1,770 research outputs found
Economic Value Added
Economic Value Added (EVA), when applied properly in a company, impacts all departments and decisions. The equation for EVA as well as the adjustments that must be made to current accounting practices is the basis for an understanding of EVA. The success of EVA is displayed as companies that have implemented EVA to varying degrees are compared with companies that have not implemented EVA. Once the argument for the overall superiority of EVA is made, traditional performance measures and current accounting practices are evaluated. Then, the importance of creating value within corporations becomes apparent. Finally, a detailed example of the implementation process that took place several years ago at Harsco argued in favor of all companies adopting EVA
Bridging a Complete Transection Lesion of Adult Rat Spinal Cord with Growth Factor-Treated Nitrocellulose Implants
The ability of a substrate bound
neurotrophic factor to promote growth of
ascending sensory axons across a complete
transection lesion of the rat spinal cord was
examined in a transplantation model. Aspiration
lesions created a 3 mm long cavity in the upper
lumbar spinal cord of adult rats. Five weeks
after injury two strips of nerve growth factortreated
nitrocellulose, were implanted, each in a
medio-lateral position, and apposed to the
rostral and caudal surfaces of the cavity.
Control animals received untreated nitrocellulose
implants. Fetal spinal cord tissue was
transplanted alongsideand between these strips.
Six weeks post transplantation, animals were
sacrificed and vibratome sections through the
grafts were processed for immunocytochemical
demonstration of ingrowing axons expressing
calcitonin gene-related peptide (CGRP-IR),
Immunolabeled axons were abundant at the
caudal interface between host tissue and the
NGF-treated nitrocellulose implants, with dense
fascicles of fibers abutting the grafts. As the
distance from the caudal surface increased some
CGRP-IR fibers extended into the fetal tissue
although most appeared to remain oriented in a
longitudinal course adjacent to the nitrocellulose.
Labeled axons were evident along the
entire length of the nitrocellulose and appeared
to aggregate at the rostral tip of the implant,
with many fibers extending into the host spinal
cord rostral to the lesion/transplant site. When
untreated nitrocellulose was implanted, fewer
labeled axons appeared to extend beyond the
caudal host-graft interface. Most CGRP-IR
axons displayed limited association or contact
with the untreated nitrocellulose in this
condition. Computer-assisted quantitative
analysis indicated that NGF-treated nitrocellulose
supported regrowing host axons for
nearly three times the length exhibited by axons
associated with non-treated nitrocellulose
implants. These results indicate that substrate
bound nerve growth factor has the capacity to
enhance the regrowth of ascending sensory
axons across a traumatic spinal cord injury site.
The potential to reestablish functional contacts
across such a lesion may be heightened by the
ability of neurotrophic factors to promote more
extensive axonal regrowth
Evolution of reduced post-copulatory molecular interactions in Drosophila populations lacking sperm competition.
In many species with internal fertilization, molecules transferred in the male ejaculate trigger and interact with physiological changes in females. It is controversial to what extent these interactions between the sexes act synergistically to mediate the female switch to a reproductive state or instead reflect sexual antagonism evolved as a by product of sexual selection on males. To address this question, we eliminated sexual selection by enforcing monogamy in populations of Drosophila melanogaster for 65 generations and then measured the expression of male seminal fluid protein genes and genes involved in the female response to mating. In the absence of sperm competition, male and female reproductive interests are perfectly aligned and any antagonism should be reduced by natural selection. Consistent with this idea, males from monogamous populations showed reduced expression of seminal fluid protein genes, 16% less on average than in polygamous males. Further, we identified 428 genes that responded to mating in females. After mating, females with an evolutionary history of monogamy exhibited lower relative expression of genes that were up regulated in response to mating and higher expression of genes that were down-regulated - in other words, their post-mating transcriptome appeared more virgin-like. Surprisingly, these genes showed a similar pattern even before mating, suggesting that monogamous females evolved to be less poised for mating and the accompanying receipt of male seminal fluid proteins. This reduced investment by both monogamous males and females in molecules involved in post-copulatory interactions points to a pervasive role of sexual conflict in shaping these interactions
Recommended from our members
Permeation of CO₂ and N₂ through glassy poly(dimethyl phenylene) oxide under steady- and presteady-state conditions
