PKI Interoperability: Still an Issue? A Solution in the X. 509 Realm

There exist many obstacles that slow the global adoption of public key infrastructure (PKI) technology. The PKI interoperability problem, being poorly understood, is one of the most confusing. In this paper, we clarify the PKI interoperability issue by exploring both the juridical and technical domains. We demonstrate the origin of the PKI interoperability problem by determining its root causes, the latter being legal, organizational and technical differences between countries, which mean that relying parties have no one to rely on. We explain how difficult it is to harmonize them. Finally, we propose to handle the interoperability problem from the trust management point of view, by introducing the role of a trust broker which is in charge of helping relying parties make informed decisions about X.509 certificates

The Detectability of Transit Depth Variations due to Exoplanetary Oblateness and Spin Precession

Knowledge of an exoplanet's oblateness and obliquity would give clues about its formation and internal structure. In principle, a light curve of a transiting planet bears information about the planet's shape, but previous work has shown that the oblateness-induced signal will be extremely difficult to detect. Here we investigate the potentially larger signals due to planetary spin precession. The most readily detectable effects are transit depth variations (T$\delta$V) in a sequence of light curves. For a planet as oblate as Jupiter or Saturn, the transit depth will undergo fractional variations of order 1%. The most promising systems are those with orbital periods of approximately 15--30 days, which is short enough for the precession period to be less than about 40 years, and long enough to avoid spin-down due to tidal friction. The detectability of the T$\delta$V signal would be enhanced by moons (which would decrease the precession period) or planetary rings (which would increase the amplitude). The Kepler mission should find several planets for which precession-induced T$\delta$V signals will be detectable. Due to modeling degeneracies, Kepler photometry would yield only a lower bound on oblateness. The degeneracy could be lifted by observing the oblateness-induced asymmetry in at least one transit light curve, or by making assumptions about the planetary interior.Comment: Accepted for publication in The Astrophysical Journa

A Smaller Radius for the Transiting Exoplanet WASP-10b

We present photometry of WASP-10 during the transit of its short-period Jovian planet. We employed the novel PSF-shaping capabilities the OPTIC camera mounted on the UH 2.2m telescope to achieve a photometric precision of 4.7e-4 per 1.3 min sample. With this new light curve, in conjunction with stellar evolutionary models, we improve on existing measurements of the planetary, stellar and orbital parameters. We find a stellar radius Rstar = 0.698 +/- 0.012 Rsun and a planetary radius Rp = 1.080 +/- 0.020 Rjup. The quoted errors do not include any possible systematic errors in the stellar evolutionary models. Our measurement improves the precision of the planet's radius by a factor of 4, and revises the previous estimate downward by 16% (2.5sigma, where sigma is the quadrature sum of the respective confidence limits). Our measured radius of WASP-10b is consistent with previously published theoretical radii for irradiated Jovian planets.Comment: 4 pages, 2 tables, 2 figures, table 1 available upon reques

Line-profile tomography of exoplanet transits I: The Doppler shadow of HD 189733b

We present a direct method for isolating the component of the starlight blocked by a planet as it transits its host star, and apply it to spectra of the bright transiting planet HD 189733b. We model the global shape of the stellar cross-correlation function as the convolution of a limb-darkened rotation profile and a gaussian representing the Doppler core of the average photospheric line profile. The light blocked by the planet during the transit is a gaussian of the same intrinsic width, whose trajectory across the line profile yields a precise measure of the misalignment angle and an independent measure of v sin I. We show that even when v sin I is less than the width of the intrinsic line profile, the travelling Doppler "shadow" cast by the planet creates an identifiable distortion in the line profiles which is amenable to direct modelling. Direct measurement of the trajectory of the missing starlight yields self-consistent measures of the projected stellar rotation rate, the intrinsic width of the mean local photospheric line profile, the projected spin-orbit misalignment angle, and the system's centre-of-mass velocity. Combined with the photometric rotation period, the results give a geometrical measure of the stellar radius which agrees closely with values obtained from high-precision transit photometry if a small amount of differential rotation is present in the stellar photosphere.Comment: 8 pages, 5 figures, 2 tables; accepted by MNRA

