4,040 research outputs found
The Stability of Orthotropic Elliptic Cylinders in Pure Bending
The theoretical critical bending stress of elliptic cylindrical shells is determined on the assumption of infinite shell length and absence of local instability phenomena. The results of the tests on isotropic elliptic cylindrical shells stressed in bending are compared with the theoretical results. The practical applicability of the theory is discussed
Methods and formulas for calculating the strength of plate and shell constructions as used in airplane design
This report is a compilation of previously published articles on formulas and methods of calculation for the determination of the strength and stability of plate and shell construction as employed in airplane design. In particular, it treats the problem of isotropic, orthotopic, and stiffened rectangular plates, thin curved panels, and circular cylinders under various loading conditions. The purpose of appending the pertinent literature references following the subjects discussed was to facilitate a comprehensive study of the treated problems
Understanding of Relation Structures of Graphical Models by Lower Secondary Students
A learning path has been developed on system dynamical graphical modelling, integrated into the Dutch lower secondary physics curriculum. As part of the developmental research for this learning path, students’ understanding of the relation structures shown in the diagrams of graphical system dynamics based models has been investigated. One of our main findings is that only some students understand these structures correctly. Reality-based interpretation of the diagrams can conceal an incorrect understanding of diagram structures. As a result, students seemingly have no problems interpreting the diagrams until they are asked to construct a graphical model. Misconceptions have been identified that are the consequence of the fact that the equations are not clearly communicated by the diagrams or because the icons used in the diagrams mislead novice modellers. Suggestions are made for improvements
Presolar Grains from Novae: Evidence from Neon and Helium Isotopes in Comet Dust Collections
Presolar grains in meteorites and interplanetary dust particles (IDPs) carry
non-solar isotopic signatures pointing to origins in supernovae, giant stars,
and possibly other stellar sources. There have been suggestions that some of
these grains condensed in the ejecta of classical nova outbursts, but the
evidence is ambiguous. We report neon and helium compositions in particles
captured on stratospheric collectors flown to sample materials from comets
26P/Grigg-Skjellerup and 55P/Tempel-Tuttle that point to condensation of their
gas carriers in the ejecta of a neon (ONe) nova. The absence of detectable 3He
in these particles indicates space exposure to solar wind (SW) irradiation of a
few decades at most, consistent with origins in cometary dust streams. Measured
4He/20Ne, 20Ne/22Ne, 21Ne/22Ne and 20Ne/21Ne isotope ratios, and a low upper
limit on 3He/4He, are in accord with calculations of nucleosynthesis in neon
nova outbursts. Of these, the uniquely low 4He/20Ne and high 20Ne/22Ne ratios
are the most diagnostic, reflecting the large predicted 20Ne abundances in the
ejecta of such novae. The correspondence of measured Ne and He compositions in
cometary matter with theoretical predictions is evidence for the presence of
presolar grains from novae in the early solar system.Comment: As appeared in the Astrophysical Journa
New attempts to understand nanodiamond stardust
We report on a concerted effort aimed at understanding the origin and history
of the pre-solar nanodiamonds in meteorites including the astrophysical sources
of the observed isotopic abundance signatures. This includes measurement of
light elements by secondary ion mass spectrometry (SIMS), analysis of
additional heavy trace elements by accelerator mass spectrometry (AMS) and
dynamic calculations of r-process nucleosynthesis with updated nuclear
properties. Results obtained indicate: a) there is no evidence for the former
presence of now extinct 26Al and 44Ti in our diamond samples other than what
can be attributed to silicon carbide and other "impurities"; this does not
offer support for a supernova (SN) origin but neither does it negate it; b)
analysis by AMS of platinum in "bulk diamond" yields an overabundance of r-only
198Pt that at face value seems more consistent with the neutron burst than with
the separation model for the origin of heavy trace elements in the diamonds,
although this conclusion is not firm given analytical uncertainties; c) if the
Xe-H pattern was established by an unadulterated r-process, it must have been a
strong variant of the main r-process, which possibly could also account for the
new observations in platinum.Comment: Workshop on Astronomy with Radioactvities VII; Publications of the
Astronomical Society of Australia, accepte
Doxorubicin-induced DNA Damage Causes Extensive Ubiquitination of Ribosomal Proteins Associated with a Decrease in Protein Translation
Protein posttranslational modifications (PTMs) play a central role in the DNA damage response. In particular, protein phosphorylation and ubiquitination have been shown to be essential in the signaling cascade that coordinates break repair with cell cycle progression. Here, we performed whole-cell quantitative proteomics to identify global changes in protein ubiquitination that are induced by DNA double-strand breaks. In total, we quantified more than 9,400 ubiquitin sites and found that the relative abundance of similar to 10% of these sites was altered in response to DNA double-strand breaks. Interestingly, a large proportion of ribosomal proteins, including those from the 40S as well as the 60S subunit, were ubiquitinated in response to DNA damage. In parallel, we discovered that DNA damage leads to the inhibition of ribosome function. Taken together, these data uncover the ribosome as a major target of the DNA damage response.This work is funded by a TOP-GO grant from the Netherlands Organization for Scientific Research (NWO ZonMW 912100651 to R.H.M., S.M., and V.A.H.). I.G.S. was supported with a postdoctoral fellowship from the Basque Country Government (Spain). We thank Christian Frese and Teck Yew Low for fruitful discussions. We also thank Teck Yew Low for submitting the raw files and annotated spectra to PRIDE. We thank Fabricio Loayza-Puch for his technical help with the sucrose gradients
Vacuum stability and the Cholesky decomposition
We discuss how the Cholesky decomposition may be used to ascertain whether a
critical point of the field theory scalar potential provides a stable vacuum
configuration. We then use this method to derive the stability conditions in a
specific example.Comment: 7 page
Suppressed Charge Dispersion via Resonant Tunneling in a Single-Channel Transmon
We demonstrate strong suppression of charge dispersion in a
semiconductor-based transmon qubit across Josephson resonances associated with
a quantum dot in the junction. On resonance, dispersion is drastically reduced
compared to conventional transmons with corresponding Josephson and charging
energies. We develop a model of qubit dispersion for a single-channel
resonance, which is in quantitative agreement with experimental data
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