1. Four paraplegic men volunteered for an exercise programme in which their paralysed quadriceps muscles were stimulated by means of computer-regulated electrical impulses applied through external ...electrodes. The first exercise regimen consisted of leg raising against a graded load, and during the second regimen exercise took the form of cycling on a modified bicycle ergometer. Each subject exercised five times weekly for 10 weeks during the first regimen and 32 weeks during the second regimen. 2. Whole-body protein turnover determined by L-1-13Cleucine during feeding remained constant during both exercise regimens, when expressed either in terms of body weight or fat-free mass derived from measurements of total body potassium. 3. Quadriceps muscle protein synthetic rate increased during the study, from 0.0712 to 0.0985%/h (P less than 0.05), as did quadriceps muscle area assessed by computed tomography. 4. Bone mineral content for lumbar vertebrae was normal in all four patients, but for the femoral mid-shaft bone mineral content averaged only 66% of normal for three of the patients. Trabecular bone density in the distal tibia ranged from normal to 2% of normal for the men with the shortest and longest periods of disability, respectively. No changes in bone mineral content or bone density occurred during the exercise period.
On the grammar of pain Halliday, M A K
Functions of language,
01/1998, Letnik:
5, Številka:
1
Journal Article
Recenzirano
The lexicogrammar of every natural language is (among other things) a theory of human experience, a resource whereby experience is transformed into meaning. One of the most challenging areas of human ...experience is that of pain. If we investigate the grammar of pain in modern English, using evidence from a corpus, a short text, and paradigms of typical expressions in everyday speech, we find that pain is categorized in varying ways, as process, quality and thing, and construed as various different kinds of process. This variation constructs pain as a uniquely complex domain of experience, one that cannot be located within any simply defined region of semantic space.
The
r-process only nuclide
247Cm decays to
235U with a characteristic half-life of ∼16 million years.
247Cm is presently extinct, but offers considerable potential as a short-lived
r-process ...chronometer, providing constraints on the time interval between the last
r-process nucleo-synthetic event and the formation of the solar system. The existence of “live”
247Cm in the early solar system should be manifested today as variations in
235U/
238U, provided Cm was chemically fractionated from U when solids formed in the early solar system. Using multiple-collector ICPMS and a high-purity mixed
233U-
236U spike to monitor instrumental mass fractionation, we are able to resolve variations in
235U/
238U at the 1–2 epsilon level (2σ
M; 1 epsilon = 1 part in 10,000) on sample sizes consisting of 20 ng of uranium. Data can be acquired on smaller (<10 ng) samples with ±2–3 epsilon 2σ uncertainties. Uranium isotopic measurements and U, Nd and Sm concentrations were acquired on bulk samples of a suite of carbonaceous chondrites, unequilibrated and equilibrated ordinary chondrites and eucrites, for which conflicting results had previously been obtained. Our results show no well-resolved excursions in
235U/
238U away from the terrestrial value at the ∼2 epsilon level, and constrain the amount of
247Cm-produced excess
235U atoms to less than ∼1 × 10
8 atoms per gram of chondritic meteorite, with respect to terrestrial
235U/
238U. Large (permil- level) anomalies in
235U/
238U could, however, be artificially generated in the ordinary chondrites during laboratory processing. Therefore, U may be more susceptible to isotopic fractionation during chemical processing than previously recognized, and may reconcile some of the highly conflicting ε
235U results reported by previous workers for chondritic meteorites. Our results indicate that a timescale of ∼1–2 × 10
8 years between the last actinide producing
r-process event and the formation of the solar system may not be unreasonable based on the
247Cm-
235U system. However, this conclusion is far from robust at this stage because the only bulk meteorites analysed that display strong Nd/U fractionation are highly metamorphosed chondrites that may have experienced a protracted history of redistribution and re-equilibration. The search for “live”
247Cm in the early solar system can now be extended to early-formed condensates and mineral phases displaying strong Cm-U fractionations.