Evaluation of a series hybird thrust bearing at DN values to three million. 1: Analysis and design

The analysis and design are presented of a hybrid bearing consisting of a 150-mm ball bearing and a centrifugally actuated, conical, fluid film bearing fitting an envelope with an outer radius of 86.4 mm (3.4 in.) and an inner radius of 71 mm (2.8 in.). The bearing analysis, combined with available torque data on ball bearings, indicates that an effective speed split between the ball and fluid-film bearings of 50 percent may be expected during operation at 20,000 rpm and under an axial load of 17,800 newtons (4000 lbs.). This speed split can result in a ten-fold increase in the life of the ball bearing when compared to a simple ball bearing system operating under similar conditions

Assessment of geophysical flows for zero-gravity simulation

The results of research relating to the feasibility of using a low gravity environment to model geophysical flows are presented. Atmospheric and solid earth flows are considered. Possible experiments and their required apparatus are suggested

Freedom at Midday: Elements of Existentialism in the Works of Ambrose Bierce

Ambrose Bierce exhibited a number of elements of existential thinking both in his life and in his writing. But he was ambivalent about his philosophical stance, and it is difficult to know whether he was the utter pessimist he has been called, or whether his attitude toward the universe admitted a certain optimism. Much of Bierce\u27s thought parallels modern existentialism, which has three main tenets: a belief that there is no God and the universe is, therefore, irrational; a descent into despair; and a choice of life or death. Bierce insisted that the universe is irrational, and he repeatedly discussed the death, cruelty or mutability of God. His heroes often felt the Angst of existential despair, but Bierce remained ambivalent about the alternatives in such a chaotic universe. Bierce\u27s war stories illustrate the existential moment when the hero confronts the absurd universe. Many of Bierce\u27s heroes commit suicide in despair, but a few choose a more meaningful death, a finite transcendence in the face of the irrational which results in a sort of affirmation of the power of mankind within a universe of chaos. This study examines two of these stories, The Mocking-bird and A Son of the Gods, with reference to the existential thought they demonstrate. Bierce was a proto-existentialist; his approach to the universe prefigured twentieth century existential thought, and within this framework, we find that he was not a complete pessimist, but that he discovered the very circumstances that would be the basis of optimistic existentialism in the twentieth century

Non-maternal infant care among the Efe and Lese of Zaire : how much and by whom.

This study examined infant caretaking practices among the Efe (Pygmies) and Lese, who inhabit the Ituri Forest in northeastern Zaire. The data presented here, collected as part of a larger study of child development among these people, focus on two related questions. First, to what extent are infants\u27 mothers their primary caretakers during their first months of life? And second, who are the other individuals responsible for infants\u27 care? Ten Efe and nine Lese infants were observed longitudinally. Naturalistic observations were made when infants were 3, 7, and 18 weeks old, using an event sequence format with the infant as the focal subject. The behavioral scoring system noted the occurrence of, or any changes in, the ongoing behavior of infant or caretaker, as well as caretaker identity, in each one-minute interval. Four measures of infants\u27 contacts with caretakers were derived: percentage of intervals infants were in physical contact with various caretakers; the rate at which infants were transferred among caretakers; the mean length, in intervals, of caretaking bouts; and the mean number of individuals who held the infant in an observation period. Descriptive data and comparisons of caretaking by mothers and other caretakers are presented. Analyses examine non-maternal caretakers\u27 age, gender, familial relationship to the infant, and the reproductive status of adult female caretakers. Data reveal that Efe and Lese caretaking practices include extensive participation by non-maternal caretakers. Efe infants spent more than 50%, and Lese infants almost 40% of the time with caretakers other than their mothers, and were passed to these caretakers more often than to their mothers. Infants spent little time out of physical contact with a caretaker. Effects of group membership and infant age on contributions by various classes of caretakers are presented. The findings are discussed with respect to models of mother-infant contact during the first months of life. Models such as the continuous care and contact or the bonding model, which place narrow and rigid constraints on the range of acceptable human caretaking practices are challenged, and a more culturally sensitive strategic model is proposed