Chiral mixed phase in disordered 3d Heisenberg models

Using Monte Carlo simulations, we compute the spin stiffness of a site-random 3d Heisenberg model with competing ferromagnetic and antiferromagnetic interactions. Our results for the pure limit yield values of the the critical temperature and the critical exponent $\nu$ in excellent agreement with previous high precision studies. In the disordered case, a mixed "chiral" phase is found which may be in the same universality class as 3d Heisenberg spin glasses.Comment: 5 pages, 4 figures, accepted in PRB Rapid Communication

Critical properties of a continuous family of XY noncollinear magnets

Monte Carlo methods are used to study a family of three dimensional XY frustrated models interpolating continuously between the stacked triangular antiferromagnets and a variant of this model for which a local rigidity constraint is imposed. Our study leads us to conclude that generically weak first order behavior occurs in this family of models in agreement with a recent nonperturbative renormalization group description of frustrated magnets.Comment: 5 pages, 3 figures, minor changes, published versio

Security on Medical Wireless Sensor Networks

Wireless technology is fast becoming a very important tool for all aspects of communication. An area that lacks a strong implementation for wireless communication is the medical field. Wireless systems could be used by clinicians to be better able to diagnose and monitor patients. The reason behind the lack of adoption in healthcare is due to the need to meet the legislated and perceived requirements of security and privacy when dealing with clinical information. The current methods of wireless authentication are investigated and an existing issue in mobile networks is described and solved with two novel solutions; one solution within GSM and the other within UMTS. Strong authentication protocols are developed based on the existing wireless protocols, while using minimal messages and symmetric operations to limit resource utilization to meet the needs of the healthcare environment. To ensure the quality of the protocol a BAN (Burrows-Abadi-Needham logic) analysis is performed which verifies that the desired goals of the protocols are appropriately met within the results analysis. The developed security protocol is shown to be secure, uses minimal messages to maintain efficiency and meets the legal requirements to be used in medical wireless sensor networks

Government-University Relations: 1MB or No 1MB? A Comparative View of Alberta and British Columbia

The concept of an intermediary body (1MB) between government and universities has often been debated in the literature of higher education in Canada. While much of the discussion has centred around the theoretical advantages for both organizations which would accrue from the establishment of an 1MB, there have been few attempts to assess whether these advantages occur in practice. This paper reports on the result of a study of government - university relations in Alberta and British Columbia. The major purpose was to analyse differences in matters of autonomy, budget allocation, and planning, existing between Alberta, which abolished its 1MB in 1972, and British Columbia, which has had a Universities Council since 1974. The results indicated very few differences between the two provinces in the matters under review. What did emerge, however, were some important requirements for the effective operation of universities during the financial realities of the eighties.L'on a souvent discuté dans la littérature couvrant l'éducation tertiaire au Canada la question d'une agence intermédiaire entre le gouvernement et les universités. La plupart de ces discussions traitent des avantages théoriques pour les deux groupes dérivant de Vétablissement d'une telle agence. Il y a eu, par contre, peu d'études faites sur la façon dont ces avantages se manifestent dans la pratique. Le présent article décrit une étude faite sur les relations entre le gouvernement et les universités en Alberta et en Colombie Britannique: il analyse les différences d'autonomie, d'allocation budgétaire, et de planning qui existent entre l'Alberta, où l'agence intermédiaire a été abolie en 1972, et la Colombie Britannique, où un Conseil des Universités existe depuis 1974. Les résultats indiquent très peu de différence entre les deux provinces sur les questions couvertes par la présente enquête. Par contre, l'étude démontre qu'il existe d'importants critères nécessaires à l'opération efficace des universités pour faire face aux réalités financiaires des années quatre-vingt

Electrochemically directed synthesis of oligonucleotides for DNA microarray fabrication

We demonstrate a new method for making oligonucleotide microarrays by synthesis in situ. The method uses conventional DNA synthesis chemistry with an electrochemical deblocking step. Acid is delivered to specific regions on a glass slide, thus allowing nucleotide addition only at chosen sites. The acid is produced by electrochemical oxidation controlled by an array of independent microelectrodes. Deblocking is complete in a few seconds, when competing side-product reactions are minimal. We demonstrate the successful synthesis of 17mers and discrimination of single base pair mismatched hybrids. Features generated in this study are 40 μm wide, with sharply defined edges. The synthetic technique may be applicable to fabrication of other molecular arrays

Z_2-vortex ordering of the triangular-lattice Heisenberg antiferromagnet

Ordering of the classical Heisenberg antiferromagnet on the triangular lattice is studied by means of a mean-field calculation, a scaling argument and a Monte Carlo simulation, with special attention to its vortex degree of freedom. The model exhibits a thermodynamic transition driven by the Z_2-vortex binding-unbinding, at which various thermodynamic quantities exhibit an essential singularity. The low-temperature state is a "spin-gel" state with a long but finite spin correlation length where the ergodicity is broken topologically. Implications to recent experiments on triangular-lattice Heisenberg antiferromagnets are discussed

