Natural frequencies of an orbiting space station

The technique of modal synthesis is applied to find the natural frequencies of space stations. The station is modeled as an assemblage of rigid modules, joined by massless elastic constraints, and flexible modules characterized by deformation functions. The equations of motion are derived and system mass and stiffness matrices derived. The method is applied to the Skylab orbiting space station. The frequencies of the lowest 65 modes are given and selected mode shapes illustrated. The technique is feasible for analysis of a complex system and suitable for response studies including damping and attitude control system effects

Matrix De Rham complex and quantum A-infinity algebras

I establish the relation of the non-commutative BV-formalism with super-invariant matrix integration. In particular, the non-commutative BV-equation, defining the quantum A-infinity-algebras, introduced in "Modular operads and Batalin-Vilkovisky geometry" IMRN, Vol. 2007, doi: 10.1093/imrn/rnm075, is represented via de Rham differential acting on the matrix spaces related with Bernstein-Leites simple associative algebras with odd trace q(N), and with gl(N|N). I also show that the Lagrangians of the matrix integrals from "Noncommmutative Batalin-Vilkovisky geometry and Matrix integrals", Comptes Rendus Mathematique, vol 348 (2010), pp. 359-362, arXiv:0912.5484, are equivariantly closed differential forms.Comment: published versio

Teaching varies with task complexity in wild chimpanzees

Understanding social influences on how apes acquire tool behaviors can help us model the evolution of culture and technology in humans. Humans scaffold novice tool skills with diverse strategies, including the transfer of tools between individuals. Chimpanzees transfer tools, and this behavior meets criteria for teaching. However, it is unclear how task complexity relates to this form of helping. Here, we find differences between 2 wild chimpanzee populations in rate, probability, and types of tool transfer during termite gathering. Chimpanzees showed greater helping in the population where termite gathering is a more complex tool task. In wild chimpanzees, as in humans, regular and active provisioning of learning opportunities may be essential to the cultural transmission of complex skills.Cumulative culture is a transformative force in human evolution, but the social underpinnings of this capacity are debated. Identifying social influences on how chimpanzees acquire tool tasks of differing complexity may help illuminate the evolutionary origins of technology in our own lineage. Humans routinely transfer tools to novices to scaffold their skill development. While tool transfers occur in wild chimpanzees and fulfill criteria for teaching, it is unknown whether this form of helping varies between populations and across tasks. Applying standardized methods, we compared tool transfers during termite gathering by chimpanzees in the Goualougo Triangle, Republic of Congo, and in Gombe, Tanzania. At Goualougo, chimpanzees use multiple, different tool types sequentially, choose specific raw materials, and perform modifications that improve tool efficiency, which could make it challenging for novices to manufacture suitable tools. Termite gathering at Gombe involves a single tool type, fishing probes, which can be manufactured from various materials. Multiple measures indicated population differences in tool-transfer behavior. The rate of transfers and probability of transfer upon request were significantly higher at Goualougo, while resistance to transfers was significantly higher at Gombe. Active transfers of tools in which possessors moved to facilitate possession change upon request occurred only at Goualougo, where they were the most common transfer type. At Gombe, tool requests were typically refused. We suggest that these population differences in tool-transfer behavior may relate to task complexity and that active helping plays an enhanced role in the cultural transmission of complex technology in wild apes

Unstable Hadrons in Hot Hadron Gas in Laboratory and in the Early Universe

We study kinetic master equations for chemical reactions involving the formation and the natural decay of unstable particles in a thermal bath. We consider the decay channel of one into two particles, and the inverse process, fusion of two thermal particles into one. We present the master equations the evolution of the density of the unstable particles in the early Universe. We obtain the thermal invariant reaction rate using as an input the free space (vacuum) decay time and show the medium quantum effects on $\pi+\pi \leftrightarrow \rho$ reaction relaxation time. As another laboratory example we describe the $K+K \leftrightarrow \phi$ process in thermal hadronic gas in heavy-ion collisions. A particularly interesting application of our formalism is the $\pi^{0}\leftrightarrow \gamma +\gamma$ process in the early Universe. We also explore the physics of $\pi^{\pm}$ and $\mu^{\pm}$ freeze-out in the Universe.Comment: 13 pages, 9 figures, published in Physical Review

