2,741 research outputs found
Plasmon Evolution and Charge-Density Wave Suppression in Potassium Intercalated Tantalum Diselenide
We have investigated the influence of potassium intercalation on the
formation of the charge-density wave (CDW) instability in 2H-tantalum
diselenide by means of Electron Energy-Loss Spectroscopy and density functional
theory. Our observations are consistent with a filling of the conduction band
as indicated by a substantial decrease of the plasma frequency in experiment
and theory. In addition, elastic scattering clearly points to a destruction of
the CDW upon intercalation as can be seen by a vanishing of the corresponding
superstructures. This is accompanied by a new superstructure, which can be
attributed to the intercalated potassium. Based on the behavior of the c-axis
upon intercalation we argue in favor of interlayer-sites for the alkali-metal
and that the lattice remains in the 2H-modification
Cost-utility analyses in orthopaedic surgery
BACKGROUND: The rising cost of health care has increased the need for the orthopaedic community to understand and apply economic evaluations. We critically reviewed the literature on orthopaedic cost-utility analysis to determine which subspecialty areas are represented, the cost-utility ratios that have been utilized, and the quality of the present literature.
METHODS: We searched the English-language medical literature published between 1976 and 2001 for orthopaedic-related cost-utility analyses in which outcomes were reported as cost per quality-adjusted life year. Two trained reviewers independently audited each article to abstract data on the methods and reporting practices used in the study as well as the cost-utility ratios derived by the analysis.
RESULTS: Our search yielded thirty-seven studies, in which 116 cost-utility ratios were presented. Eleven of the studies were investigations of treatment strategies in total joint arthroplasty. Study methods varied substantially, with only five studies (14%) including four key criteria recommended by the United States Panel on Cost-Effectiveness in Health and Medicine. According to a reader-assigned measure of study quality, cost-utility analyses in orthopaedics were of lower quality than those in other areas of medicine (p = 0.04). While the number of orthopaedic studies has increased in the last decade, the quality did not improve over time and did not differ according to subspecialty area or journal type. For the majority of the interventions that were studied, the cost-utility ratio was below the commonly used threshold of $50,000 per quality-adjusted life year for acceptable cost-effectiveness.
CONCLUSIONS: Because of limitations in methodology, the current body of literature on orthopaedic cost-utility analyses has a limited ability to guide policy, but it can be useful for setting priorities and guiding research. Future research with clear and transparent reporting is needed in all subspecialty areas of orthopaedic practice
Functional brain plasticity during L1 training on complex sentences: Changes in gammaâband oscillatory activity
The adult human brain remains plastic even after puberty. However, whether first language (L1) training in adults can alter the language network is yet largely unknown. Thus, we conducted a longitudinal training experiment on syntactically complex German sentence comprehension. Sentence complexity was varied by the depth of the center embedded relative clauses (i.e., single or double embedded). Comprehension was tested after each sentence with a question on the thematic role assignment. Thirty adult, native German speakers were recruited for 4âdays of training. Magnetoencephalography (MEG) data were recorded and subjected to spectral power analysis covering the classical frequency bands (i.e., theta, alpha, beta, low gamma, and gamma). Normalized spectral power, time-locked to the final closure of the relative clause, was subjected to a two-factor analysis (âsentence complexityâ and âtraining daysâ). Results showed that for the more complex sentences, the interaction of sentence complexity and training days was observed in Brodmann area 44 (BA 44) as a decrease of gamma power with training. Moreover, in the gamma band (55â95âHz) functional connectivity between BA 44 and other brain regions such as the inferior frontal sulcus and the inferior parietal cortex were correlated with behavioral performance increase due to training. These results show that even for native speakers, complex L1 sentence training improves language performance and alters neural activities of the left hemispheric language network. Training strengthens the use of the dorsal processing stream with working-memory-related brain regions for syntactically complex sentences, thereby demonstrating the brain's functional plasticity for L1 training
Global existence and asymptotic behaviour in the future for the Einstein-Vlasov system with positive cosmological constant
The behaviour of expanding cosmological models with collisionless matter and
a positive cosmological constant is analysed. It is shown that under the
assumption of plane or hyperbolic symmetry the area radius goes to infinity,
the spacetimes are future geodesically complete, and the expansion becomes
isotropic and exponential at late times. This proves a form of the cosmic no
hair theorem in this class of spacetimes
Stable oxygen and carbon isotopes of carbonates in lake sediments as a paleoflood proxy
Lake sediments are increasingly explored as reliable paleoflood archives. In addition to
established flood proxies including detrital layer thickness, chemical composition, and grain
size, we explore stable oxygen and carbon isotope data as paleoflood proxies for lakes in
catchments with carbonate bedrock geology. In a case study from Lake Mondsee (Austria),
we integrate high-resolution sediment trapping at a proximal and a distal location and stable
isotope analyses of varved lake sediments to investigate flood-triggered detrital sediment flux.
