Moving in time: simulating how neural circuits enable rhythmic enactment of planned sequences

Many complex actions are mentally pre-composed as plans that specify orderings of simpler actions. To be executed accurately, planned orderings must become active in working memory, and then enacted one-by-one until the sequence is complete. Examples include writing, typing, and speaking. In cases where the planned complex action is musical in nature (e.g. a choreographed dance or a piano melody), it appears to be possible to deploy two learned sequences at the same time, one composed from actions and a second composed from the time intervals between actions. Despite this added complexity, humans readily learn and perform rhythm-based action sequences. Notably, people can learn action sequences and rhythmic sequences separately, and then combine them with little trouble (Ullén & Bengtsson 2003). Related functional MRI data suggest that there are distinct neural regions responsible for the two different sequence types (Bengtsson et al. 2004). Although research on musical rhythm is extensive, few computational models exist to extend and inform our understanding of its neural bases. To that end, this article introduces the TAMSIN (Timing And Motor System Integration Network) model, a systems-level neural network model capable of performing arbitrary item sequences in accord with any rhythmic pattern that can be represented as a sequence of integer multiples of a base interval. In TAMSIN, two Competitive Queuing (CQ) modules operate in parallel. One represents and controls item order (the ORD module) and the second represents and controls the sequence of inter-onset-intervals (IOIs) that define a rhythmic pattern (RHY module). Further circuitry helps these modules coordinate their signal processing to enable performative output consistent with a desired beat and tempo.Accepted manuscrip

Conformal Invariance and Duality in Self-Dual Gravity and (2,1) Heterotic String Theory

A system of gravity coupled to a 2-form gauge field, a dilaton and Yang-Mills fields in $2n$ dimensions arises from the (2,1) sigma model or string. The field equations imply that the curvature with torsion and Yang-Mills field strength are self-dual in four dimensions, or satisfy generalised self-duality equations in $2n$ dimensions. The Born-Infeld-type action describing this system is simplified using an auxiliary metric and shown to be classically Weyl invariant only in four dimensions. A dual form of the action is found (no isometries are required). In four dimensions, the dual geometry is self-dual gravity without torsion coupled to a scalar field. In $D>4$ dimensions, the dual geometry is hermitian and determined by a $D-4$ form potential $K$, generalising the K\"{a}hler potential of the four dimensional case, with the fundamental 2-form given by $\tilde J= i*\partial \bar \partial K$. The coupling to Yang-Mills is through a term $K\wedge tr (F\wedge F)$ and leads to a Uhlenbeck-Yau field equation $\tilde J^{ij}F_{ij}=0$.Comment: LaTeX, 14 pages, no figures. One reference added and interpretation revised; version to appear in Physics Letters

Multi-Sectoral Uses of Water & Approaches to DSS in Water Management in the NOSTRUM Partner Countries of the Mediterranean

Agriculture contributes an average of about 10% to the GDP of the partner countries of the Mediterranean involved in the project NOSTRUM. On the other hand, industry contributes an average of about 30% in these countries. It is to remark that in almost all countries the weight of industry accounts between 20% and 30% of the national economy, with the exception of Algeria, where this weight is at about 60%, mainly imputable to the great development of oil extraction and energy sector. In the majority of participating countries, agriculture sector is the greatest consumer of water (more than 65% of total water consumption). Although the case from France where agriculture water use is only about 10% of total water consumption and Italy with around 45%, but this may be due to the fact that most countries reporting for their agricultural water consumption do not include the amount of rain-fed to cultivated lands as a part of their agriculture water use. Most agriculture water use is limited to irrigation water from streams/rivers and groundwater. Rain-fed cultivated-lands in France is almost 90% of its total cultivated area. For Croatia, data given in National Report indicate a 0% of water use for agriculture. The average of water use for agriculture for all the basin is of 62.3% but with a great scatter expressed by a high standard deviation (26.8%) that reflects a wide variation range of water use for agriculture among different countries. The average of water use for agriculture is weakly less on northern countries (52.7%) than on southern countries (75.2) but the twice values are still on the range of the average of the all basin and cannot be taken as indication of difference between north and south. Integrated Water Resources Management (IWRM) plans are currently developed and implemented by various countries to organize the multi-sectoral water uses. On the other hand, the need for Decision Support System (DSS) as a tool in developing and implementing Integrated Water Resources Management (IWRM) is in growing demand. In spite of the great potential for the research and the development of DSS, the utilization of DSS in water management is not widely spread in the partner countries. In some countries, DSS was planned and developed at the scale of territorial integrated water management. Integration of DSS application to the existing IWRM systems at the partner countries would assist in satisfying the water related Millennium Development Goals (MDGs).Integrated Water Resources Management, Decision Support Systems, Mediterranean Basin

Einstein Supergravity and New Twistor String Theories

A family of new twistor string theories is constructed and shown to be free from world-sheet anomalies. The spectra in space-time are calculated and shown to give Einstein supergravities with second order field equations instead of the higher derivative conformal supergravities that arose from earlier twistor strings. The theories include one with the spectrum of N=8 supergravity, another with the spectrum of N=4 supergravity coupled to N=4 super-Yang-Mills, and a family with $N\ge 0$ supersymmetries with the spectra of self-dual supergravity coupled to self-dual super-Yang-Mills. The non-supersymmetric string with N=0 gives self-dual gravity coupled to self-dual Yang-Mills and a scalar. A three-graviton amplitude is calculated for the N=8 and N=4 theories and shown to give a result consistent with the cubic interaction of Einstein supergravity.Comment: LaTeX, 69 pages, no figures; v2: minor corrections made, footnotes and references adde