and 0.095 for calculated free testosterone < 180 pmol/L and free testosterone < 37 pmol/L, respectively; all P < 0.05). Conclusions., PP is an easy method to estimate and quantify patient arterial stiffness. We demonstrated here for the first time that elevated PP is associated with arteriogenic ED and male hypogonadism. The calculation of PP should became more and more familiar in the clinical practice of health care professionals involved in sexual medicine. Corona G, Mannucci E, Lotti F, Fisher AD, Bandini E, Balercia G, Forti G, and Maggi M. Pulse pressure, an index of arterial stiffness, is associated with androgen deficiency and impaired penile blood flow in men with ED. J Sex Med 2009;6:285,293. [source]

Resource quality and stoichiometric constraints on stream ecosystem functioning

FRESHWATER BIOLOGY, Issue 5 2009
SALLY HLADYZ
Summary 1. Resource quality and stoichiometric imbalances in carbon : nutrient ratios between consumers and resources can influence key ecosystem processes. In many streams, this has important implications for food webs that are based largely upon the utilization of terrestrial leaf-litter, which varies widely among litter types in its value as a food source for detritivores and as a substrate for microbial decomposers. 2. We measured breakdown rates and macroinvertebrate colonization of leaf-litter from a range of native and exotic plants of differing resource quality and palatability to consumers [e.g. carbon : nitrogen : phosphorus (C : N : P) ratios, lignin and cellulose content], in a field experiment. We also measured C : N : P ratios of the principal leaf-shredding invertebrates, which revealed strong stoichiometric imbalances across trophic levels: C : N and C : P ratios typically differed by at least one order of magnitude between consumers and resources, whereas N : P imbalances were less marked. Application of the threshold elemental ratio approach, which integrates animal bioenergetics and body elemental composition in examining nutrient deficiency between consumers and resources, revealed less marked C : P imbalances than those based on the simpler arithmetic differences described above. 3. Litter breakdown rates declined as nutrient imbalances widened and resource quality fell, but they were independent of whether resources were exotic or native. The principal drivers of total, microbial and invertebrate-mediated breakdown rates were lignin : N, lignin : P and fungal biomass, respectively. However, multiple regression using orthogonal predictors yielded even more efficient models of litter breakdown, as consumers responded to more than one aspect of resource quality. For example, fungal biomass and litter C : N both influenced invertebrate-mediated breakdown. 4. Large stoichiometric imbalances and changes in resource quality are likely to have serious consequences for stream ecosystem functioning, especially when riparian zones have been invaded by exotic plant species whose chemical composition differs markedly from that of the native flora. Consequently, the magnitude and direction of change in breakdown rates and, thus, resource depletion, will be driven to a large extent by the biochemical traits (rather than taxonomic identity per se) of the resident and invading flora. [source]

Consequences for biodiversity of reducing inputs to upland temperate pastures: effects on beetles (Coleoptera) of cessation of nitrogen fertilizer application and reductions in stocking rates of sheep

GRASS & FORAGE SCIENCE, Issue 2 2004
P. Dennis
Abstract Current policies for upland pasture management in the UK encourage the integration of environmental objectives with livestock production through extensification of grazing systems. This study tested the hypothesis that a greater sward height in the summer would increase the diversity and abundance of grassland beetles (Coleoptera) as has been demonstrated for insects of indigenous grasslands. The hypothesis was tested with an experiment on an upland sheep pasture in mid-Wales. Experimental treatments received different nitrogen fertilizer inputs (0 or 50 kg ha,1), sheep stocking densities (12 or 9 ewes ha,1) and average sward heights in summer were constrained to 3·5 or 5·5 cm by conserving surplus grass for silage in subplots. Five treatments, replicated in three randomized blocks, combined the two stocking densities and two sward heights without nitrogen fertilizer inputs, with the fifth combining the higher stocking density, shortest sward height and the nitrogen fertilizer input. Beetles were sampled with twelve pitfall traps in each of the fifteen plots from June to September in 1993 and 1995. In years 1 (1993) and 3 (1995) of the experiment, more Coleoptera species occurred in the tall sward (an average of nine species in addition to the forty-one species present in the sward with the conventional sward height). Continuously grazed as opposed to ensiled subplots supported more beetle species but fewer individuals. Species composition of ground (Carabidae) and rove (Staphylinidae) beetles varied between treatments more than the arithmetic differences in species number. The experimental results supported the hypothesis but the benefits of taller swards to species diversity were small in the sown pastures of the study compared with indigenous upland grasslands (c. 33% fewer species). Inheritance effects of drainage, fertilizer and lime inputs, and the different species and management of cultivated pastures, may constrain the conservation benefits of altered pasture management compared with indigenous grasslands. [source]