Cortical and spinal mechanisms of task failure of sustained submaximal fatiguing contractions

In this and the subsequent companion paper, results are presented that collectively seek to delineate the contribution that supraspinal circuits have in determining the time to task failure (TTF) of sustained submaximal contractions. The purpose of this study was to compare adjustments in supraspinal and spinal excitability taken concurrently throughout the performance of two different fatigue tasks with identical mechanical demands but different TTF (i.e., force-matching and position-matching tasks). On separate visits, ten healthy volunteers performed the force-matching or position-matching task at 15% of maximum strength with the elbow flexors to task failure. Single-pulse transcranial magnetic stimulation (TMS), paired-pulse TMS, paired cortico-cervicomedullary stimulation, and brachial plexus electrical stimulation were delivered in a 6-stimuli sequence at baseline and every 2–3 minutes throughout fatigue-task performance. Contrary to expectations, the force-matching task TTF was 42% shorter (17.5±7.9 min) than the position-matching task (26.9±15.11 min; p0.05). Therefore, failure occurred after a similar mean decline in motorneuron excitability developed (p0.10) and an index of upstream excitation of the motor cortex remained constant (p>0.40). Together, these results suggest that as fatigue develops prior to task failure, the increase in corticospinal excitability observed in relationship to the decrease in spinal excitability results from a combination of decreasing intracortical inhibition with constant levels of intracortical facilitation and upstream excitability that together eventually fail to provide the input to the motor cortex necessary for descending drive to overcome the spinal cord resistance, thereby contributing to task failure

Did aid promote democracy in Africa?: the role of technical assistance in Africa’s transitions

Did foreign aid impede or catalyze democratization in Africa in the 1990s? We argue that after the Cold War, donors increased their use of technical assistance in aid packages, improving their monitoring capacity and thus reducing autocrats’ ability to use aid for patronage. To remain in power, autocrats responded by conceding political rights to their opponents—from legalizing opposition parties to staging elections. We test our theory with panel data for all sub-Saharan African countries. While other factors played pivotal roles in Africa’s political liberalization, we find technical assistance helps to explain the timing and extent of Africa’s democratization

Translanguaging Supports Reading with Deaf Adult Bilinguals: A Qualitative Approach

Translanguaging is a pedagogical theory and an approach to teaching language. It conceptualizes the dynamic ways in which bilinguals use their linguistic repertoire and language practices in both languages for learning, meaning-making, reading, and writing. This study reports on the results of a qualitative study using Grounded Theory. The research question posed was, “what insights do bilingual Deaf readers provide regarding their metalinguistic processes and reading strategies used during translanguaging? To answer this question, responses were gathered from Deaf adults who were interviewed on their language and literacy histories. Further, they were queried about their reading comprehension practices using translanguaging. The researchers used videotaped interviews taken in American Sign Language (ASL) then glossed into English for analyses to examine how Deaf adults comprehended English expository texts. Based on the data analysis, the core category, “bridge to literacy” was revealed after identifying seven themes. Recommendations for future research using the translanguaging bilingual theory and practice are included

Research and Development of the eXtendable Solar Array System

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97139/1/AIAA2012-143.pd

Health assessment of gasoline and fuel oxygenate vapors: Micronucleus and sister chromatid exchange evaluations

