161,322 research outputs found
Arctic Ocean Shipping Navigation, Security and Sovereignty in the North American Arctic
No full textIn Arctic Ocean Shipping, Donald R. Rothwell assesses contemporary navigation, security and sovereignty issues in the North American Arctic. Shipping in the Arctic Ocean is becoming a critical legal, geopolitical and security issue as a result of climate change and increased interest from non-Arctic States such as China. The law of the sea provides the key legal framework for the regulation of Arctic Ocean shipping, and has been relied upon by Canada and the United States to develop the legal regime for the Northwest Passage and the Bering Strait. Navigation within the EEZ and high seas in the Arctic is also becoming more strategically significant as a result of climate change. Multiple issues are raised with respect to maritime security and the adequacy of the existing legal regime, including how Canada and the United States will respond to interest being expressed in Arctic shipping by Asian States
Donald R Rothwell & Tim Stephens, The International Law of the Sea (London: Bloomsbury, 2016, 2nd ed.)
No full textA review of the book: Donald R Rothwell and Tim Stephens, The International Law of the Sea (London: Bloomsbury, 2016, 2nd ed.), pp. 553 & xlviii, 36 GBP (paperback); 25.99 GBP (kindle ebook), ISBN: 9781782256849 (paperback)
R.A. Taylor photograph, Rothwell Fair, 1989.
No full textPhotograph of William Thurston's Seddon Atkinson - YHV441T - Orbiter load, taken Rothwell, May 1989
R.A. Taylor photograph, Rothwell Fair, 1991.
No full textPhotograph of William Thurston Junior's ERF with Zipper load, taken Market Hill, Rothwell, May 1991
Depression of Renshaw recurrent inhibition by activation of corticospinal fibres in human upper and lower limb.
No full text1. This study tested whether the recurrent inhibition of soleus and wrist flexor motoneurones could be modified by transcranial magnetic stimulation in human subjects. 2. Magnetic stimulation was given through a circular coil centred at the vertex. The intensity of the magnetic stimulus was subthreshold for evoking a motor response in the active soleus and wrist flexor muscles. The recurrent inhibition brought about by a conditioning H1 reflex discharge was estimated by a test H' reflex. The modifications of the recurrent inhibition after cortical stimulation were distinguished from the motoneuronal changes by comparing H' to a reference H reflex. 3. In the soleus motoneurones, the reference H reflex was inhibited at a minimum conditioning‐test interval of ‐2 ms (H reflex stimulus before magnetic stimulation). In contrast, the H' reflex was facilitated at minimum conditioning‐test intervals of +1 ms. In the wrist flexor motoneurones, both H' and reference H reflexes were facilitated. However, at lower cortical stimulus intensities, only the H' reflex was facilitated at minimum conditioning‐test intervals of +1 ms. 4. In both motoneurone pools, H' facilitation started 3‐4 ms later than the earliest changes in the reference H reflex. Also, the threshold of H' facilitation was lower than that of reference H reflex. 5. It is concluded that facilitation of the H' reflex is produced by corticospinal inhibition of Renshaw cells via a short interneuronal chain in both the upper and lower limb
Distribution of Ia effects onto human hand muscle motoneurones as revealed using an H reflex technique.
No full text1. The possibility of eliciting H reflexes in relaxed hand muscles using a collision between the orthodromic impulses generated by magnetic cortical stimulation and the antidromic motor volley due to a supramaximal (SM) peripheral nerve stimulus was investigated in seven subjects. 2. Magnetic stimuli, applied through a circular coil (outer diameter, 13 cm) centred at the vertex, evoking EMG responses of 3-5 mV amplitude in the relaxed abductor digit minimi (ADM) muscle, and SM test stimuli to the ulnar nerve at the wrist producing a direct maximal motor response (Mmax) in the ADM muscle, were given either alone or combined. 3. In all subjects, combined cortical and SM ulnar stimulation produced a response after the Mmax with the latency of an H reflex evoked by the ulnar stimulus. This response occurred only within interstimulus intervals (1-20 ms) compatible with collision in the motor axons. The response behaved like an H reflex being time-locked to the SM ulnar stimulus, facilitated by voluntary activation of ADM muscle, depressed by vibration (4 s, 100 Hz) of ADM tendon and by a submotor-threshold ulnar nerve stimulus applied 50 and 80 ms before the combined stimulation, respectively. 4. In some subjects, it was also possible to distinguish an earlier response preceding the H reflex by 3 ms. Evidence is given that this response is probably of cortical origin. 5. Varying the intensity of magnetic stimulation resulted in a non-linear relationship between the H reflex size and the size of the cortical response. When the latter was between 5-25% of Mmax, H reflexes were small (2.5-7.5% of Mmax); with cortical responses between 25-50% of Mmax, there was a steep increase in H reflex amplitude (10-30% of Mmax). We suggest that this behaviour is due to an uneven distribution of Ia effects within the motoneurone pool
Anemia quatsinoensis sp nov (Schizaeaceae), a permineralized fern from the lower Cretaceous of Vancouver Island.
