Capacity and resource allocation of cooperative MIMO in ad hoc networks

Cooperative MIMO (Multiple Input–Multiple Output) allows multiple nodes share their antennas to emulate antenna arrays and transmit or receive cooperatively. It has the ability to increase the capacity for future wireless communication systems and it is particularly suited for ad hoc networks. In this study, based on the transmission procedure of a typical cooperative MIMO system, we first analyze the capacity of single-hop cooperative MIMO systems, and then we derive the optimal resource allocation strategy to maximize the end-to-end capacity in multi-hop cooperative MIMO systems. The study shows three implications. First, only when the intra-cluster channel is better than the inter-cluster channel, cooperative MIMO results in a capacity increment. Second, for a given scenario there is an optimal number of cooperative nodes. For instance, in our study an optimal deployment of three cooperative nodes achieve a capacity increment of 2 bps/Hz when compared with direct transmission. Third, an optimal resource allocation strategy plays a significant role in maximizing end-to-end capacity in multi-hop cooperative MIMO systems. Numerical results show that when optimal resource allocation is applied we achieve more than 20% end-to-end capacity increment in average when compared with an equal resource allocation strategy.

Electronic structure and total energy of interstitial hydrogen in iron: Tight-binding models

An application of the tight binding approximation is presented for the description of electronic structure and interatomic force in magnetic iron, both pure and containing hydrogen impurities. We assess the simple canonical d-band description in comparison to a non orthogonal model including s and d bands. The transferability of our models is tested against known properties including the segregation energies of hydrogen to vacancies and to surfaces of iron. In many cases agreement is remarkably good, opening up the way to quantum mechanical atomistic simulation of the effects of hydrogen on mechanical properties.

The expression and prognostic impact of CXC-chemokines in stage II and III colorectal cancer epithelial and stromal tissue

BACKGROUND: The CXC-chemokine expression is linked with colorectal cancer (CRC) progression but their significance in resected CRC is unclear. We explored the prognostic impact of such expression in stage II and III CRC.

Structural and kinetic studies of spin crossover in an Iron(II) complex with a novel tripodal ligand

Configurational and ligand conformational influences on the kinetics of (1)A(1) reversible arrow T-5(2) spin crossover in the Fe(II) complex with the novel tripodal ligand, 1,1,1-tris((N-(2-pyridylmethyl)-N-methylamino)methyl)ethane (tptMetame), have been explored. Despite having six chelate rings and three chiral nitrogen atoms, only one enantiomeric pair of isomers, Delta, SSS, and Lambda, RRR, of the complex ion is observed. The conformation of the three rings forming the upper ''cap'' of the complex structure can be assigned delta or lambda with respect to the 3-fold molecular axis. X-ray data at 300 and 153 K, above and below the critical temperature for the spin transition, show that the conformation of the ligand ''cap'' is the same as the absolute configuration of the complex, with the same Lambda lambda(CAP)(or Delta delta(CAP)) combination prevailing for both the LS ((1)A(1)) and HS (T-5(2)) isomers. Molecular mechanics calculations further show that the ligand energy remains lowest for this Lambda lambda(CAP) (or Delta delta(CAP)) combination at all Fe-N distances over the range spanning the LS and HS isomers. Measurements of the spin crossover relaxation time have been carried out in solution over the temperature range 293-170 K. The observed monophasic relaxation traces are also consistent with the absolute configuration of the complex remaining unaltered during the spin crossover.

Folklore’s Timeless Past, Ireland’s Present Past, and the Perception of Rural Houses in Early Historic Ireland

This study examines how the archaeology of historic Ireland has been interpreted. Two approaches to the history and archaeology of Ireland are identified. The first, the timeless past, has its roots in a neo-Lamarckian view of the past. This perspective was particularly developed in the work of geographer and ethnographer, Estyn Evans. The second view, associated in particular with a nationalist approach to Ireland’s past, looked to the west of the country where it was believed the culture had been preserved largely unchanged and in its purest form. The continuing impact of these frameworks upon the interpretation of rural settlement in the period 1200– 1700 is examined. It is argued that historians and archaeologists alike have underestimated the quality of buildings.

Complex sociogenetic organization and the origin of unrelated workers in a eusocial sweat bee, Lasioglossum malachurum

Sweat bees (Halictidae) exhibit great interspecific and intraspecific diversity in their social organisation, yet there is remarkably little information on the sociogenetic organisation of any species. Lasioglossum malachurum is a eusocial sweat bee with an annual lifecycle that exhibits considerable variation in its social organisation across its wide geographic range from northern to southern Europe. We collected all adults from 31 L. malachurum nests at Eichkogl, Austria, near the latitudinal centre of its distribution, and genotyped 148 workers using 5 highly variable microsatellite loci developed for this species. Nests were often queenless (48% of nests) during the second phase of worker activity, when colonies were provisioning the sexual brood. Pedigree reconstruction and estimates of nestmate genetic relatedness demonstrated that nests often (32% of nests) contained alien workers, probably as a result of worker drifting from their natal to a foreign nest. Queen effective mating frequency was variable (harmonic mean m(e) = 1.24), but sometimes high (maximum 2.7). These data demonstrate that nests of L. malachurum do not have a classical eusocial sociogenetic organisation (monogyny, monandry) and thereby pose a challenge to exclusively relatedness based arguments for the evolution of eusociality in the taxon.