The silicate fractions of recent pelagic sediments in the central north Pacific Ocean are dominated by eolian dust derived from central Asia. An 11 Myr sedimentary record at ODP Sites 885/886 at ...44.7°N, 168.3°W allows the evaluation of how such dust and its sources have changed in response to late Cenozoic climate and tectonics. The extracted eolian fraction contains variable amounts (>70%) of clay minerals with subordinate quartz and plagioclase. Uniform Nd isotopic compositions (
ϵ
Nd=−8.6 to −10.5) and Sm/Nd ratios (0.170–0.192) for most of the 11 Myr record demonstrate a well-mixed provenance in the basins north of the Tibetan Plateau and the Gobi Desert that was a source of dust long before the oldest preserved Asian loess formed.
ϵ
Nd values of up to −6.5 for samples <2.9 Ma indicate ≤35 wt% admixture of a young, Kamchatka-like volcanic arc component. The coherence of Pb and Nd in the erosional cycle allows us to constrain the Pb isotopic composition of Asian loess devoid of anthropogenic contamination to
206Pb/
204Pb=18.97±0.06,
207Pb/
204Pb=15.67±0.02,
208Pb/
204Pb=39.19±0.11.
87Sr/
86Sr (0.711–0.721) and Rb/Sr ratios (0.39–1.1) vary with dust mineralogy and provide an age indication of ∼250 Ma.
40Ar/
39Ar ages of six dust samples are uniform around 200 Ma and match the K–Ar ages of modern dust deposited on Hawaii. These data reflect the weighted age average of illite formation. Changes from illite≥smectite with significant kaolinite to illite- and chlorite-rich, kaolinite-free assemblages since the late Pliocene document changes in the intensity of chemical weathering in the source region. Such weathering evidently did not disturb the K–Ar systematics, and only induced scatter in the Rb–Sr data. We propose that when smectite forms at the expense of illite, K and Ar are quantitatively lost from what becomes smectite, but are quantitatively retained in adjacent illite layers.
40Ar/
39Ar age data, therefore, are insensitive to smectite formation during chemical weathering but date the diagenetic growth of illite, the major K-bearing phase in the dust. Over the past 12 Myr, the dust flux to the north Pacific increased by more than an order of magnitude, documenting a substantial drying of central Asia. This climatic change, however, did not alter the ultimate source of the dust, and neoformational products of chemical weathering always remained subordinate to assemblages reworked by mechanical erosion in dust deposited in eastern Asia and the Pacific Ocean.
The W isotopic composition of the bulk silicate Earth (BSE) is chondritic within current analytical uncertainties, indicating that terrestrial core formation commenced more than 50 Myr after the ...differentiation of the earliest planetesimals in the solar system. This is consistent with U
Pb data and holds true whether core formation is modelled as a single catastrophic event or as a continuous process that started late, unless accretion was more than about twice as slow as recently estimated. The chondritic W isotopic composition of the BSE provides support for the assumption that the overall lithophile/siderophile refractory element ratio of the Earth is close to chondritic, but requires mixing to remove early heterogeneities introduced by the accretion of any planetesimals already segregated into silicate and metallic portions with distinct W isotopic compositions. The same applies to any later accreted material, such as the putative Moon-forming giant impactor. Many models of terrestrial accretion and core formation involve a core that developed during the first 90% of accretion history, generally considered to correspond to a time span significantly shorter than that permitted by the W isotopic data. These models are difficult to reconcile with the W isotopic data unless the proto-Earth was re-homogenized by a major impactor, or accretion took longer than currently estimated. The W isotopic compositions of early lunar rocks provide the best hope of determining which model of accretion and core formation is correct for the Earth. A conservative assessment of isotopic ages for lunar highlands rocks, combined with the constraints from W isotopic data, indicate that the onset of major terrestrial core segregation, the formation of the Moon and the development of a lunar magma ocean all took place within < 80 Myr at 4.47 ± 0.04 Ga. Certain isotopic ages for lunar rocks would be consistent with a more restricted time window of 4.50 ± 0.01 Ga. Potassium and Cr isotopic data indicate early volatile depletion of the material from which the Earth and Moon formed and constrain models of pre-core Pb isotopic evolution. The various estimates for the Pb isotopic composition of the BSE seem best explained by strong
U/Pb fractionation accompanying terrestrial core formation. Using the 4.47 ± 0.04 Ga age of the core, the second stage Pb isotopic evolution reproduces reasonable estimates for the present day BSE Pb isotopic composition if the second stage
238U
204Pb
(μ) is in the range of 8.9 ± 0.5. The ‘lead paradox’ is entirely predictable from the 4.47 ± 0.04 Ga age of the core. The similarities between the late ages of the Earth's core, the Moon and the degassing of Xe from the terrestrial mantle are consistent with an accretion history which is more protracted than currently modelled. Alternatively, late impacts may have triggered all of these events. If a single late impact is invoked as an explanation, the Moon must have been derived primarily from the silicate portion of the impactor. Otherwise, the Hf-W data may define the age of a core that formed as a result of another impact, shortly prior to that which formed the Moon.