First, we demonstrate a relation between runoff, detrital sediment flux, and isotope values in
the sediment trap record covering the period 2011â2013 CE including 22 events with daily
(hourly) peak runoff ranging from 10 (24) m3 sâ1 to 79 (110) m3 sâ1. The three- to ten-fold
lower flood-triggered detrital sediment deposition in the distal trap is well reflected by attenuated
peaks in the stable isotope values of trapped sediments. Next, we show that all nine
flood-triggered detrital layers deposited in a sediment record from 1988 to 2013 have elevated
isotope values compared with endogenic calcite. In addition, even two runoff events that did
not cause the deposition of visible detrital layers are distinguished by higher isotope values.
Empirical thresholds in the isotope data allow estimation of magnitudes of the majority of
floods, although in some cases flood magnitudes are overestimated because local effects can
result in too-high isotope values. Hence we present a proof of concept for stable isotopes as
reliable tool for reconstructing flood frequency and, although with some limitations, even
for flood magnitudes
Cell proliferation and differentiation kinetics during spermatogenesis in Hydra carnea
Spermatogenesis inHydra carnea was investigated. The cell proliferation and differentiation kinetics of intermediates in the spermatogenesis pathway were determined, using quantitative determinations of cell abundance, pulse and continuous labelling with3H-thymidine and nuclear DNA measurements. Testes develop in the ectoderm of male hydra as a result of interstitial cell proliferation. Gonial stem cells and proliferating spermatogonia have cell cycles of 28 h and 22 h, respectively. Stem cells undergo four, five or six cell divisions prior to meiosis which includes a premeiotic S+G2 phase of 20 h followed by a long meiotic prophase (22 h).
Spermatid differentiation requires 12â29 h. When they first appear, testes contain only proliferating spermatogonia; meiotic and postmeiotic cells appear after 2 and 3 days, respectively and release of mature sperm begins after 4 days. Mature testes produce about 27,000 sperm per day over a period of 4â6 days: about 220 gonial stem cells per testis are required to support this level of sperm differentiation. Further results indicate that somatic (e.g. nematocyte) differentiation does not occur in testes although it continues normally in ectodermal tissue outside testes. Our results support the hypothesis that spermatogenesis is controlled locally in regions of the ectoderm where testes develop
Validation of Kalman Filter alignment algorithm with cosmic-ray data using a CMS silicon strip tracker endcap
A Kalman Filter alignment algorithm has been applied to cosmic-ray data. We
discuss the alignment algorithm and an experiment-independent implementation
including outlier rejection and treatment of weakly determined parameters.
Using this implementation, the algorithm has been applied to data recorded with
one CMS silicon tracker endcap. Results are compared to both photogrammetry
measurements and data obtained from a dedicated hardware alignment system, and
good agreement is observed.Comment: 11 pages, 8 figures. CMS NOTE-2010/00
Individual alpha power predicts language comprehension
Alpha power attenuation during cognitive task performing has been suggested to reflect a process of release of inhibition, increase of excitability, and thereby benefit the improvement of performance. Here, we hypothesized that changes in individual alpha power during the execution of a complex language comprehension task may correlate with the individual performance in that task. We tested this using magnetoencephalography (MEG) recorded during comprehension of German sentences of different syntactic complexity. Results showed that neither the frequency nor the power of the spontaneous oscillatory activity at rest were associated with the individual performance. However, during the execution of a sentences processing task, the individual alpha power attenuation did correlate with individual language comprehension performance. Source reconstruction localized effects in temporal-parietal regions of both hemispheres. While the effect of increased task difficulty is localized in the right hemisphere, the difference in power attenuation between tasks of different complexity exhibiting a correlation with performance was localized in left temporal-parietal brain regions known to be associated with language processing. From our results, we conclude that in-task attenuation of individual alpha power is related to the essential mechanisms of the underlying cognitive processes, rather than merely to general phenomena like attention or vigilance
Alpha power during task performance predicts individual language comprehension
Alpha power attenuation during cognitive task performing has been suggested to reflect a process of release of inhibition, increase of excitability, and thereby benefit the improvement of performance. Here, we hypothesized that changes in individual alpha power during the execution of a complex language comprehension task may correlate with the individual performance in that task. We tested this using magnetoencephalography (MEG) recorded during comprehension of German sentences of different syntactic complexity. Results showed that neither the frequency nor the power of the spontaneous oscillatory activity at rest were associated with the individual performance. However, during the execution of a sentences processing task, the individual alpha power attenuation did correlate with individual language comprehension performance. Source reconstruction localized effects in temporal-parietal regions of both hemispheres. While the effect of increased task difficulty is localized in both hemispheres, the difference in power attenuation between tasks of different complexity exhibiting a correlation with performance was localized in left temporal-parietal brain regions known to be associated with language processing. Our results support the notion that in-task attenuation of individual alpha power is related to the essential mechanisms of the underlying cognitive processes, rather than merely to general phenomena like attention or vigilance
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