Glassy polymers are often used for gas separations because of their high selectivity. Although the dual‐mode permeation model correctly fits their sorption and permeation isotherms, its physical interpretation is disputed, and it does not describe permeation far from steady state, a condition expected when separations involve intermittent renewable energy sources. To develop a more comprehensive permeation model, we combine experiment, molecular dynamics, and multiscale reaction–diffusion modeling to characterize the time‐dependent permeation of N₂ and CO₂ through a glassy poly(dimethyl phenylene oxide) membrane, a model system. Simulations of experimental time‐dependent permeation data for both gases in the presteady‐state and steady‐state regimes show that both single‐ and dual‐mode reaction–diffusion models reproduce the experimental observations, and that sorbed gas concentrations lag the external pressure rise. The results point to environment‐sensitive diffusion coefficients as a vital characteristic of transport in glassy polymers
Soil weathering rates in 21 catchments of the Canadian Shield
Soil mineral weathering represents an essential source of nutrient base cation (Ca, Mg and K) for forest growth in addition to provide a buffering power against precipitation acidity for soils and surface waters. Weathering rates of base cations were obtained for 21 catchments located within the temperate and the boreal forest of the Canadian Shield with the geochemical model PROFILE. Weathering rates ranged from 0.58 to 4.46 kmol<sub>c</sub> ha<sup>−1</sup> yr<sup>−1</sup> and their spatial variation within the studied area was mostly in agreement with spatial variations in soil mineralogy. Weathering rates of Ca and Mg were significantly correlated (<i>r</i> = 0.80 and 0.64) with their respective lake concentrations. Weathering rates of K and Na did not correlate with lake concentrations of K and Na. The modeled weathering rates for each catchment were also compared with estimations of net catchment exportations. The result show that modeled weathering rates of Ca were not significantly different than the net catchment exportations while modeled weathering rates of Mg were higher by 51%. Larger differences were observed for K and Na weathering rates that were significantly different than net catchment exportations being 6.9 and 2.2 times higher than net exportations, respectively. The results for K were expected given its high reactivity with biotic compartments and suggest that most of the K produced by weathering reactions was retained within soil catchments and/or above ground biomass. This explanation does not apply to Na, however, which is a conservative element in forest ecosystems because of the insignificant needs of Na for soil microorganisms and above ground vegetations. It raises concern about the liability of the PROFILE model to provide reliable values of Na weathering rates. Overall, we concluded that the PROFILE model is powerful enough to reproduce spatial geographical gradients in weathering rates for relatively large areas as well as adequately predict absolute weathering rates values for the sum of base cations, Ca and Mg
Direct Estimation of the Mitochondrial DNA Mutation Rate in Drosophila melanogaster
Mitochondrial DNA (mtDNA) variants are widely used in evolutionary genetics as markers for population history and to estimate divergence times among taxa. Inferences of species history are generally based on phylogenetic comparisons, which assume that molecular evolution is clock-like. Between-species comparisons have also been used to estimate the mutation rate, using sites that are thought to evolve neutrally. We directly estimated the mtDNA mutation rate by scanning the mitochondrial genome of Drosophila melanogaster lines that had undergone approximately 200 generations of spontaneous mutation accumulation (MA). We detected a total of 28 point mutations and eight insertion-deletion (indel) mutations, yielding an estimate for the single-nucleotide mutation rate of 6.2 × 10−8 per site per fly generation. Most mutations were heteroplasmic within a line, and their frequency distribution suggests that the effective number of mitochondrial genomes transmitted per female per generation is about 30. We observed repeated occurrences of some indel mutations, suggesting that indel mutational hotspots are common. Among the point mutations, there is a large excess of G→A mutations on the major strand (the sense strand for the majority of mitochondrial genes). These mutations tend to occur at nonsynonymous sites of protein-coding genes, and they are expected to be deleterious, so do not become fixed between species. The overall mtDNA mutation rate per base pair per fly generation in Drosophila is estimated to be about 10× higher than the nuclear mutation rate, but the mitochondrial major strand G→A mutation rate is about 70× higher than the nuclear rate. Silent sites are substantially more strongly biased towards A and T than nonsynonymous sites, consistent with the extreme mutation bias towards A+T. Strand-asymmetric mutation bias, coupled with selection to maintain specific nonsynonymous bases, therefore provides an explanation for the extreme base composition of the mitochondrial genome of Drosophila
Patterns of environmental variance across environments and traits in domestic cattle
