Communicating Mobile Processes

This paper presents a new model for mobile processes in occam-pi. A process, embedded anywhere in a dynamically evolving network, may suspend itself mid-execution, be safely disconnected from its local environment, moved (by communication along a channel), reconnected to a new environment and reactivated. Upon reactivation, the process resumes execution from the same state (i.e. data values and code positions) it held when it suspended. Its view of its environment is unchanged, since that is abstracted by its synchronisation (e.g. channels and barriers) interface and that remains constant. The environment behind that interface will (usually) be completely different. The mobile process itself may contain any number of levels of dynamic sub-network. This model is simpler and, in some ways, more powerful than our earlier proposal, which required a process to terminate before it could be moved. Its formal semantics and implementation, however, throw up extra challenges. We present details and performance of an initial implementation

Threshold Photo/Electro Pion Production - Working Group Summary

We summarize the pertinent experimental and theoretical developments in the field of pion photo- and electroproduction in the threshold region. We discuss which experiments and which calculations should be done/performed in the future.Comment: plain TeX (macro included), 6pp, summary talk presented at the workshop on "Chiral Dynamics: Theory and Experiments", MIT, July 25-29, 199

Altered brain ion gradients following compensation for elevated CO2 are linked to behavioural alterations in a coral reef fish

Neurosensory and behavioural disruptions are some of the most consistently reported responses upon exposure to ocean acidification-relevant CO2 levels, especially in coral reef fishes. The underlying cause of these disruptions is thought to be altered current across the GABAA receptor in neuronal cells due to changes in ion gradients (HCO3− and/or Cl−) that occur in the body following compensation for elevated ambient CO2. Despite these widely-documented behavioural disruptions, the present study is the first to pair a behavioural assay with measurements of relevant intracellular and extracellular acid-base parameters in a coral reef fish exposed to elevated CO2. Spiny damselfish (Acanthochromis polyacanthus) exposed to 1900 μatm CO2 for 4 days exhibited significantly increased intracellular and extracellular HCO3− concentrations and elevated brain pHi compared to control fish, providing evidence of CO2 compensation. As expected, high CO2 exposed damselfish spent significantly more time in a chemical alarm cue (CAC) than control fish, supporting a potential link between behavioural disruption and CO2 compensation. Using HCO3− measurements from the damselfish, the reversal potential for GABAA (EGABA) was calculated, illustrating that biophysical properties of the brain during CO2 compensation could change GABAA receptor function and account for the behavioural disturbances noted during exposure to elevated CO2

Magnesium in plants: uptake, distribution, function, and utilization by man and animals

Plants provide man with his primary needs--nutrition, clothing, and shelter as well as medicinal, recreational, and esthestic benefits. There are over 500,000 species of plants distributed over the earth. Magnesium is an essential nutrient for plants and animals. The criteria for the essentiality of elements for plants are as follows: (1) the plant will be unable to complete its life cycle if the element is removed from the plant nutrient medium; (2) the element has a specific function which cannot be replaced by other elements; or (3) the element is a necessary component of an essential metabolite [1]. The relative abundance of Mg in plant life is less than N, K, Ca, and similar to S and P. Intensive crop production practices with fertilizers, improved plant cultivars, and best management practices are commonly used today. These intense cultural practices may mean an increasing frequency of Mg deficiencies as well as the need for knowledge on economically sound practices to prevent such deficiencies. Plants are an important source of Mg to satisfy human and animal requirements, and factors affecting Mg bioavailability need to be identified. The objective of this chapter is to assess the importance, distribution, function, and utilization of Mg in plant growth and metabolism and in grazing ruminant animal production and human health

Fast Searching in Packed Strings

Given strings $P$ and $Q$ the (exact) string matching problem is to find all positions of substrings in $Q$ matching $P$. The classical Knuth-Morris-Pratt algorithm [SIAM J. Comput., 1977] solves the string matching problem in linear time which is optimal if we can only read one character at the time. However, most strings are stored in a computer in a packed representation with several characters in a single word, giving us the opportunity to read multiple characters simultaneously. In this paper we study the worst-case complexity of string matching on strings given in packed representation. Let $m \leq n$ be the lengths $P$ and $Q$, respectively, and let $\sigma$ denote the size of the alphabet. On a standard unit-cost word-RAM with logarithmic word size we present an algorithm using time O\left(\frac{n}{\log_\sigma n} + m + \occ\right). Here \occ is the number of occurrences of $P$ in $Q$. For $m = o(n)$ this improves the $O(n)$ bound of the Knuth-Morris-Pratt algorithm. Furthermore, if $m = O(n/\log_\sigma n)$ our algorithm is optimal since any algorithm must spend at least \Omega(\frac{(n+m)\log \sigma}{\log n} + \occ) = \Omega(\frac{n}{\log_\sigma n} + \occ) time to read the input and report all occurrences. The result is obtained by a novel automaton construction based on the Knuth-Morris-Pratt algorithm combined with a new compact representation of subautomata allowing an optimal tabulation-based simulation.Comment: To appear in Journal of Discrete Algorithms. Special Issue on CPM 200