Platform Competition: The Role of Multi-homing and Complementors

In this paper we present a model of platform competition in which two firms offer horizontally differentiated platforms and a group of complementors offers products that are complementary to each platform. Consumers can buy either or both platforms (single- or multihoming) and complementors can produce for either or both platforms (single- or multi-production). We first characterize the pricing structure and find that, in equilibrium, consumers are more likely to multihome as the differentiation of platforms decreases or as the number of complementors for either platform increases. We show that the platform and its complementors always benefit from an increase in the number of complementors in their own platform. When single-homing arises in equilibrium, the platform and its complementors suffer from an increase in the number of complementors in the rival platform. We also study the incentives of the platform to integrate with its complementors, to charge them a royalty or give a subsidy, and to sell its own complementary products to the rival platform

Glycine supplementation to low protein, amino acid-supplemented diets supports optimal performance of broiler chicks

Six experiments were conducted to determine the effects of low CP in diets for broilers and to evaluate limiting essential and nonessential amino acids (AA) in these diets. All experiments were conducted with Ross x Ross broilers in brooder batteries from 0 to 17 or 18 d posthatch. Treatments were replicated with 6 pens of either 5 or 6 broilers each. In Experiment (Exp.) 1, corn-soybean meal diets were formulated to 16.18, 17.68, 19.18, 20.68, or 22.18% CP. The 22.18% CP diet provided 1.23% Lys and 0.89% TSAA, met or exceeded all nutrient requirements of young broilers, and served as the positive control (PC) diet in all experiments. Increasing dietary CP linearly increased final BW, daily gain (ADG), and gain:feed (G:F) (P \u3c 0.005). In Exp. 2, additions of crystalline essential (EAA) or nonessential AA (NEAA) were added to the low CP diet to simulate the AA profile of the PC. Daily gain, final BW, and G:F were decreased (P \u3c 0.01) when CP was reduced, but the addition of the NEAA increased final BW, ADG, and G:F (P \u3c 0.07) to the level of broilers fed the PC. Addition of EAA alone was without effect. In Exp. 3, chicks fed diets with supplemental Glu, Ala, Asp, or Pro had reduced daily feed intake (ADFI), ADG, and final BW (P \u3c 0.05) compared with the PC diet. Addition of Gly or the combination of Gly, Glu, Asp, Ala, and Pro to the low CP diet increased G:F (P \u3c 0.01) compared with chicks fed PC, and ADG was not different from that of broilers fed the PC diet. In Exp. 4, chicks were fed either the PC diet, the low CP diet with Gly + Ser concentrations of 1.23, 1.35, 1.47, 1.59, 1.71, 1.83, 1.95, or 2.07%, or a 10th diet that contained 1.23% Gly + Ser and with Glu to equal the N concentration of the 2.07% Gly + Ser diet. Final BW, ADG, and G:F were increased linearly (P \u3c 0.001) as the concentration of dietary Gly + Ser was increased. Chicks fed the low CP diet with 2.07% Gly + Ser had growth performance that was not different from that of chicks fed the PC. The addition of Glu to the low CP diet was without effect. In Exp. 5, chicks were fed the PC with additions of 0, 0.15, or 0.30% Gly or the low CP diet containing 1.60, 1.72, 1.84, 1.96, 2.08, 2.20, or 2.32% Gly + Ser. Glycine addition to the PC had no effect, but Gly addition to the low CP diet increased G:F linearly (P \u3c 0.001). Growth performance of chicks fed the low CP diet with 2.32% Gly + Ser was equal to that of chicks fed the PC diet. In Exp. 6, chicks were fed the PC or the low CP diet containing 1.80, 1.95, 2.10, 2.25, 2.40, 2.55, 2.70, 2.85, or 3.00% Gly + Ser. Glycine addition to the low CP diet increased G:F linearly (P \u3c 0.001). In summary, low CP diets result in optimal growth of broilers with Gly + Ser levels of 2.44%. ©2006 Poultry Science Association, Inc

Monte Carlo Study of the Anisotropic Heisenberg Antiferromagnet on the Triangular Lattice

We report a Monte Carlo study of the classical antiferromagnetic Heisenberg model with easy axis anisotropy on the triangular lattice. Both the free energy cost for long wavelength spin waves as well as for the formation of free vortices are obtained from the spin stiffness and vorticity modulus respectively. Evidence for two distinct Kosterlitz-Thouless types of defect-mediated phase transitions at finite temperatures is presented.Comment: 8 pages, 10 figure