A collision in 2009 as the origin of the debris trail of asteroid P/2010 A2

The peculiar object P/2010?A2 was discovered in January 2010 and given a cometary designation because of the presence of a trail of material, although there was no central condensation or coma. The appearance of this object, in an asteroidal orbit (small eccentricity and inclination) in the inner main asteroid belt attracted attention as a potential new member of the recently recognized class of main-belt comets. If confirmed, this new object would expand the range in heliocentric distance over which main-belt comets are found. Here we report observations of P/2010?A2 by the Rosetta spacecraft. We conclude that the trail arose from a single event, rather than a period of cometary activity, in agreement with independent results. The trail is made up of relatively large particles of millimetre to centimetre size that remain close to the parent asteroid. The shape of the trail can be explained by an initial impact ejecting large clumps of debris that disintegrated and dispersed almost immediately. We determine that this was an asteroid collision that occurred around 10 February 2009.     

Thinking Through the Prism of Life

The article provides an overview of the argument in Robert Scharff’s paper “Displacing epistemology: Being in the midst of technoscientific practice” (Scharff 2011), focusing on his central objective, to articulate a hidden ground of the current controversies in the philosophy of science and technology studies, between objectivism and constructivism, through a deeper confrontation with Heidegger’s legacy. The commentary addresses two aspects of Scharffs argument that deserve to be developed further, namely how it both criticizes and cultivates itself an ideal of the meta-knower, and how the idea of thinking from the perspective of life in Dilthey’s sense can be critically reflected through Heidegger’s later criticism. By rehearsing Heidegger’s understanding of truth as aletheia, and also his gradually increased criticism of the very concept of life, the commentary tries to show how Scharff’s intervention can in fact be strengthened against possible criticism.     

Gravity modes as a way to distinguish between hydrogen- and helium-burning red giant stars

Red giants are evolved stars that have exhausted the supply of hydrogen in their cores and instead burn hydrogen in a surrounding shell. Once a red giant is sufficiently evolved, the helium in the core also undergoes fusion. Outstanding issues in our understanding of red giants include uncertainties in the amount of mass lost at the surface before helium ignition and the amount of internal mixing from rotation and other processes. Progress is hampered by our inability to distinguish between red giants burning helium in the core and those still only burning hydrogen in a shell. Asteroseismology offers a way forward, being a powerful tool for probing the internal structures of stars using their natural oscillation frequencies. Here we report observations of gravity-mode period spacings in red giants that permit a distinction between evolutionary stages to be made. We use high-precision photometry obtained by the Kepler spacecraft over more than a year to measure oscillations in several hundred red giants. We find many stars whose dipole modes show sequences with approximately regular period spacings. These stars fall into two clear groups, allowing us to distinguish unambiguously between hydrogen-shell-burning stars (period spacing mostly ～ 50 seconds) and those that are also burning helium (period spacing ～ 100 to 300 seconds).     

Ordering and manipulation of the magnetic moments in large-scale superconducting pi-loop arrays

The phase of the macroscopic electron-pair wavefunction in a superconductor can vary only by multiples of 2pi when going around a closed contour. This results in quantization of magnetic flux, one of the most striking demonstrations of quantum phase coherence in superconductors. By using superconductors with unconventional pairing symmetry, or by incorporating pi-Josephson junctions, a phase shift of pi can be introduced in such loops. Under appropriate conditions, this phase shift results in doubly degenerate time-reversed ground states, which are characterized by the spontaneous generation of half quanta of magnetic flux, with magnitude 1/2 Phi(0)(Phi(0) = h/2e = 2.07 x 10(-15) Wb) (ref. 7). Until now, it has only been possible to generate individual half flux quanta. Here we report the realization of large-scale coupled pi-loop arrays based on YBa2Cu3O7-Au-Nb Josephson contacts. Scanning SQUID (superconducting quantum interference device) microscopy has been used to study the ordering of half flux quanta in these structures. The possibility of manipulating the polarities of individual half flux quanta is also demonstrated. These pi-loop arrays are of interest as model systems for studying magnetic phenomena--including frustration effects--in Ising antiferromagnets. Furthermore, studies of coupled pi-loops can be useful for designing quantum computers based on flux-qubits with viable quantum error correction capabilities.     