Quantum Coherence in a Single Ion due to strong Excitation of a metastable Transition

We consider pump-probe spectroscopy of a single ion with a highly metastable (probe) clock transition which is monitored by using the quantum jump technique. For a weak clock laser we obtain the well known Autler-Townes splitting. For stronger powers of the clock laser we demonstrate the transition to a new regime. The two regimes are distinguished by the transition of two complex eigenvalues to purely imaginary ones which can be very different in magnitude. The transition is controlled by the power of the clock laser. For pump on resonance we present simple analytical expressions for various linewidths and line positions.Comment: 6 figures. accepted for publication in PR

Phenotypic Diversity for Seed Mineral Concentration in North American Dry Bean Germplasm of Middle American Ancestry

Dry bean (Phaseolus vulgaris L.) seeds are a major protein, carbohydrate, and mineral source in the human diet of peoples in multiple regions of the world. Seed mineral biofortification is an ongoing objective to improve this important food source. The objective of this research was to assess the seed mineral concentration of five macroelements and eight microelements in a large panel (n = 277) of modern race Durango and race Mesoamerica genotypes to determine if variability existed that could be exploited for targeted seed biofortification. Varieties that derive from these races are found in many diets throughout the world. The panel was grown in replicated trials under typical production conditions in the major bean growing regions of the United States, and a subset of the panel was also grown in replicated trials at three locations under control and terminal drought conditions. Except for K, seed mineral concentrations were higher for race Mesoamerica genotypes. Significantly higher seed concentrations for the majority of the minerals were observed for white-seeded genotypes and race Durango genotypes with the now preferred indeterminate, upright growth habit. Modern genotypes (since 1997) had equal or increased mineral concentrations compared with older genotypes. Drought affected mineral content differentially, having no effect on the microelement content but increased Co, Fe, and Ni concentrations. The correlation of Ca and Mn concentrations suggests that these elements may share seed deposition mechanisms. The high heritability for seed mineral concentration implies that breeding progress can be achieved by parental selection from this panel

A proof of the Geroch-Horowitz-Penrose formulation of the strong cosmic censor conjecture motivated by computability theory

In this paper we present a proof of a mathematical version of the strong cosmic censor conjecture attributed to Geroch-Horowitz and Penrose but formulated explicitly by Wald. The proof is based on the existence of future-inextendible causal curves in causal pasts of events on the future Cauchy horizon in a non-globally hyperbolic space-time. By examining explicit non-globally hyperbolic space-times we find that in case of several physically relevant solutions these future-inextendible curves have in fact infinite length. This way we recognize a close relationship between asymptotically flat or anti-de Sitter, physically relevant extendible space-times and the so-called Malament-Hogarth space-times which play a central role in recent investigations in the theory of "gravitational computers". This motivates us to exhibit a more sharp, more geometric formulation of the strong cosmic censor conjecture, namely "all physically relevant, asymptotically flat or anti-de Sitter but non-globally hyperbolic space-times are Malament-Hogarth ones". Our observations may indicate a natural but hidden connection between the strong cosmic censorship scenario and the Church-Turing thesis revealing an unexpected conceptual depth beneath both conjectures.Comment: 16pp, LaTeX, no figures. Final published versio

Separation of the Longitudinal and Transverse Cross Sections in the p(e, e′K+)Λ and p(e, e′K+)Σ0 Reactions

We report measurements of cross sections for the reaction p(e,e′K+)Y, for both the Λ and Σ0 hyperon states, at an invariant mass of W =1.84 GeV and four-momentum transfers 0.5 < Q2 < 2 (GeV/c)2. Data were taken for three values of virtual photon polarization ε, allowing the decom- position of the cross sections into longitudinal and transverse components. The Λ data is a revised analysis of prior work, whereas the Σ0 results have not been previously reported