No full textAnatomically preserved schizaeaceous vegetative and fertile organs have been identified from the Apple Bay locality (Lower Cretaceous) of Vancouver Island, British Columbia. Specimens are permineralized in calcareous nodules that contain numerous plants and marine invertebrates. Fertile pinnules are pinnately lobed, with abaxial sporangia and abaxially reflexed laminae. The pyriform sporangia have an apical annulus and occur in two rows on each pinnule lobe. Laminar tissue has wavy, thick-walled, adaxial epidermal cells. Spores are tetrahedral to globose with three sets of obliquely arranged parallel muri and correspond to the sporae dispersae genus Cicatricosisporites Potonie´ et Gelletich. This fertile material most closely resembles Anemia subgenus Anemiorrhiza (Schizaeaceae) and is described as a new species, Anemia quatsinoensis Hernandez-Castillo, Stockey et Rothwell. Fertile pinnae are associated with an exarch, amphiphloic, solenostelic Anemia-like rhizome, with a C-shaped frond trace. Anatomies of the solenostele and frond trace, as well as frond divergence, compare most closely with species of Anemia subgenus Anemiorrhiza and may represent the vegetative shoot of Anemia quatsinoensis. This is the oldest and most complete permineralized fertile material of the genus Anemia in North America, and its presence at Apple Bay is consistent with the hypothesis that much of the diversification of Schizaeaceae had already occurred by the beginning of the Cretaceous
High frequency somatosensory stimulation in dystonia: Evidence for defective inhibitory plasticity
No full textBackground: Apart from motor symptoms, multiple deficits of sensory processing have been demonstrated in dystonia. The most consistent behavioural measure of this is abnormal somatosensory temporal discrimination threshold, which has recently been associated with physiological measures of reduced inhibition within the primary somatosensory area. High-frequency repetitive sensory stimulation is a patterned electric stimulation applied to the skin through surface electrodes that has been recently reported to shorten somatosensory temporal discrimination in healthy subjects and to increase the resting level of excitability in several different types of inhibitory interaction in the somatosensory and even motor areas.
Objectives: We tested whether high-frequency repetitive sensory stimulation could augment cortical inhibition and, in turn, ameliorate somatosensory temporal discrimination in cervical dystonia.
Methods: Somatosensory temporal discrimination and a number of electrophysiological measures of sensorimotor inhibition and facilitation were measured before and after 45 minutes of high-frequency repetitive sensory stimulation.
Results: As compared with a group of healthy volunteers of similar age, in whom high-frequency repetitive sensory stimulation increased inhibition and shortened somatosensory temporal discrimination, patients with cervical dystonia showed a consistent, paradoxical response: they had reduced suppression of paired-pulse somatosensory evoked potentials, as well as reduced high-frequency oscillations, lateral inhibition, and short interval intracortical inhibition. Somatosensory temporal discrimination deteriorated after the stimulation protocol, and correlated with reduced measures of inhibition within the primary somatosensory cortex.
Conclusions: We suggest that patients with dystonia have abnormal homeostatic inhibitory plasticity within the sensorimotor cortex and that this is responsible for their paradoxical response to high-frequency repetitive sensory stimulation
Micro-XRF studies of sediment cores: A perspective on capability and application in the environmental sciences
No full textControllable pulse parameter TMS and TMS-EEG as novel approaches to improve neural targeting with rTMS in human cerebral cortex
No full textRepetitive transcranial magnetic stimulation (rTMS) can produce after-effects on the excitability and function of the stimulated cortical site that outlasts the period of stimulation for several minutes or hours (Hamada et al., 2008; Huang et al., 2005; Ridding and Ziemann, 2010; Sommer et al., 2013). These are thought to involve early phases of long term potentiation/depression at cortical synapses. Depending on the area stimulated, the after-effects can influence performance of a variety of cognitive and motor tasks, as well as learning (Parkin et al., 2015; Censor and Cohen, 2011). Reports of beneficial effects on behaviour in healthy populations have led to widespread interest in applying rTMS therapeutically, for example in patients with neuropsychiatric and neurological disorders (George et al., 2013; Lefaucheur et al., 2014; Ridding and Rothwell, 2007).
A major issue with rTMS protocols is that the effects vary considerably within and between individuals (Hamada et al., 2013; Lopez-Alonso et al., 2014; Simeoni et al., 2016; Hinder et al., 2014; Vallence et al., 2015; Vernet et al., 2013; Goldsworthy et al., 2014; Maeda et al., 2000), which causes problems in replication of results in a research setting (Heroux et al., 2015), and is an obstacle to using rTMS in a therapeutic setting. A separate, but related, issue is that rTMS over a given cortical area is often assumed to affect all neuronal populations equally and thus affect all behaviours involving that area similarly, but this may not be true. Here we argue that advanced technologies and methodologies, such as controllable pulse parameter TMS (cTMS; (Peterchev et al., 2014)) and combining TMS with electroencephalography (EEG) (Ilmoniemi and Kicic, 2010; Peterchev et al., 2014), might facilitate the development of more selective forms of stimulation targeting particular neuronal populations or brain states, and ultimately improve the reliability and behavioural specificity of rTMS protocols
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