A novel chromosome segregation mechanism during female meiosis.

In a wide range of eukaryotes, chromosome segregation occurs through anaphase A, in which chromosomes move toward stationary spindle poles, anaphase B, in which chromosomes move at the same velocity as outwardly moving spindle poles, or both. In contrast, Caenorhabditis elegans female meiotic spindles initially shorten in the pole-to-pole axis such that spindle poles contact the outer kinetochore before the start of anaphase chromosome separation. Once the spindle pole-to-kinetochore contact has been made, the homologues of a 4-μm-long bivalent begin to separate. The spindle shortens an additional 0.5 μm until the chromosomes are embedded in the spindle poles. Chromosomes then separate at the same velocity as the spindle poles in an anaphase B-like movement. We conclude that the majority of meiotic chromosome movement is caused by shortening of the spindle to bring poles in contact with the chromosomes, followed by separation of chromosome-bound poles by outward sliding

Orbital dynamics of large solar power satellites

Designs for geostationary SPS are extremely large in scale, more than an order of magnitude larger than the International Space Station. The problem of how to control the orbital motion of such large structures, accounting for various perturbing forces, is therefore a topic worthy of further study. The primary objective of the proposed research is to perform a detailed study of SPS orbit dynamics, obtaining a comprehensive understanding of the effect of perturbations on orbits of large SPS structures over a time-frame commensurate with proposed SPS lifetimes (30-40 years). Analytical equations derived by the process of averaging of the SPS equations of motion shall be used in determining the long-term orbital behaviour. Previous studies have simply assumed a geostationary orbit (GEO) then designed control systems for maintaining it thus. It is found that an alternative SPS orbital location known as the geosynchronous Laplace plane (GLP) is superior to GEO. An SPS in GLP requires virtually no fuel to maintain its orbit, avoids the main orbital debris population originating from GEO satellites and is extremely robust, i.e. loss of control is inconsequential. The GLP SPS saves of order 10<sup>4</sup> to 10<sup>5</sup> kg per year in fuel compared to a GEO SPS for equivalent power delivery compared to GEO

A Performer\u27s Analysis of Eric Ewazen\u27s Sonata for Trumpet and Piano

Eric Ewazen is a prolific composer whose works are becoming standard repertoire for not only trumpet players but also for brass quintets, soloists, and wind ensembles alike. Ewazen wrote the Sonata for Trumpet and Piano for the International Trumpet Guild, and it was premiered by Chris Gekker, trumpet, and Ewazen, piano, in 1995 in Bloomington, Indiana. This document illuminates some of the characteristics of Ewazen\u27s music, and summarizes the music\u27s technical and performance demands, based on firsthand performing experience. It should also offer practical observations and recommendations for the performance of Eric Ewazen\u27s Sonata for Trumpet and Piano

U.S. pension fund investment in real estate : a twenty-five year history & five year forecast

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Urban Studies and Planning, 1996.Includes bibliographical references (leaves 89-91).by Daniel Paul McCadden & Peter Timothy McNally.M.S

Front-Running Protection for Distributed Exchanges using Tamper-Resistant Round Trip Time Measurements

In this paper we present ODIN, a front-running protection system that uses a novel algorithm to measure Round-Trip-Time (RTT) to untrusted servers. ODIN is the decentralized equivalent of THOR, a RTT-aware front-running protection system for trading on centralized exchanges. Unlike centralized exchanges, P2P exchanges have potentially malicious peers which makes reliable direct RTT measurement impossible. In order to prevent tampering by an arbitrarily malicious peer, ODIN performs an indirect RTT measurement that never interacts directly with the target machine. The RTT to the target is estimated by measuring the RTT to a randomized IP address that is known to be close to the target's IP address in the global routing network. We find that ODIN's RTT estimation algorithm provides an accurate, practical, and generic solution for collecting network latency data in a hostile network environment

Dynactin-dependent cortical dynein and spherical spindle shape correlate temporally with meiotic spindle rotation in Caenorhabditis elegans.

