2,315 research outputs found
Muscle Fatigue Analysis Using OpenSim
In this research, attempts are made to conduct concrete muscle fatigue
analysis of arbitrary motions on OpenSim, a digital human modeling platform. A
plug-in is written on the base of a muscle fatigue model, which makes it
possible to calculate the decline of force-output capability of each muscle
along time. The plug-in is tested on a three-dimensional, 29 degree-of-freedom
human model. Motion data is obtained by motion capturing during an arbitrary
running at a speed of 3.96 m/s. Ten muscles are selected for concrete analysis.
As a result, the force-output capability of these muscles reduced to 60%-70%
after 10 minutes' running, on a general basis. Erector spinae, which loses
39.2% of its maximal capability, is found to be more fatigue-exposed than the
others. The influence of subject attributes (fatigability) is evaluated and
discussed
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Epigenetic memory in induced pluripotent stem cells.
Somatic cell nuclear transfer and transcription-factor-based reprogramming revert adult cells to an embryonic state, and yield pluripotent stem cells that can generate all tissues. Through different mechanisms and kinetics, these two reprogramming methods reset genomic methylation, an epigenetic modification of DNA that influences gene expression, leading us to hypothesize that the resulting pluripotent stem cells might have different properties. Here we observe that low-passage induced pluripotent stem cells (iPSCs) derived by factor-based reprogramming of adult murine tissues harbour residual DNA methylation signatures characteristic of their somatic tissue of origin, which favours their differentiation along lineages related to the donor cell, while restricting alternative cell fates. Such an 'epigenetic memory' of the donor tissue could be reset by differentiation and serial reprogramming, or by treatment of iPSCs with chromatin-modifying drugs. In contrast, the differentiation and methylation of nuclear-transfer-derived pluripotent stem cells were more similar to classical embryonic stem cells than were iPSCs. Our data indicate that nuclear transfer is more effective at establishing the ground state of pluripotency than factor-based reprogramming, which can leave an epigenetic memory of the tissue of origin that may influence efforts at directed differentiation for applications in disease modelling or treatment
Relationship between cloud condensation nuclei (CCN) concentration and aerosol optical depth in the Arctic region
To determine the direct and indirect effects of aerosols on climate, it is important to know the spatial and temporal variations in cloud condensation nuclei (CCN) concentrations. Although many types of CCN measurements are available, extensive CCN measurements are challenging because of the complexity and high operating cost, especially in remote areas. As aerosol optical depth (AOD) can be readily observed by remote sensing, many attempts have been made to estimate CCN concentrations from AOD. In this study, the CCN–AOD relationship is parameterized based on CCN ground measurements from the Zeppelin Observatory (78.91° N, 11.89° E, 474 m asl) in the Arctic region. The AOD measurements were obtained from the Ny-Ålesund site (78.923° N, 11.928° E) and Modern-Era Retrospective Analysis for Research and Applications, Version 2 reanalysis. Our results show a CCN–AOD correlation with a coefficient of determination R2 of 0.59. Three additional estimation models for CCN were presented based on the following data: (i) in situ aerosol chemical composition, (ii) in situ aerosol optical properties, and (iii) chemical composition of AOD obtained from reanalysis data. The results from the model using in situ aerosol optical properties reproduced the observed CCN concentration most efficiently, suggesting that the contribution of BC to CCN concentration should be considered along with that of sulfate
Differences in Disease Severity but Similar Telomere Lengths in Genetic Subgroups of Patients with Telomerase and Shelterin Mutations
This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Supernova Remnants as Clues to Their Progenitors
Supernovae shape the interstellar medium, chemically enrich their host
galaxies, and generate powerful interstellar shocks that drive future
generations of star formation. The shock produced by a supernova event acts as
a type of time machine, probing the mass loss history of the progenitor system
back to ages of 10 000 years before the explosion, whereas supernova
remnants probe a much earlier stage of stellar evolution, interacting with
material expelled during the progenitor's much earlier evolution. In this
chapter we will review how observations of supernova remnants allow us to infer
fundamental properties of the progenitor system. We will provide detailed
examples of how bulk characteristics of a remnant, such as its chemical
composition and dynamics, allow us to infer properties of the progenitor
evolution. In the latter half of this chapter, we will show how this exercise
may be extended from individual objects to SNR as classes of objects, and how
there are clear bifurcations in the dynamics and spectral characteristics of
core collapse and thermonuclear supernova remnants. We will finish the chapter
by touching on recent advances in the modeling of massive stars, and the
implications for observable properties of supernovae and their remnants.Comment: A chapter in "Handbook of Supernovae" edited by Athem W. Alsabti and
Paul Murdin (18 pages, 6 figures
Prevalence of primary headaches in Germany: results of the German Headache Consortium Study
