7,996 research outputs found
Intercellular communication in normal and regenerating rat liver: a quantitative analysis
We have compared intercellular communication in the regenerating and normal livers of weanling rats. The electrophysiological studies were conducted at the edge of the liver, and we have found that here as elsewhere in the liver there is a dramatic decrease in the number and size of gap junctions during regeneration. The area of hepatocyte membrane occupied by gap junctions is reduced 100-fold 29-35 h after hepatectomy. By combining observations made with the scanning electron microscope with our freeze fracture data we have estimated the number of "communicating interfaces" (areas of contact between hepatocytes that include at least one gap junction) formed by hepatocytes in normal and regenerating liver. In normal liver a hepatocyte forms gap junctions with every hepatocyte it contacts (approximately 6). In regenerating liver a hepatocyte forms detectable gap junctions with, on average, only one other hepatocyte. Intercellular spread of fluorescent dye and electric current is reduced in regenerating as compared with normal liver. The incidence of electric coupling is reduced from 100% of hepatocyte pairs tested in control liver to 92% in regenerating liver. Analysis of the spatial dependence of electronic potentials indicates a substantial increase in intercellular resistance in regenerating liver. A quantitative comparison of our morphological and physiological data is complicated by tortuous pattern of current flow and by inhomogeneities in the liver during regeneration. Nevertheless we believe that our results are consistent with the hypothesis that gap junctions are aggregates of channels between cell interiors
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Towards a New Model of Phonological Encoding
The sound-form generation of a word in speech production involves the retrieval of segmental and suprasegmental information from the mental lexicon. A translation task experiment showed that the naming latencies of target items can be reduced when prime words are presented that have the same placement of the lexical stress as the target. However, this reduction will only occur when primes and targets have the same word onset. A second experiment showed that primes that have the same number of segments as the targets will cause naming facilitation compared to primes that have different numbers of segments. I have developed a new model of phonological encoding that incoqwrates ordered selection of the various elements. Lexical stress is chosen fu-st, followed by information about the number of slots, the word onset, the second segment, and the other segments, until all segments have been selected. The model further employs mechanisms that allow for the retrieval of the initial segment to influence the retrieval of lexical stress. Various simulations show that the model can replicate the findings of the two experiments. Other models of phonological encoding largely neglect suprasegmental retrieval and cannot explain these results
Static Rouse Modes and Related Quantities: Corrections to Chain Ideality in Polymer Melts
Following the Flory ideality hypothesis intrachain and interchain excluded
volume interactions are supposed to compensate each other in dense polymer
systems. Multi-chain effects should thus be neglected and polymer conformations
may be understood from simple phantom chain models. Here we provide evidence
against this phantom chain, mean-field picture. We analyze numerically and
theoretically the static correlation function of the Rouse modes. Our numerical
results are obtained from computer simulations of two coarse-grained polymer
models for which the strength of the monomer repulsion can be varied, from full
excluded volume (`hard monomers') to no excluded volume (`phantom chains'). For
nonvanishing excluded volume we find the simulated correlation function of the
Rouse modes to deviate markedly from the predictions of phantom chain models.
This demonstrates that there are nonnegligible correlations along the chains in
a melt. These correlations can be taken into account by perturbation theory.
Our simulation results are in good agreement with these new theoretical
predictions.Comment: 9 pages, 7 figures, accepted for publication in EPJ
Residual stress of as-deposited and rolled Wire + Arc Additive Manufacturing Ti–6Al–4V components
Wire + arc additive manufacturing components contain significant residual stresses, which manifest in distortion. High-pressure rolling was applied to each layer of a linear Ti–6Al–4V wire + arc additive manufacturing component in between deposition passes. In rolled specimens, out-of-plane distortion was more than halved; a change in the deposits' geometry due to plastic deformation was observed and process repeatability was increased. The Contour method of residual stresses measurements showed that although the specimens still exhibited tensile stresses (up to 500 MPa), their magnitude was reduced by 60%, particularly at the interface between deposit and substrate. The results were validated with neutron diffraction measurements, which were in good agreement away from the baseplate
Phase i study of \u27dose-dense\u27 pemetrexed plus carboplatin/radiotherapy for locally advanced non-small cell lung carcinoma.
BACKGROUND: This phase I study investigates the feasibility of carboplatin plus dose-dense (q2-week) pemetrexed given concurrently with radiotherapy (XRT) for locally advanced and oligometastatic non-small cell lung cancer (NSCLC).
METHODS: Eligible patients had Stage III or IV (oligometastatic) NSCLC. Patients received XRT to 63 Gy in standard fractionation. Patients received concurrent carboplatin (AUC = 6) during weeks 1 and 5 of XRT, and pemetrexed during weeks 1, 3, 5, and 7 of XRT. The starting dose level (level 1) of pemetrexed was 300 mg/m2. Following the finding of dose limiting toxicity (DLT) in dose level 1, an amended dose level (level 1A) continued pemetrexed at 300 mg/m2, but with involved field radiation instead of extended nodal irradiation. Consolidation consisted of carboplatin (AUC = 6) and pemetrexed (500 mg/m2) q3 weeks × 2 -3 cycles.
RESULTS: Eighteen patients were enrolled. Fourteen patients are evaluable for toxicity analysis. Of the initial 6 patients treated on dose level 1, two experienced DLTs (one grade 4 sepsis, one prolonged grade 3 esophagitis). There was one DLT (grade 5 pneumonitis) in the 8 patients treated on dose level 1A. In 16 patients evaluable for response (4 with oligometastatic stage IV disease and 12 with stage III disease), the median follow-up time is 17.8 months. Thirteen of 16 patients had in field local regional response. The actuarial median survival time was 28.6 months in all patients and 34.7 months (estimated) in stage III patients.
CONCLUSIONS: Concurrent carboplatin with dose-dense (q2week) pemetrexed at 300 mg/m2 with involved field XRT is feasible and encouraging in patients with locally advanced and oligometastatic NSCLC
Martial Arts in the Pandemic
This study examines the impact of the Covid-19 pandemic on martial arts training worldwide. A mixed-method online questionnaire consisting of 28 items was used as a survey instrument. 306 martial artists responded. These were mainly from the United Kingdom, the USA, Germany, Italy and Japan. The questionnaire focused on pragmatic adaptations of training volume, training rhythm, training location, training mode (individual or group) and training methods. The survey sought to gain insights into modifications that martial artists made as a result of the Covid-19 pandemic in relation to their training, curriculum, alternative fitness, strength and health activities, as well as training goals. The results suggest that the training restrictions implemented by governments in order to try to combat the pandemic transformed the practice of martial arts on a massive and fundamental scale. Specifically, they led to two seemingly opposing developments: increasing digitisation and an increased focus on the importance of embodiment. The article concludes with a suggestion that these lines of development will mould the post-pandemic landscape of martial arts
NASA MSFC SPoRT: SPoRT Paradigm, Use of LANCE Data, Data Capabilities
No abstract availabl
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