Pattern evoked responses have been recorded in 19 patients with compression of the optic nerve, chiasm or tract, verified at operation. These included 4 patients with orbital tumours, 5 with ...intracranial meningiomas, 2 with craniopharyngiomas and 8 with pituitary tumours. The evoked response was abnormal in all except one of these patients. The pattern of abnormalities in the response, however, differed from that in the earlier series of patients with primary demyelinating disease. The incidence of delayed responses was much lower, and the magnitude of the delays was smaller. Absent responses were particularly characteristic of patients with intracranial meningiomas. Tumours arising in the region of the sella turcica were associated with a high incidence of abnormalities of the waveform of the response, and asymmetry of the field of the occipital evoked potential was especially characteristic of this group. Most, but not all, asymmetric cases were associated with field defects.
New sample preparation and ion‐exchange separation methods as well as instrumental measurement protocols were established for the determination of trace‐level Cd, In, and Te concentrations in ...geological materials by isotope‐dilution mass spectrometry. High precision isotope ratio measurements were performed with a multiple collector inductively coupled plasma‐mass spectrometer (MC‐ICP‐MS). The mass biases incurred for In and Te were corrected by adding and monitoring Pd and Sb standard solutions, respectively. Mass fractionation of Cd was corrected by using the mass fractionation factor calculated from the measurement of a standard solution. The measurement precision was better than 1 % for Cd, In and Te. Detection limits were < 1 ng g‐1 for Cd, < 0.02 ng g‐1 for In and Te. Using these new analytical techniques, the concentrations of Cd, In and Te were determined in six international geological reference materials. Concentrations could be reproduced within 3% for Cd, 4% for In and 10% for Te. Sample heterogeneity and volatility problems might have been the reason for the relatively large differences between Te replicates. Our results displayed excellent reproducibility compared with those of other techniques and agree well with data from previously published recommended values.
Une nouvelle méthode de préparation des échantillons et de séparation sur résine échangeuse d'ion, ainsi que de nouveaux protocoles instrumentaux d'analyse ont été mis au point pour la détermination de très faibles quantités de Cd, In et Te dans des matériaux géologiques par dilution isotopique. La mesure très précise des rapports isotopiques a été réalisée avec un ICP‐MS à multicollection. Le biais de masse pour In et Te a été corrigé en ajoutant des solutions standards de Pd et Sb. Le fractionnement de masse du Cd a été corrigé en utilisant le coefficient de fractionnement calculéà partir de la mesure d'une solution standard. La précision des mesures est inférieure à 1% pour Cd, In et Te. Les limites de détection sont < 1 ng g‐1 pour Cd, < 0.02 ng g‐1 pour In et Te. Avec ces nouvelles techniques analytiques, nous avons mesuré les concentrations en Cd, In et Te dans six matériaux géologiques de référence. La reproductibilité des valeurs est de l'ordre de 3% pour Cd, 4% pour In et 10% pour Te. Des problèmes d'hétérogénéité des échantillons et de volatilité de l'élément pourraient expliquer les différences relativement grandes entre les replicats de Te. Nos résultats présentent une excellente reproductibilité si on les compare avec ceux obtenus par d'autres techniques et sont en parfait accord avec les valeurs recommandées déjà publiées.
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