We investigated the prevalence of migraine (MIG), tension-type headache (TTH), and chronic headache in a population-based sample in Germany. A total of 18,000 subjects aged between 18 and 65 years were screened from 2003 until 2005 using a validated questionnaire. Overall 9,944 participants (55.2%) responded (mean age 43 ± 13.1 years, 52.7% women). Headache frequency <15 days/month was reported by 5,350 (55.5%) subjects of whom 1,601 (16.6%, [95% confidence interval (95% CI): 15.9–17.4]) reported episodic MIG, 1,202 (12.5%, 95% CI 11.8–13.1) episodic TTH, and 1,150 (11.9%, [11.3–12.6]) episodic MIG + episodic TTH, 1,396 (14.5%, [13.8–15.2]) unclassifiable headache. In women, episodic MIG peaked between 36 and 40 years, episodic MIG + TTH between 18 and 35 years and episodic TTH between 56 and 66 years. In men, episodic MIG was predominant between 36 and 45 years, episodic MIG + TTH between 26 and 35 years and episodic TTH showed comparable frequency between 36 and 66 years. Headache ≥15 days/month was reported by 2.6% (n = 255, [95% CI 2.3–3]). Chronic MIG was reported by 1.1% (n = 108, [0.91–1.33]), chronic TTH (n = 50, [95% CI 0.4–0.7]), chronic MIG + TTH 0.8% (n = 74, 95% CI 0.6–0.9) and unclassifiable headache 0.2% (n = 23, [95% CI 0.1–0.3]). Chronic headache was more frequent in women compared to men with the highest prevalence between 46 and 65 years. It is of note that the number of subjects with chronic headache is small in all age groups. The results of our large, population-based study provide reliable, age- and sex-specific estimates of the prevalence of primary headache disorders in Germany. The prevalence with respect to episodic and chronic primary headache disorders in Germany is comparable to other European countries and the USA
Dengue virus neutralizing antibody levels associated with protection from infection in Thai cluster studies
BACKGROUND: Long-term homologous and temporary heterologous protection from dengue virus (DENV) infection may be mediated by neutralizing antibodies. However, neutralizing antibody titers (NTs) have not been clearly associated with protection from infection.
METHODOLOGY/PRINCIPAL FINDINGS: Data from two geographic cluster studies conducted in Kamphaeng Phet, Thailand were used for this analysis. In the first study (2004-2007), cluster investigations of 100-meter radius were triggered by DENV-infected index cases from a concurrent prospective cohort. Subjects between 6 months and 15 years old were evaluated for DENV infection at days 0 and 15 by DENV PCR and IgM ELISA. In the second study (2009-2012), clusters of 200-meter radius were triggered by DENV-infected index cases admitted to the provincial hospital. Subjects of any age 6 months and older were evaluated for DENV infection at days 0 and 14. In both studies, subjects who were DENV PCR positive at day 14/15 were considered to have been susceptible on day 0. Comparison subjects from houses in which someone had documented DENV infection, but the subject remained DENV negative at days 0 and 14/15, were considered non-susceptible. Day 0 samples were presumed to be from just before virus exposure, and underwent plaque reduction neutralization testing (PRNT). Seventeen susceptible (six DENV-1, five DENV-2, and six DENV-4), and 32 non-susceptible (13 exposed to DENV-1, 10 DENV-2, and 9 DENV-4) subjects were evaluated. Comparing subjects exposed to the same serotype, receiver operating characteristic (ROC) curves identified homotypic PRNT titers of 11, 323 and 16 for DENV-1, -2 and -4, respectively, to differentiate susceptible from non-susceptible subjects.
CONCLUSIONS/SIGNIFICANCE: PRNT titers were associated with protection from infection by DENV-1, -2 and -4. Protective NTs appeared to be serotype-dependent and may be higher for DENV-2 than other serotypes. These findings are relevant for both dengue epidemiology studies and vaccine development efforts
An Integrated-Photonics Optical-Frequency Synthesizer
Integrated-photonics microchips now enable a range of advanced
functionalities for high-coherence applications such as data transmission,
highly optimized physical sensors, and harnessing quantum states, but with
cost, efficiency, and portability much beyond tabletop experiments. Through
high-volume semiconductor processing built around advanced materials there
exists an opportunity for integrated devices to impact applications cutting
across disciplines of basic science and technology. Here we show how to
synthesize the absolute frequency of a lightwave signal, using integrated
photonics to implement lasers, system interconnects, and nonlinear frequency
comb generation. The laser frequency output of our synthesizer is programmed by
a microwave clock across 4 THz near 1550 nm with 1 Hz resolution and
traceability to the SI second. This is accomplished with a heterogeneously
integrated III/V-Si tunable laser, which is guided by dual
dissipative-Kerr-soliton frequency combs fabricated on silicon chips. Through
out-of-loop measurements of the phase-coherent, microwave-to-optical link, we
verify that the fractional-frequency instability of the integrated photonics
synthesizer matches the reference-clock instability for a 1
second acquisition, and constrain any synthesis error to while
stepping the synthesizer across the telecommunication C band. Any application
of an optical frequency source would be enabled by the precision optical
synthesis presented here. Building on the ubiquitous capability in the
microwave domain, our results demonstrate a first path to synthesis with
integrated photonics, leveraging low-cost, low-power, and compact features that
will be critical for its widespread use.Comment: 10 pages, 6 figure
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