Branching Space-Times and Parallel Processing

There is a remarkable similarity between some mathematical objects used in the Branching Space-Times framework and those appearing in computer science in the fields of event structures for concurrent processing and Chu spaces. This paper introduces the similarities and formulates a few open questions for further research, hoping that both BST theorists and computer scientists can benefit from the project

On Minkowskian Branching Structures

We introduce the notion of a Minkowskian Branching Structure ("MBS" for short). Then we prove some results concerning the phenomenon of funny business in its finitary and infinitary variants

Only countable common cause systems exist

In this paper we give a positive answer to a problem posed by G. Hofer-Szabo and M. Redei (2004) regarding the existence of infinite common cause systems (CCSs). An example of a countably infinite CCS is presented, as well as the proof that no CCSs of greater cardinality exist

Completion of the Causal Completability Problem

We give a few results concerning the notions of causal completability and causal closedness of classical probability spaces (Hofer-Szabó, Rédei & Szabó [1999], Gyenis & Rédei [2004]). Answering a question from Hofer-Szabó et al. [1999], we prove that any classical probability space has a causally closed extension. We also employ the notion of causal up-to-n-closedness (Wroński & Marczyk [2010a]) to show that any finite classical probability space with rational probabilities on the atoms of the event algebra can be extended to a finite space which is causally up-to-3-closed. Lastly, we prove that any classical probability space can be extended to a space in which all correlations between events which are logically independent modulo measure zero event have a countably infinite common cause system (for the definition of the latter notion, see Hofer-Szabó & Rédei [2004]). Collectively, these results show that it is surprisingly easy to find Reichenbach-style explanations for correlations, underlining doubts as to whether this approach can yield a philosophically relevant account of causality

Light-induced effects-impacts to module performance measurements and reliability testing: An overview

The stability of solar cells is a key factor in determining the reliability of photovoltaic modules and is of great interest in the case of solar cells having a new technology which has not yet been fully developed. In particular this question arises with hydrogenated amorphous silicon (a-Si) solar cells because a-Si exhibits reversible light induced changes in its electronic properties, commonly referred to as the Staebler-Wronski effect (SWE). Continuous progress is being made in the peak conversion efficiencies of a-Si solar cells and efficiencies in excess of 11% have been achieved. However, stability is still a problem. ARCO Solar reports results on solar cells which, after over a year's exposure to sunlight, under open circuit conditions, still have about 7% conversion efficiency. Other results show a region of fast degradation for about a month, after which the degradation diminishes rapidly

Changes in bone structure and metabolism during simulated weightlessness: Endocrine and dietary factors

The role of vitamin D, PTH and corticosterone in the skeletal alterations induced by simulated weightlessness was examined. The first objective was to determine if changes in the serum concentrations of Ca, P sub i, osteocalcin, 25-OH-D, 24,25(OH)2D or 1,25(OH)2D also occur following acute skeletal unloading. Animals were either suspended or pair fed for 2, 5, 7, 10, 12 and 15 days and the serum concentrations of Ca, P sub i, osteocalcin and the vitamin D metabolites measured. Bone histology was examined at day 5 after suspension. Acute skeletal unloading produced a transient hypercalcemia, a significant fall in serum osteocalcin and serum 1,25(OH)2D, a slight rise in serum 24,25(OH)2D, but did not affect the serum concentrations of P sub i or 25-OH-D. At the nadir in serum 1,25(OH)2D serum osteocalcin was reduced by 22%, osteoblast surface by 32% and longitudinal bone growth by 21%

The effect of crystallite size on the melting point of tin

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Seasonality of group size and group composition in Sand Partridges (Ammoperdix heyi heyi).

The seasonality of group size and composition in sand partridges was studied at the Ibex Reserve in central Saudi Arabia. Mean group size and fl ock encounter rate were signifi cantly related to rainfall and temperature. During winter and the breeding season (March to April), the encounter rate on the valley fl oors was distinctly lower than that observed during summer. Although encounter rates did not diff er signifi cantly between valleys, sand partridges were more likely to be encountered in narrow, stony valleys. Correcting for valley width, encounter rates did not diff er between valleys. Male and female encounter rates were constant throughout the reserve, indicating a constant sex ratio throughout the year. Results are in line with earlier fi ndings reported from more northern habitats such as the Eilat Mountains (Israel) and the Rum Wildlife Reserve (Jordan). Human disturbance in parts of the reserve is high and may have an impact on group size and composition