Study in Royal Society journal on how relationship status influences sex ratios

10/18/04

Weekly roundup of papers published in Royal Society journals

Proceedings of The Royal Society B: Biological Sciences

Partnership status and the human sex ratio at birth by Dr K Norberg
Could the sex of a child be influenced by the status of the parents' relationship at the time of conception? In a sample of 86,436 births in the United States, I find a small excess of sons among births to parents who were married or living with an opposite sex partner before the child's conception, compared to births to parents who were not. This is the first evidence that household arrangements can affect the human sex ratio at birth, and could explain the fall in the proportion of male births in some developed countries over the past thirty years. Contact: Dr Karen Norberg, National Bureau of Economic Research, 1050 Massachusetts Avenue, CAMBRIDGE, MA 02138, USA

Obtaining multiple separate food sources: behavioural intelligence in the Physarum plasmodium by Dr T Nakagaki, Dr R Kobayashi, Dr Y Nishiura and Dr T Ueda
In order to evaluate an amoeba's performance in a complex survival task, we studied the morphology of the Physarum plasmodium transportation network when presented with multiple separate food sources. The plasmodium comprises a network of tubular elements through which chemical nutrient, intracellular signals and the viscous body are transported and circulated. We report the evidence that the tube network is reformed as well-designed with short total length and fault tolerance, in response to locations of food sources. This implies that this unicellular organism has high computational ability to solve some optimization problem, difficult even for human. Contact: Dr Toshiyuki Nakagaki, Research Institute for Electronic Science, Hokkaido University, SAPPORO, 060-0812, Japan

Proceedings of The Royal Society A: Mathematical, Physical and Engineering Sciences

Distillation of secret key and entanglement from quantum states by Dr I Devetak and Dr A Winter
Sharing a secret with someone else means two things; first, to be perfectly correlated (you have to agree on the information); second, to be perfectly decorrelated from your enemy, the eavesdropper. Neither of these conditions implies the other, as easy examples show. But only in a classical world: quantum mechanical correlations, if they achieve maximal strength (what is called entanglement), are secret automatically. This "monogamous" nature of entanglement has been used to guarantee the security of quantum cryptography. In this paper the reasoning is reversed: it is shown how to make secrets directly from first principles, and then how to turn the process into a quantum entanglement generating one. This is very interesting, as entanglement is the key resource in the emerging technology of quantum information processing. Also, it means that the exotic quantum entanglement is not too far conceptually from secret sharing. Amazingly, we can in this way prove one of the big open questions in entanglement theory, the "hashing inequality". Contact: Dr Andreas Winter, Department of Computer Science, University of Bristol, Merchant Ventures Building, Woodland Road, BRISTOL, BS8 1UB

Phase mixing of Alfvn pulses and wavetrains propagating in coronal holes by Professor AW Hood, Dr SJ Brooks and Dr AN Wright The atmosphere of the Sun is incredibly hot (a few million degrees centigrade) and permeated by magnetic field lines emerging from the much cooler solar surface. There is considerable debate among scientists over the process by which the atmosphere is heated. In this article we investigate one of the more likely heating mechanisms: Movement of the solar surface sends waves travelling along the magnetic field lines (like waves on a slinky spring). We find that these waves can be converted to heat quite efficiently and are likely to be important for heating the solar atmosphere. Contact: Professor Alan Hood, School of Mathematics and Statistics, University of St Andrews, North Haugh, St Andrews, FIFE, KY16 9SS

Geodesic and re-coupling-induced limits to S2n group invariants of uniform (k1 k2n) dual tensorial sets in spin physics, or NMR: SR dynamical structure on {Hv} via polyhedral re-coupling and time-reversal invariance Additional compaction of SI cardinalities is observed via mappings based on (Lie) "group measures over isomorphic algebra(s)", e.g. for [AX]n NMR total SI-cardinalities. Conventional Jucy recoupling and Weyl/Corio NMR SI/xDj(U)(SU2)/ theory is now seen as being restricted to at-most "Abelian" spin systems. Further, the value of the present polyhedral lattice point of view of democratic recoupling is that it stresses the precise role of topological geometry in Sn group properties. These define the degenerate NMR spin system "dynamical structure" and their "uniform" dual tensorial set completeness via TRI-invariance and its combinatorics. Contact: Dr Francis Temme, Department of Chemistry, Queen's University, Kingston, ONTARIO, K7L 3N6, Canada

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