AbstractMicronucleus and sister chromatid exchange (SCE) tests were performed for vapor condensate of baseline gasoline (BGVC), or gasoline with oxygenates, methyl tert-butyl ether (G/MTBE), ethyl tert butyl ether (G/ETBE), t-amyl methyl ether (G/TAME), diisopropyl ether (G/DIPE), t-butyl alcohol (TBA), or ethanol (G/EtOH). Sprague Dawley rats (the same 5/sex/group for both endpoints) were exposed to 0, 2000, 10,000, or 20,000mg/m3 of each condensate, 6h/day, 5days/week over 4weeks. Positive controls (5/sex/test) were given cyclophosphamide IP, 24h prior to sacrifice at 5mg/kg (SCE test) and 40mg/kg (micronucleus test). Blood was collected from the abdominal aorta for the SCE test and femurs removed for the micronucleus test. Blood cell cultures were treated with 5μg/ml bromodeoxyuridine (BrdU) for SCE evaluation. No significant increases in micronucleated immature erythrocytes were observed for any test material. Statistically significant increases in SCE were observed in rats given BGVC alone or in female rats given G/MTBE. G/TAME induced increased SCE in both sexes at the highest dose only. Although DNA perturbation was observed for several samples, DNA damage was not expressed as increased micronuclei in bone marrow cells. Inclusion of oxygenates in gasoline did not increase the effects of gasoline alone or produce a cytogenetic hazard

Thin Fisher Zeroes

Biskup et al. [Phys. Rev. Lett. 84 (2000) 4794] have recently suggested that the loci of partition function zeroes can profitably be regarded as phase boundaries in the complex temperature or field planes. We obtain the Fisher zeroes for Ising and Potts models on non-planar (``thin'') regular random graphs using this approach, and note that the locus of Fisher zeroes on a Bethe lattice is identical to the corresponding random graph. Since the number of states appears as a parameter in the Potts solution the limiting locus of chromatic zeroes is also accessible.Comment: 10 pages, 4 figure

Editorial: Polar genomics in a changing world

Polar regions play critical roles in the function of the Earth’s climate system, many of which are underpinned by their endemic biota. Whilst being home to some of the world’s best-known charismatic megafauna such as polar bears, whales, penguins, seals and albatrosses, polar regions also harbour some of the most poorly explored and least understood biodiversity on the planet (https://www.ipcc.ch/reports, accessed on 9 June 2023). Moreover, these regions are amongst those areas of our planet experiencing the most rapid rates of warming [1,2], resulting in severe threats to their unique ecosystems [3]. With regional warming, the organisms living in these frozen ecosystems will have to adapt if they are to survive, yet we currently have a very limited understanding of polar biodiversity, or indeed of the future resilience of polar organisms in our changing world. To generate a priori predictions of biodiversity change in these regions, it is imperative to understand the true extent of polar biodiversity, including how organisms interact (for example, in food webs), the biological mechanisms by which they have adapted to polar environments, their levels of phenotypic plasticity, and how these attributes may impact their abilities to respond to change. Critical to this understanding are “genomics” approaches that exploit the high-throughput sequencing of genetic material. With the costs of sequencing DNA and RNA having decreased dramatically over recent years, our abilities to probe the genetic code of polar organisms have expanded immeasurably, such that we are now able to answer ecological and evolutionary questions that were intractable even a few years ago, as exemplified by the contributions in this Special Issue on polar genomics

Evidence for unusual spatial location coding in Williams syndrome: An explanation for the local bias in visuo-spatial construction tasks?

Individuals with Williams syndrome (WS) display poor visuo-spatial cognition relative to verbal abilities. Furthermore, whilst perceptual abilities are delayed, visuo-spatial construction abilities are comparatively even weaker, and are characterised by a local bias. We investigated whether this differentiation in visuo-spatial abilities can be explained by a deficit in coding spatial location in WS. This can be measured by assessing participants? understanding of the spatial relations between objects within a visual scene. Coordinate and categorical spatial relations were investigated independently in four participant groups: 21 individuals with WS; 21 typically developing (TD) children matched for non-verbal ability; 20 typically developing controls of a lower non-verbal ability; and 21 adults. A third task measured understanding of visual colour relations. Results indicated first, that the comprehension of categorical and co-ordinate spatial relations is equally poor in WS. Second, that the comprehension of visual relations is also at an equivalent level to spatial relational understanding in this population. These results can explain the difference in performance on visuo-spatial perception and construction tasks in WS. In addition, both the WS and control groups displayed response biases in the spatial tasks. However, the direction of bias differed across the groups. This finding is explored in relation to current theories of spatial location coding