Unanticipated Partial Behavioral Reflection: Adapting Applications at Runtime

Dynamic, unanticipated adaptation of running systems is of interest in a variety of situations, ranging from functional upgrades to on-the-fly debugging or monitoring of critical applications. In this paper we study a particular form of computational reflection, called unanticipated partial behavioral reflection, which is particularly well-suited for unanticipated adaptation of real-world systems. Our proposal combines the dynamicity of unanticipated reflection, i.e. reflection that does not require preparation of the code of any sort, and the selectivity and efficiency of partial behavioral reflection. First, we propose unanticipated partial behavioral reflection which enables the developer to precisely select the required reifications, to flexibly engineer the metalevel and to introduce the meta behavior dynamically. Second, we present a system supporting unanticipated partial behavioral reflection in Squeak Smalltalk, called Geppetto, and illustrate its use with a concrete example of a web application. Benchmarks validate the applicability of our proposal as an extension to the standard reflective abilities of Smalltalk.

Safe Reflection Through Polymorphism

Code executed in a fully reflective system switches back and forth between application and interpreter code. These two states can be seen as contexts in which an expression is evaluated. Current language implementations obtain reflective capabilities by exposing objects to the interpreter. However, in doing so these systems break the encapsulation of the application objects. In this paper we propose safe reflection through polymorphism, \ie by unifying the interface and ensuring the encapsulation of objects from both the interpreter and application context. We demonstrate a \emphhomogeneous system that defines the execution semantics in terms of itself, thus enforcing that encapsulation is not broken.

Dynamic Synchronization: A Synchronization Model through Behavioral Reflection

In conventional software applications, synchronization code is typically interspersed with functional code, thereby impacting understandability and maintainability of the code base. At the same time, the synchronization defined statically in the code is not capable of adapting to different runtime situations. We propose a new approach to concurrency control which strictly separates the functional code from the synchronization requirements to be used and which adapts objects to be synchronized dynamically to their environment. First-class synchronization specifications express safety requirements, and a dynamic synchronization system dynamically adapts objects to different runtime situations. We present an overview of a prototype of our approach together with several classical concurrency problems, and we discuss open issues for further research.

Reflection of solar wind hydrogen from the lunar surface

The solar wind continuously flows out from the Sun and directly interacts with the surfaces of dust and airless planetary bodies throughout the solar system. A significant fraction of solar wind ions reflect from an object's surface as energetic neutral atoms (ENAs). ENA emission from the Moon was first observed during commissioning of the Interstellar Boundary Explorer (IBEX) mission on 3 December 2008. We present the analysis of 10 additional IBEX observations of the Moon while it was illuminated by the solar wind. For the viewing geometry and energy range (> 250 eV) of the IBEX-Hi ENA imager, we find that the spectral shape of the ENA emission from the Moon is well-represented by a linearly decreasing flux with increasing energy. The fraction of the incident solar wind ions reflected as ENAs, which is the ENA albedo and defined quantitatively as the ENA reflection coefficient RN, depends on the incident solar wind speed, ranging from ~0.2 for slow solar wind to ~0.08 for fast solar wind. The average energy per incident solar wind ion that is reflected to space is 30 eV for slow solar wind and 45 eV for fast solar wind. Once ionized, these ENAs can become pickup ions in the solar wind with a unique spectral signature that reaches 3vSW. These results apply beyond the solar system; the reflection process heats plasmas that have significant bulk flow relative to interstellar dust and cools plasmas having no net bulk flow relative to the dust.

Solar wind reflection from the lunar surface: The view from far and near

The Moon appears bright in the sky as a source of energetic neutral atoms (ENAs). These ENAs have recently been imaged over a broad energy range both from near the lunar surface, by India's Chandrayaan-1 mission (CH-1), and from a much more distant Earth orbit by NASA's Interstellar Boundary Explorer (IBEX) satellite. Both sets of observations have indicated that a relatively large fraction of the solar wind is reflected from the Moon as energetic neutral hydrogen. CH-1's angular resolution over different viewing angles of the lunar surface has enabled measurement of the emission as a function of angle. IBEX in contrast views not just a swath but a whole quadrant of the Moon as effectively a single pixel, as it subtends even at the closest approach no more than a few degrees on the sky. Here we use the scattering function measured by CH-1 to model global lunar ENA emission and combine these with IBEX observations. The deduced global reflection is modestly larger (by a factor of 1.25) when the angular scattering function is included. This provides a slightly updated IBEX estimate of AH=0.11±0.06 for the global neutralized albedo, which is ˜25% larger than the previous values of 0.09±0.05, based on an assumed uniform scattering distribution.