The variance in phenotypic trait values is a product of environmental and genetic variation. The sensitivity of traits to environmental variation has a genetic component and is likely to be under selection. However, there are few studies investigating the evolution of this sensitivity, in part due to the challenges of estimating the environmental variance. The livestock literature provides a wealth of studies that accurately partition components of phenotypic variance, including the environmental variance, in well-defined environments. These studies involve breeds that have been under strong selection on mean phenotype in optimal environments for many generations, and therefore represent an opportunity to study the potential evolution of trait sensitivity to environmental conditions. Here, we use literature on domestic cattle to examine the evolution of micro-environmental variance (CVR-the coefficient of residual variance) by testing for differences in expression of CVR in animals from the same breed reared in different environments. Traits that have been under strong selection did not follow a null expectation of an increase in CVR in heterogenous environments (e.g., grazing), a pattern that may reflect evolution of increased uniformity in heterogeneous environments. When comparing CVR across environments of different levels of optimality, here measured by trait mean, we found a reduction in CVR in the more optimal environments for both life history and growth traits. Selection aimed at increasing trait means in livestock breeds typically occurs in the more optimal environments, and we therefore suspect that the decreased CVR is a consequence of evolution of the expression of micro-environmental variance in this environment. Our results highlight the heterogeneity in micro-environmental variance across environments and point to possible connections to the intensity of selection on trait means
Heritability of female extra-pair paternity rate in song sparrows (Melospiza melodia)
The forces driving the evolution of extra-pair reproduction in socially monogamous animals remain widely debated and unresolved. One key hypothesis is that female extra-pair reproduction evolves through indirect genetic benefits, reflecting increased additive genetic value of extra-pair offspring. Such evolution requires that a female's propensity to produce offspring that are sired by an extra-pair male is heritable. However, additive genetic variance and heritability in female extra-pair paternity (EPP) rate have not been quantified, precluding accurate estimation of the force of indirect selection. Sixteen years of comprehensive paternity and pedigree data from socially monogamous but genetically polygynandrous song sparrows (Melospiza melodia) showed significant additive genetic variance and heritability in the proportion of a female's offspring that was sired by an extra-pair male, constituting major components of the genetic architecture required for extra-pair reproduction to evolve through indirect additive genetic benefits. However, estimated heritabilities were moderately small (0.12 and 0.18 on the observed and underlying latent scales, respectively). The force of selection on extra-pair reproduction through indirect additive genetic benefits may consequently be relatively weak. However, the additive genetic variance and non-zero heritability observed in female EPP rate allow for multiple further genetic mechanisms to drive and constrain mating system evolution
Perceptions of U.S. and Canadian maple syrup producers toward climate change, its impacts, and potential adaptation measures
The production of maple syrup is an important cultural and economic activity directly related to the climate of northeastern North America. As a result, there are signs that climate change could have negative impacts on maple syrup production in the next decades, particularly for regions located at the southern margins of the sugar maple (Acer saccharum Marsh.) range. The purpose of this survey study is to present the beliefs and opinions of maple syrup producers of Canada (N = 241) and the U.S. (N = 113) on climate change in general, its impacts on sugar maple health and maple syrup production, and potential adaptation measures. Using conditional inference classification trees, we examined how the socio-economic profile of respondents and the geographic location and size of respondents’ sugar bushes shaped the responses of survey participants. While a majority (75%) of respondents are confident that the average temperature on Earth is increasing, less than half (46%) believe that climate change will have negative impacts on maple syrup yield in the next 30 years. Political view was a significant predictor of these results, with respondents at the right right and center-right of the political spectrum being less likely to believe in climate change and less likely to anticipate negative effects of climate change on maple syrup production. In addition, 77% of the participants indicated an interest in adopting adaptation strategies if those could increase maple syrup production. This interest was greater for respondents using vacuum tubing for sap collection than other collection methods. However, for many respondents (particularly in Canada), lack of information was identified as a constraint limiting adaptation to climate change.SL and AP were partly funded by the CICan Career-Launcher Internship program. AA was supported by Spanish Government through the Juan de la Cierva fellowship program (IJCI- 2016-30049)
Geometric Path Integrals. A Language for Multiscale Biology and Systems Robustness
In this paper we suggest that, under suitable conditions, supervised learning
can provide the basis to formulate at the microscopic level quantitative
questions on the phenotype structure of multicellular organisms. The problem of
explaining the robustness of the phenotype structure is rephrased as a real
geometrical problem on a fixed domain. We further suggest a generalization of
path integrals that reduces the problem of deciding whether a given molecular
network can generate specific phenotypes to a numerical property of a
robustness function with complex output, for which we give heuristic
justification. Finally, we use our formalism to interpret a pointedly
quantitative developmental biology problem on the allowed number of pairs of
legs in centipedes
- …