Abductive Reasoning as a Way of Worldmaking

The author deals with the operational core oflogic, i.e. its diverse procedures ofinference, in order to show that logicallyfalse inferences may in fact be right because –in contrast to logical rationality – theyactually enlarge our knowledge of the world.This does not only mean that logically trueinferences say nothing about the world, butalso that all our inferences are inventedhypotheses the adequacy of which cannot beproved within logic but only pragmatically. Inconclusion the author demonstrates, through therelationship between rule-following andrationality, that it is most irrational to wantto exclude the irrational: it may, at times, bemost rational to think and infer irrationally.Focussing on the operational aspects of knowingas inferring does away with the hiatus betweenlogic and life, cognition and the world(reality) – or whatever other dualism one wantsto invoke –: knowing means inferring, inferringmeans rule-governed interpreting, interpretingis a constructive, synthetic act, and aconstruction that proves adequate (viable) inthe ``world of experience', in life, in thepraxis of living, is, to the constructivistmind, knowledge. It is the practice of livingwhich provides the orienting standards forconstructivist thinking and its judgments ofviability. The question of truth is replaced bythe question of viability, and viabilitydepends on the (right) kind of experiential fit.     

Hydrodynamisches Ähnlichkeitsprinzip zur Bestimmung von Gelstrukturen aus Durchströmungsversuchen

Summary The permeability of jellies of known structure can be determined by experiments on models by application of a principle of hydrodynamical similarity.     

Ein Sensibilisator der therapeutischen Digitaliswirkung

Summary Complexes of bivalent tin with polyoxybenzene-polysulfonic acids have a diuretic effect, when injected subcutaneously in dogs or rabbits. The same compounds also sensibilize the cardiotonic effect of digitalis-substances on the isolated heart or on fragments of the isolated heart as usually employed for testing digitalis-substances.In a small number of patients suffering from heart disease, a rapid increase of their till then lowered diuresis was induced through subcutaneous injections of a solution of the above mentioned tin complex.     

CO2通过安全阀排放流动分析

基于压降经验关联式,对CO2通过安全阀排放流动进行理论研究,分析安全阀的工况和管道结构参数对固体CO2形成的影响.结果表明:当安全阀进出口管径与孔径比为1.1～2.0,安全阀阀杆总上升高度与孔径比为0.1～0.4,下游管径与孔径比为4,下游管长与孔径比为1000时,固体CO2会在安全阀内形成;当安全阀开度大于70%且进出口管径与孔径比小于1.4,或安全阀上游进口压力高于12 MPa时,固体CO2会在下游管路中形成.     

Superoxide anion scavenging effect and superoxide dismutase activity ofGinkgo biloba extract

Summary Ginkgo biloba extract is known to be efficient in diseases associated with free radical generation. The purpose of this work was to study, under in vitro conditions, the action ofGinkgo biloba extract (Gbe) against superoxide anion ( ), which is directly or indirectly implicated in cell damage.Gbe appears to have both an scavenging effect and also a superoxide dismutase activity. Its antiradical effect was demonstrated by low temperature electron spin resonance and in a non-enzymatic system (phenazine methosulfate-NADH), and its enzymatic activity was shown by polarographic determination.     

Reverse breeding in Arabidopsis thaliana generates homozygous parental lines from a heterozygous plant

Traditionally, hybrid seeds are produced by crossing selected inbred lines. Here we provide a proof of concept for reverse breeding, a new approach that simplifies meiosis such that homozygous parental lines can be generated from a vigorous hybrid individual. We silenced DMC1, which encodes the meiotic recombination protein DISRUPTED MEIOTIC cDNA1, in hybrids of A. thaliana, so that non-recombined parental chromosomes segregate during meiosis. We then converted the resulting gametes into adult haploid plants, and subsequently into homozygous diploids, so that each contained half the genome of the original hybrid. From 36 homozygous lines, we selected 3 (out of 6) complementing parental pairs that allowed us to recreate the original hybrid by intercrossing. In addition, this approach resulted in a complete set of chromosome-substitution lines. Our method allows the selection of a single choice offspring from a segregating population and preservation of its heterozygous genotype by generating homozygous founder lines.