Efficacy of mupirocin nasal ointment in eradicating Staphylococcus aureus nasal carriage in chronic haemodialysis patients

Topical 2% mupirocin ointment eradicated chronic Staphylococcus aureus nasal carriage immediately post-therapy in 17 (77%) of 22 haemodialysis patients. Mean time to recurrence was 3.8 weeks. Similar pre-therapy and post-therapy phage types occurred in 12 (71%) of 17 patients. Staphylococcus aureus infections developed in none of 17 successfully treated patients, two of five treatment failures (P = 0.05), and 10 of 46 untreated patients studied concurrently (P = 0.03)

The Size Distribution of Trans-Neptunian Bodies

[Condensed] We search 0.02 deg^2 for trans-Neptunian objects (TNOs) with m<=29.2 (diameter ~15 km) using the ACS on HST. Three new objects are discovered, roughly 25 times fewer than expected from extrapolation of the differential sky density Sigma(m) of brighter objects. The ACS and other recent TNO surveys show departures from a power law size distribution. Division of the TNO sample into ``classical Kuiper belt'' (CKB) and ``Excited'' samples reveals that Sigma(m) differs for the two populations at 96% confidence. A double power law adequately fits all data. Implications include: The total mass of the CKB is ~0.010 M_Earth, only a few times Pluto's mass, and is predominately in the form of ~100 km bodies. The mass of Excited objects is perhaps a few times larger. The Excited class has a shallower bright-end size distribution; the largest objects, including Pluto, comprise tens of percent of the total mass whereas the largest CKBOs are only ~2% of its mass. The predicted mass of the largest Excited body is close to the Pluto mass; the largest CKBO is ~60 times less massive. The deficit of small TNOs occurs for sizes subject to disruption by present-day collisions, suggesting extensive depletion by collisions. Both accretion and erosion appearing to have proceeded to more advanced stages in the Excited class than the CKB. The absence of distant TNOs implies that any distant (60 AU) population must have less than the CKB mass in the form of objects 40 km or larger. The CKB population is sparser than theoretical estimates of the required precursor population for short period comets, but the Excited population could be a viable precursor population.Comment: Revised version accepted to the Astronomical Journal. Numerical results are very slightly revised. Implications for the origins of short-period comets are substantially revised, and tedious material on statistical tests has been collected into a new Appendi

Affective variability in depression:Revisiting the inertia-instability paradox

How can depression be associated with both instability and inertia of affect? Koval et al. (2013, Emotion, 13, 1132) showed that this paradox can be solved by accounting for the statistical overlap between measures of affect dynamics. Nevertheless, these measures are still often studied in isolation. The present study is a replication of the Koval et al. study. We used experience sampling data (three times a day, 1 month) of 462 participants from the general population and a subsample thereof (N = 100) selected to reflect a uniform range of depressive symptoms. Dynamics measures were calculated for momentary negative affect scores. When adjusting for the overlap among affect dynamics measures, depression was associated with 'dispersion' (SD) but not 'instability' (RMSSD) or 'inertia' (AR) of negative affect. The association between dispersion and depression became non-significant when mean levels of negative affect were adjusted for. These findings substantiate the evidence that the presumed association between depression and instability is largely accounted for by the SD, while the association between dispersion and depression may largely reflect mean levels of affect. Depression may thus not be related to higher instability per se, which would be in line with theories on the adaptive function of moment-to-moment fluctuations in affect

Degree of quantum correlation required to speed up a computation

The one clean qubit model of quantum computation (DQC1) efficiently implements a computational task that is not known to have a classical alternative. During the computation, there is never more than a small but finite amount of entanglement present, and it is typically vanishingly small in the system size. In this paper, we demonstrate that there is nothing unexpected hidden within the DQC1 model -- Grover's Search, when acting on a mixed state, provably exhibits a speed-up over classical with guarantees as to the presence of only vanishingly small amounts of quantum correlations (entanglement and quantum discord) -- while arguing that this is not an artefact of the oracle-based construction. We also present some important refinements in the evaluation of how much entanglement may be present in DQC1, and how the typical entanglement of the system must be evaluated.Comment: 7 pages, 3 figure