Vibration

Physiological and biomechanical responses of humans to vibrations during manned space flight and threshold data on tolerances to various vibrational modes and condition

Sound and noise

Sound and noise problems in space environment and human tolerance criteria at varying frequencies and intensitie

Pseudo-High-Order Symplectic Integrators

Symplectic N-body integrators are widely used to study problems in celestial mechanics. The most popular algorithms are of 2nd and 4th order, requiring 2 and 6 substeps per timestep, respectively. The number of substeps increases rapidly with order in timestep, rendering higher-order methods impractical. However, symplectic integrators are often applied to systems in which perturbations between bodies are a small factor of the force due to a dominant central mass. In this case, it is possible to create optimized symplectic algorithms that require fewer substeps per timestep. This is achieved by only considering error terms of order epsilon, and neglecting those of order epsilon^2, epsilon^3 etc. Here we devise symplectic algorithms with 4 and 6 substeps per step which effectively behave as 4th and 6th-order integrators when epsilon is small. These algorithms are more efficient than the usual 2nd and 4th-order methods when applied to planetary systems.Comment: 14 pages, 5 figures. Accepted for publication in the Astronomical Journa

Inventory and new records of Polychaete species from the Cap Bon peninsula , North East coast of Tunisia, Western Mediterranean Sea

An inventory of polychaete species is presented from the north-east coast of Tunisia with an historic review of the previous literature from Tunisian coasts. Altogether 40 families, 146 genera, and 238 species are currently known from the area, of which 86 taxa, 4 families (Chrysopetalidae, Pilargidae, Protodrilidae and Saccocirridae) and 40 genera (Saccocirrus, Protodrilus, Parathelepus, Thelepus, Petta, Isolda, Brada, Tharyx, Paraprionospio, Jasmineira, Hypsicomus, Euchone, Pseudobranchiomma, Laonome, Galathowenia, Lugia, Pseudomystides, Protomystides, Pirakia, Mysta, Eurysyllis, Parapionosyllis, Streptosyllis, Paraehlersia, Sigambra, Ancistrosyllis, Kefersteinia, Chrysopetalum, Bhawania, Fimbriosthenelais, Subadyte, Panthalis, Dorvillea, Scalibregma, Paradoneis, Cirrophorus, Metasychis, Websterinereis, Euniphysa and Mastobranchus) are new additions to the polychaete fauna of Tunisia. The list, which provides a synthesis of the regional taxonomic work, including coastal areas from Sidi Daoud to the area of Menzel Hurr (Cap Bon Peninsula, Western Mediterranean Sea), can serve as a baseline for future studies

Monitoring Networked Applications With Incremental Quantile Estimation

Networked applications have software components that reside on different computers. Email, for example, has database, processing, and user interface components that can be distributed across a network and shared by users in different locations or work groups. End-to-end performance and reliability metrics describe the software quality experienced by these groups of users, taking into account all the software components in the pipeline. Each user produces only some of the data needed to understand the quality of the application for the group, so group performance metrics are obtained by combining summary statistics that each end computer periodically (and automatically) sends to a central server. The group quality metrics usually focus on medians and tail quantiles rather than on averages. Distributed quantile estimation is challenging, though, especially when passing large amounts of data around the network solely to compute quality metrics is undesirable. This paper describes an Incremental Quantile (IQ) estimation method that is designed for performance monitoring at arbitrary levels of network aggregation and time resolution when only a limited amount of data can be transferred. Applications to both real and simulated data are provided.Comment: This paper commented in: [arXiv:0708.0317], [arXiv:0708.0336], [arXiv:0708.0338]. Rejoinder in [arXiv:0708.0339]. Published at http://dx.doi.org/10.1214/088342306000000583 in the Statistical Science (http://www.imstat.org/sts/) by the Institute of Mathematical Statistics (http://www.imstat.org

Rejoinder: Monitoring Networked Applications With Incremental Quantile Estimation

Rejoinder: Monitoring Networked Applications With Incremental Quantile Estimation [arXiv:0708.0302]Comment: Published at http://dx.doi.org/10.1214/088342306000000592 in the Statistical Science (http://www.imstat.org/sts/) by the Institute of Mathematical Statistics (http://www.imstat.org

The ‘Little Ice Age’ in the Southern Hemisphere in the context of the last 3000 years : Peat-based proxy-climate data from Tierra del Fuego

DM’s research (at Department of Earth Sciences, Uppsala University) was supported through a European Community Marie Curie Fellowship (Contract HPMF-CT-2000-01056).Peer reviewedPostprin

Testing for seasonal unit roots by frequency domain regression

This paper develops univariate seasonal unit root tests based on spectral regression estimators. An advantage of the frequency domain approach is that it enables serial correlation to be treated non-parametrically. We demonstrate that our proposed statistics have pivotal limiting distributions under both the null and near seasonally integrated alternatives when we allow for weak dependence in the driving shocks. This is in contrast to the popular seasonal unit root tests of, among others, Hylleberg et al. (1990) which treat serial correlation parametrically via lag augmentation of the test regression. Moreover, our analysis allows for (possibly infinite order) moving average behaviour in the shocks, while extant large sample results pertaining to the Hylleberg et al. (1990) type tests are based on the assumption of a finite autoregression. The size and power properties of our proposed frequency domain regression-based tests are explored and compared for the case of quarterly data with those of the tests of Hylleberg et al. (1990) in simulation experiments.Seasonal unit root tests; moving average; frequency domain regression; spectral density estimator; Brownian motion

Breakdown of weak-field magnetotransport at a metallic quantum critical point

We show how the collapse of an energy scale in a quantum critical metal can lead to physics beyond the weak-field limit usually used to compute transport quantities. For a density-wave transition we show that the presence of a finite magnetic field at the critical point leads to discontinuities in the transport coefficients as temperature tends to zero. The origin of these discontinuities lies in the breakdown of the weak field Jones-Zener expansion which has previously been used to argue that magneto-transport coefficients are continuous at simple quantum critical points. The presence of potential scattering and magnetic breakdown rounds the discontinuities over a window determined by tau Delta < 1 where Delta is the order parameter and tau is the quasiparticle elastic lifetime.Comment: 4 pages, 3 figures RevTeX forma