Determination of Young's and shear moduli of common yew and Norway spruce by means of ultrasonic waves

Despite the exceptional position of yew among the gymnosperms concerning its elastomechanical properties, no reference values for its elastic constants apart from the longitudinal Young's modulus have been available from literature so far. Hence, this study's objective was to determine the Young's moduli E L, E R and E T and the shear moduli G LR, G LT and G RT of yew wood. For that purpose, we measured the ultrasound velocities of longitudinal and transversal waves applied to small cubic specimens and derived the elastic constants from the results. The tests were carried out at varying wood moisture contents and were applied to spruce specimens as well in order to put the results into perspective. Results indicate that E L is in the same order of magnitude for both species, which means that a high-density wood species like yew does not inevitably have to have a high longitudinal Young's modulus. For the transverse Young's moduli of yew, however, we obtained 1.5-2 times, for the shear moduli even 3-6 times higher values compared to spruce. The variation of moisture content primarily revealed differences between both species concerning the shear modulus of the RT plane. We concluded that anatomical features such as the microfibril angle, the high ray percentage and presumably the large amount of extractives must fulfil important functions for the extraordinary elastomechanical behaviour of yew wood which still has to be investigated in subsequent micromechanical studie

Large-scale Acoustic Analysis of Dialectal and Social Factors in English /s/-retraction

The retraction of /s/ in /str/, eg street, is a sound change found in certain English dialects. Previous work suggests that /s/-retraction arises from lower spectral frequency /s/ in /str/. The extent to which /s/-retraction differs across English dialects is unclear. This paper presents results from a large-scale, acoustic phonetic study of sibilants in 420 speakers, from 6 spontaneous speech corpora (9 dialects) of North American and Scottish English. Spectral Centre of Gravity was modelled from automatic measures of word-initial sibilants. Female speakers show higher frequency sibilants than males, but more so for /s/ than /S/; /s/ is also higher in American than Canadian/Scottish dialects; /S/ is surprisingly variable. /s/-retraction, modelled as retraction ratios, is generally greater for /str/ than /spr skr/, but varies by dialect; females show more retraction in /str/ than males. Dialectal and social factors clearly influence /s/-retraction in English clusters /sp st sk/, /spr skr/, and /str/

Age Vectors vs. Axes of Intraspeaker Variation in Vowel Formants Measured Automatically From Several English Speech Corpora

To test the hypothesis that intraspeaker variation in vowel formants is related to the direction of diachronic change, we compare the direction of change in apparent time with the axis of intraspeaker variation in F1 and F2 for vowel phonemes in several corpora of North American and Scottish English. These vowels were measured automatically with a scheme (tested on hand-measured vowels) that considers the frequency, bandwidth, and amplitude of the first three formants in reference to a prototype. In the corpus data, we find that the axis of intraspeaker variation is typically aligned vertically, presumably corresponding to the degree of jaw opening for individual tokens, but for the North American GOOSE vowel, the axis of intraspeaker variation is aligned with the (horizontal) axis of diachronic change for this vowel across North America. This may help to explain why fronting and unrounding of high back vowels are common shifts across languages

A Direct Interaction of Axonin-1 with NgCAM-related Cell Adhesion Molecule (NrCAM) Results in Guidance, but not Growth of Commissural Axons

An interaction of growth cone axonin-1 with the floor-plate NgCAM-related cell adhesion molecule (NrCAM) was shown to play a crucial role in commissural axon guidance across the midline of the spinal cord. We now provide evidence that axonin-1 mediates a guidance signal without promoting axon elongation. In an in vitro assay, commissural axons grew preferentially on stripes coated with a mixture of NrCAM and NgCAM. This preference was abolished in the presence of anti–axonin-1 antibodies without a decrease in neurite length. Consistent with these findings, commissural axons in vivo only fail to extend along the longitudinal axis when both NrCAM and NgCAM interactions, but not when axonin-1 and NrCAM or axonin-1 and NgCAM interactions, are perturbed. Thus, we conclude that axonin-1 is involved in guidance of commissural axons without promoting their growth

Towards harmonizing natural resources as an area of protection in life cycle impact assessment

Purpose. In this paper, we summarize the discussion and present the findings of an expert group effort under the umbrella of the United Nations Environment Programme (UNEP)/Society of Environmental Toxicology and Chemistry (SETAC) Life Cycle Initiative proposing natural resources as an Area of Protection (AoP) in Life Cycle Impact Assessment (LCIA). Methods: As a first step, natural resources have been defined for the LCA context with reference to the overall UNEP/SETAC Life Cycle Impact Assessment (LCIA) framework. Second, existing LCIA methods have been reviewed and discussed. The reviewed methods have been evaluated according to the considered type of natural resources and their underlying principles followed (use-to-availability ratios, backup technology approaches, or thermodynamic accounting methods). Results and discussion. There is currently no single LCIA method available that addresses impacts for all natural resource categories, nor do existing methods and models addressing different natural resource categories do so in a consistent way across categories. Exceptions are exergy and solar energy-related methods, which cover the widest range of resource categories. However, these methods do not link exergy consumption to changes in availability or provisioning capacity of a specific natural resource (e.g., mineral, water, land etc.). So far, there is no agreement in the scientific community on the most relevant type of future resource indicators (depletion, increased energy use or cost due to resource extraction, etc.). To address this challenge, a framework based on the concept of stock/fund/flow resources is proposed to identify, across natural resource categories, whether depletion/dissipation (of stocks and funds) or competition (for flows) is the main relevant aspect. Conclusions. An LCIA method—or a set of methods—that consistently address all natural resource categories is needed in order to avoid burden shifting from the impact associated with one resource to the impact associated with another resource. This paper is an important basis for a step forward in the direction of consistently integrating the various natural resources as an Area of Protection into LCA

Coincident Pre- and Postsynaptic Activation Induces Dendritic Filopodia via Neurotrypsin-Dependent Agrin Cleavage

SummaryThe synaptic serine protease neurotrypsin is essential for cognitive function, as its deficiency in humans results in severe mental retardation. Recently, we demonstrated the activity-dependent release of neurotrypsin from presynaptic terminals and proteolytical cleavage of agrin at the synapse. Here we show that the activity-dependent formation of dendritic filopodia is abolished in hippocampal neurons from neurotrypsin-deficient mice. Administration of the neurotrypsin-dependent 22 kDa fragment of agrin rescues the filopodial response. Detailed analyses indicated that presynaptic action potential firing is necessary for the release of neurotrypsin, whereas postsynaptic NMDA receptor activation is necessary for the neurotrypsin-dependent cleavage of agrin. This contingency characterizes the neurotrypsin-agrin system as a coincidence detector of pre- and postsynaptic activation. As the resulting dendritic filopodia are thought to represent precursors of synapses, the neurotrypsin-dependent cleavage of agrin at the synapse may be instrumental for a Hebbian organization and remodeling of synaptic circuits in the CNS