Oocyte meiotic spindles orient with one pole juxtaposed to the cortex to facilitate extrusion of chromosomes into polar bodies. In Caenorhabditis elegans, these acentriolar spindles initially orient parallel to the cortex and then rotate to the perpendicular orientation. To understand the mechanism of spindle rotation, we characterized events that correlated temporally with rotation, including shortening of the spindle in the pole-to pole axis, which resulted in a nearly spherical spindle at rotation. By analyzing large spindles of polyploid C. elegans and a related nematode species, we found that spindle rotation initiated at a defined spherical shape rather than at a defined spindle length. In addition, dynein accumulated on the cortex just before rotation, and microtubules grew from the spindle with plus ends outward during rotation. Dynactin depletion prevented accumulation of dynein on the cortex and prevented spindle rotation independently of effects on spindle shape. These results support a cortical pulling model in which spindle shape might facilitate rotation because a sphere can rotate without deforming the adjacent elastic cytoplasm. We also present evidence that activation of spindle rotation is promoted by dephosphorylation of the basic domain of p150 dynactin

An equivariant Reeb-Beltrami correspondence and the Kepler-Euler flow

We prove that the correspondence between Reeb and Beltrami vector fields can be made equivariant whenever additional symmetries of the underlying geometric structures are considered. As a corollary of this correspondence, we show that energy levels above the maximum of the potential energy of mechanical Hamiltonian systems can be viewed as stationary fluid flows, though the metric is not prescribed. In particular, we showcase the emblematic example of the $n$-body problem and focus on the Kepler problem. We explicitly construct a compatible Riemannian metric that makes the Kepler problem of celestial mechanics a stationary fluid flow (of Beltrami type) on a suitable manifold, the Kepler-Euler flow.Comment: 16 pages, 3 figures. Overall improvements of the paper. Final section adde

Experimental axial-compressive behaviour of bare cold-formed-steel studs with semirigid-track and ideal-hinged boundary-conditions

Studs are the primary load-bearing components in cold-formed steel (CFS) wall panels, connected to tracks at both ends with self-tapping screws, forming a semirigid boundary condition (BCT). Most existing tests on the axial compressive behaviour of bare CFS studs are based on either theoretically-hinged (BCH) or fully-fixed boundary conditions. Previous researchers have employed BCT only on sheathed stud-wall panels. However, practicing engineers and current design codes, e.g., Eurocode 3, follow an all-steel design. Therefore, this research experimentally investigated bare-CFS-studs' axial compressive behaviour with BCT, considering, for the first time, the combined effect of the tracks' warping rigidity, stud-to-track gap, non-linear connection stiffness, and bare studs' various cross-sectional slenderness. Forty-two industry-standard lipped channel sections (studs) of five thicknesses (1.2-3 mm), three depths (75–125 mm), and two heights (1.2 & 1.5 m) were tested under static-concentric axial compressive loading with BCT. Another fourteen studs were tested with BCH, a comparator to BCT. Results demonstrated that the studs' global failure mechanisms were flexural-torsional in BCT instead of flexural in BCH. Studs' axial stiffness was two-phased in BCT due to the stud-to-track gap, compared to single-phased stiffness in BCH. >1.8 mm stud-to-track gap caused stud-to-track connections' failure and studs' sudden capacity reduction during gap closure. Studs achieved 1.22 times higher axial-compressive strength, 2.3 times more axial-shortening, 0.7 times lower axial stiffness, and 58% lower axial-compressive strain at the web-midheight under BCT-PhaseII than BCH. Tested strengths were compared with EC3 design strength, and an effective-length-factor of 0.65 was suggested for efficient design of studs with BCT

2N or infinitely many escape orbits

In this short note, we prove that singular Reeb vector fields associated with generic Melrose-type $b$-contact forms have either (at least) $2N$ or an infinite number of escape orbits, where $N$ denotes the number of connected components of the critical set. We obtain this result as a corollary of the same statement for the number of escape orbits of singular Beltrami fields using the singular version of Etnyre-Ghrist's contact/Beltrami correspondence.Comment: 12 pages, for Alain Chenciner on his 2N-birthda

Examining patient benefit

Healthcare policy, clinical practice and clinical research all declare patient benefit as their avowed aim. Yet, the conceptual question of what exactly constitutes patient benefit has received much less attention than the practical means of realising it. Currently, three key areas of conceptual unclarity make the achieved, real-world impact hard to quantify and disconnect it from the magnitude of the practical endeavour: (1) the distinction between objective and subjective benefit, (2) the relation between individual and population measures of benefit, and (3) the optimal measurement of benefit in research studies. A philosophical understanding of wellbeing is required to clarify these problems. Adopting a rigorous philosophical framework makes apparent that the differing goals of clinicians, researchers and research funders may make differing conceptions of patient benefit appropriate. A framework is proposed for developing rigour in methods for specifying and measuring patient benefit, and for matching benefit measures to different contexts