170 research outputs found

    One path or two: Could differential grammatical class processing reflect human language evolution?

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    The fundamentally transient nature of human speech and sign means that there is no direct fossil record to document the emergence of language. As a result, theories of language evolution have traditionally relied on educated guesswork informed by child language acquisition studies and comparisons with other species' vocal communication systems. More recently, however, more refined language evolution models have been proposed from three general perspectives: the proto-speech model which assumes that spoken language first emerged as a communicative system in humans; the proto-sign model which broadly assumes that language first emerged in the form of manual gesture; and the mixed or co-evolution model which posits both sound and gesture components. Although there is a vast pool of literature examining the neural bases of modern human language which has, in turn, been interpreted from a language evolution perspective, many of these studies have used methodologies which could have potentially confounded results. The current thesis was therefore firstly designed to address such concerns by establishing a corpus of experimental stimulus words in which both cognitive and acoustic properties were quantified and therefore controllable. Having thus established this corpus, electroencephalography (EEG) was recorded from 30 human participants as they undertook (i) a passive listening task involving animal vocalisations and (ii) a grammatical decision/learning task (nouns versus verbs) using real and nonsense human speech stimuli. Results suggested that within the adult human brain, changes in both the lower (8 - 10 Hz) and upper (10 - 12 Hz) alpha EEG range reflect functional differences in the processing of complex communicative sound strings, with spoken noun and verb stimuli showing clearly distinct patterns of information processing flow. Of note, the left frontal eye field appears to process verb but not noun stimuli on-the-fly. Furthermore, differences in grammatical class processing (nouns versus verbs) appear to occur early

    On the Influence of Alloy Composition on the Additive Manufacturability of Ni-Based Superalloys

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    The susceptibility of nickel-based superalloys to processing-induced crack formation during laser powder-bed additive manufacturing is studied. Twelve different alloys—some of existing (heritage) type but also other newly-designed ones—are considered. A strong inter-dependence of alloy composition and processability is demonstrated. Stereological procedures are developed to enable the two dominant defect types found—solidification cracks and solid-state ductility dip cracks—to be distinguished and quantified. Differential scanning calorimetry, creep stress relaxation tests at 1000 °C and measurements of tensile ductility at 800 °C are used to interpret the effects of alloy composition. A model for solid-state cracking is proposed, based on an incapacity to relax the thermal stress arising from constrained differential thermal contraction; its development is supported by experimental measurements using a constrained bar cooling test. A modified solidification cracking criterion is proposed based upon solidification range but including also a contribution from the stress relaxation effect. This work provides fundamental insights into the role of composition on the additive manufacturability of these materials

    Resveratrol: A potential hippocampal plasticity enhancer

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    The search for molecules capable of restoring altered hippocampal plasticity in psychiatric and neurological conditions is one of the most important tasks of modern neuroscience. It is well established that neural plasticity, such as the ability of the postnatal hippocampus to continuously generate newly functional neurons throughout life, a process called adult hippocampal neurogenesis (AHN), can be modulated not only by pharmacological agents, physical exercise, and environmental enrichment, but also by “nutraceutical” agents. In this review we focus on resveratrol, a phenol and phytoalexin found in the skin of grapes and red berries, as well as in nuts. Resveratrol has been reported to have antioxidant and antitumor properties, but its effects as a neural plasticity inducer are still debated. The current review examines recent evidence implicating resveratrol in regulating hippocampal neural plasticity and in mitigating the effects of various disorders and diseases on this important brain structure. Overall, findings show that resveratrol can improve cognition and mood and enhance hippocampal plasticity and AHN; however, some studies report opposite effects, with resveratrol inhibiting aspects of AHN. Therefore, further investigation is needed to resolve these controversies before resveratrol can be established as a safe coadjuvant in preventing and treating neuropsychiatric conditions

    Psychosis risk candidate ZNF804A localizes to synapses and regulates neurite formation and dendritic spine structure

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    BackgroundVariation in the gene encoding zinc finger binding protein 804A (ZNF804A) is associated with schizophrenia (SCZ) and bipolar disorder (BP). Evidence suggests that ZNF804A is a regulator of gene transcription and is present in nuclear and extranuclear compartments. However, a detailed examination of ZNF804A distribution and its neuronal functions has yet to be performed.MethodsThe localization of ZNF804A protein was examined in neurons derived from human neural progenitor cells (hNPCs), human induced pluripotent stem cells (hiPSCs) or in primary rat cortical neurons. Additionally, siRNA-mediated knockdown of ZNF804A was conducted to determine its role in neurite formation, maintenance of dendritic spine morphology and responses to activity-dependent stimulations.ResultsEndogenous ZNF804A protein localized to somato-dendritic compartments and co-localized with the putative synaptic markers in young neurons derived from hNPCs and hiPSCs. In mature rat neurons, Zfp804A, the homolog of ZNF804A, was present in a subset of dendritic spines and co-localized with synaptic proteins in specific nanodomains, as determined by superresolution microscopy. Interestingly, knockdown of ZNF804A attenuated neurite outgrowth in young neurons, an effect potentially mediated by reduced neuroligin-4 (NLGN4) expression. Furthermore, knockdown of ZNF804A in mature neurons resulted in the loss of dendritic spine density, and impaired responses to activity-dependent stimulation.ConclusionsThese data reveal a novel subcellular distribution for ZNF804A within somato-dendritic compartments and a nanoscopic organisation at excitatory synapses. Moreover, our results suggest that ZNF804A plays an active role in neurite formation, maintenance of dendritic spines and activity-dependent structural plasticity