Mapping material distribution in a heterogeneous sand tank by image analysis

Water flow and solute transport through soils are strongly influenced by the spatial arrangement of soil materials with different hydraulic and chemical properties. Knowing the specific or statistical arrangement of these materials is considered as a key toward improved predictions of solute transport. Our aim was to obtain two-dimensional material maps from photographs of exposed profiles. We developed a segmentation and classification procedure and applied it to the images of a very heterogeneous sand tank, which was used for a series of flow and transport experiments. The segmentation was based on thresholds of soil color, estimated from local median gray values, and of soil texture, estimated from local coefficients of variation of gray values. Important steps were the correction of inhomogeneous illumination and reflection, and the incorporation of prior knowledge in filters used to extract the image features and to smooth the results morphologically. We could check and confirm the success of our mapping by comparing the estimated with the designed sand distribution in the tank. The resulting material map was used later as input to model flow and transport through the sand tank. Similar segmentation procedures may be applied to any high-density raster data, including photographs or spectral scans of field profiles.

Plotting regression coefficients and other estimates in Stata

Graphical presentation of regression results has become increasingly popular in the scientific literature, as graphs are much easier to read than tables in many cases. In Stata such plots can be produced by the -marginsplot- command. However, while -marginsplot- is very versatile and flexible, it has two major limitations: it can only process results left behind by -margins- and it can only handle one set of results at the time. In this article I introduce a new command called -coefplot- that overcomes these limitations. It plots results from any estimation command and combines results from several models into a single graph. The default behavior of -coefplot- is to plot markers for coefficients and horizontal spikes for confidence intervals. However, -coefplot- can also produce various other types of graphs. The capabilities of -coefplot- are illustrated in this article using a series of examples.

COEFPLOT: Stata module to plot regression coefficients and other results

coefplot plots results from estimation commands or Stata matrices. Results from multiple models or matrices can be combined in a single graph. The default behavior of coefplot is to draw markers for coefficients and horizontal spikes for confidence intervals. However, coefplot can also produce various other types of graphs.

A 13,600-year diatom oxygen isotope record from the South Carpathians (Romania): Reflection of winter conditions and possible links with North Atlantic circulation changes

This study provides a continuous lateglacial and Holocene record of diatom silica oxygen isotope changes (delta O-18(DIAT)) in a subalpine lake sediment sequence obtained from the Retezat Mts (Taul dintre Brazi, 1740 m a.s.l.). This through-flow, shallow, high-altitude lake with a surface area of only 0.4 ha has short water residence time and is predominantly fed by snowmelt and rainwater. Its delta O-18(DIAT) record principally reflects the oxygen isotope composition of the winter and spring precipitation, as diatom blooms occur mainly in the spring and early summer. Hence, changes in delta O-18(DIAT) are interpreted as seasonal scale changes: in the amount of winter precipitation. Low oxygen isotope values (27-28.5 parts per thousand) occurred during the lateglacial until 12,300 cal BP, followed by a sharp increase thereafter. In the Holocene delta O-18(DIAT) values ranged from 29 to 31 parts per thousand until 3200 cal BP, followed by generally lower values during the late Holocene (27-30 parts per thousand). Short-term decreases in the isotopic values were found between 10,140-9570, 9000-8500, 7800-7300, 6300-5800, 5500-5000 and at 8015, 4400, 4000 cal BP. After 3200 cal BP a decreasing trend was visible with the lowest values between 3100-2500 and after 2100 cal BP The general trend in the record suggests that contribution of winter precipitation was generally lower between 11,680 and 3200 cal BP, followed by increased contribution during the last millennia. The late Holocene decrease in delta O-18(DIAT) shows good agreement with the speleothem delta O-18, lake level and testate amoebae records from the Carpathian Mountains that also display gradual delta O-18 decrease and lake level/mire water table level rise after 3200 cal BR Strong positive correlation with North Atlantic circulation and solar activity proxies, such as the Austrian and Hungarian speleothem records, furthermore suggested that short-term increases in the isotopic ratios in the early and mid Holocene are likely connectable to high solar activity phases and high frequency of positive North Atlantic Oscillation indexes that may have resulted in decreased winter precipitation in this region.