    Application of species distribution models and conservation planning software to the design of a reserve network for the riverine fishes of northeastern Mesoamerica

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    1. Protected area networks for river ecosystems must account for the highly connected nature of river habitats and the fact that conditions in distant locations can influence downstream habitats and biota. We used Marxan conservation planning software to address the unique constraints of reserve design in river ecosystems and structure a reserve network to overcome key challenges to freshwater conservation.2. The range limits of 63 fish species in Mesoamerica were predicted and used in Marxan to design a network of conservation focal areas that encompasses 15% of the range of each species in areas with low risk of environmental degradation. Upstream risk intensity was estimated by propagating landscape-based sources of stress downstream along the direction of flow in GIS. We constrained Marxan solutions to account for basin divides, and we defined critical management zones to include important habitats that contribute to species persistence and mitigate threats.3. The proposed reserve network encompassed 11% of the study area, half of which was contained within existing protected areas. Our exercise also identified important gaps in protection. Because terrestrial-based environmental risks were propagated through the river network and considered in the solution, focal areas were constrained to catchments with low levels of upstream human activity. Addition of critical management zones – riparian buffers and fish migration corridors – expanded the network area by one-fifth.4. Our application of Marxan allowed longitudinal connectivity and topographic barriers to species movement to be considered. Adding critical management zones expanded the size of the reserve network, but is crucial to the network’s conservation efficacy. We call for an evaluation of the added management capacity needed to conserve critical management zones and suggest ways to further improve the reserve design process.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/79354/1/j.1365-2427.2010.02417.x.pd

    Multi-Jet Event Rates in Deep Inelastic Scattering and Determination of the Strong Coupling Constant

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    Jet event rates in deep inelastic ep scattering at HERA are investigated applying the modified JADE jet algorithm. The analysis uses data taken with the H1 detector in 1994 and 1995. The data are corrected for detector and hadronization effects and then compared with perturbative QCD predictions using next-to-leading order calculations. The strong coupling constant alpha_S(M_Z^2) is determined evaluating the jet event rates. Values of alpha_S(Q^2) are extracted in four different bins of the negative squared momentum transfer~\qq in the range from 40 GeV2 to 4000 GeV2. A combined fit of the renormalization group equation to these several alpha_S(Q^2) values results in alpha_S(M_Z^2) = 0.117+-0.003(stat)+0.009-0.013(syst)+0.006(jet algorithm).Comment: 17 pages, 4 figures, 3 tables, this version to appear in Eur. Phys. J.; it replaces first posted hep-ex/9807019 which had incorrect figure 4

    Measurement of Leading Proton and Neutron Production in Deep Inelastic Scattering at HERA

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    Deep--inelastic scattering events with a leading baryon have been detected by the H1 experiment at HERA using a forward proton spectrometer and a forward neutron calorimeter. Semi--inclusive cross sections have been measured in the kinematic region 2 <= Q^2 <= 50 GeV^2, 6.10^-5 <= x <= 6.10^-3 and baryon p_T <= MeV, for events with a final state proton with energy 580 <= E' <= 740 GeV, or a neutron with energy E' >= 160 GeV. The measurements are used to test production models and factorization hypotheses. A Regge model of leading baryon production which consists of pion, pomeron and secondary reggeon exchanges gives an acceptable description of both semi-inclusive cross sections in the region 0.7 <= E'/E_p <= 0.9, where E_p is the proton beam energy. The leading neutron data are used to estimate for the first time the structure function of the pion at small Bjorken--x.Comment: 30 pages, 9 figures, 2 tables, submitted to Eur. Phys.

    Gender and release from imprisonment: Convict licensing systems in mid to late 19th century England

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    This paper draws on the research undertaken into the lives and prison experiences of around 650 male and female convicts who were released on licence (an early form of parole) from sentences of long term imprisonment (three years to life) in England in the mid- to late-nineteenth century. Our project confirmed the patterns of offending seen in other studies of female and male offending, namely, that women were committed to periods of long-term imprisonment overwhelmingly for crimes of larceny and sometimes low-level violence (or their criminal backgrounds indicated this type of low-level disorderly behaviour) and only in the minority for crimes of serious interpersonal violence. Similarly, the majority of men were also committed to the convict system for larceny. Yet how male and female offenders were treated by the prison licensing system did differ significantly. The vast majority of all prisoners, male and female, were released early on licence from their prison terms, even those who had committed very serious offences. All licences had several conditions in them and licence-holders were free so long as they met these conditions. Any breach of the above conditions meant that the individual would be returned to prison to serve out the remainder of their sentence.However, a proportion of female offenders were released slightly earlier than their male counterparts, though not directly into the community but on a conditional licence to Female Refuges. Out of the 288 women researched in our project, 200 of them were released in this manner; under further confinement in a refuge. Women stayed in such refuges for on average between six and nine months, before their final release was then approved by the Directors of the Convict Prisons
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