Spin liquid phase in a spatially anisotropic frustrated antiferromagnet

We explore the effect of the third nearest-neighbors on the magnetic properties of the Heisenberg model on an anisotropic triangular lattice. We obtain the phase diagram of the model using Schwinger-boson mean-field theory. Competition between N\'eel, spiral and collinear magnetically ordered phases is found as we vary the on the ratios of the nearest, J1, next-nearest, J2, and third-nearest, J_3, neighbor exchange couplings. A spin liquid phase is stabilized between the spiral and collinear ordered states when J2/J1 < 1.8 for rather small J3/J1 < 0.1. The lowest energy two-spinon dispersions relevant to neutron scattering experiments are analyzed and compared to semiclassical magnon dispersions finding significant differences in the spiral and collinear phases between the two approaches. The results are discussed in the context of the anisotropic triangular materials: Cs2CuCl4 and Cs2CuBr4 and layered organic materials, kappa-(BEDT-TTF)2X and Y[Pd(dmit)2]2.Comment: 11 pages, 9 figure

Spin liquid phase due to competing classical orders in the semiclassical theory of the Heisenberg model with ring exchange on an anisotropic triangular lattice

Linear spin wave theory shows that ring exchange induces a quantum disordered region in the phase diagram of the title model. Spin wave spectra show that this is a direct manifestation of competing classical orders. A spin liquid is found in the `Goldilocks zone' of frustration, where the quantum fluctuations are large enough to cause strong competition between different classical orderings but not strong enough to stabilize spiral order. We note that the spin liquid phases of $\kappa$-(BEDT-TTF)${_2}X$ and $Y$[Pd(dmit)$_2$]$_2$ are found in this Goldilocks zone.Comment: 5 pages, 3 figure

A Simple Mixture Theory for ν Newtonian and Generalized Newtonian Constituents

This work presents development of mathematical models based on conservation laws for a saturated mixture of ν homogeneous, isotropic, and incompressible constituents for isothermal flows. The constituents and the mixture are assumed to be Newtonian or gen- eralized Newtonian fluids. Power law and Carreau-Yasuda models are considered for gen- eralized Newtonian shear thinning fluids. The mathematical model is derived for a ν con- stituent mixture with volume fractions φα using principles of continuum mechanics: con- servation of mass, balance of momenta, first and second laws of thermodynamics, and principles of mixture theory yielding continuity equations, momentum equations, energy equation, and constitutive theories for mechanical pressures and deviatoric Cauchy stress tensors in terms of the dependent variables related to the constituents. It is shown that for Newtonian fluids with constant transport properties, the mathematical models for con- stituents are decoupled. In this case one could use individual constituent models to obtain constituent deformation fields, and then use mixture theory to obtain the deformation field for the mixture. In the case of generalized Newtonian fluids, the dependence of viscosities on deformation field does not permit decoupling. Numerical studies are also presented to demonstrate this aspect. Using fully developed flow of Newtonian and generalized Newto- nian fluids between parallel plates as a model problem, it is shown that partial pressures pα of the constituents must be expressed in terms of the mixture pressure p. In this work we propose pα = φα p and ν α pα = p which implies ν α φα = 1 which obviously holds. This rule for partial pressure is shown to be valid for a mixture of Newtonian and generalized Newtonian constituents yielding Newtonian and generalized Newtonian mixture. Modifi- cations of the currently used constitutive theories for deviatoric Cauchy stress tensor are proposed. These modifications are demonstrated to be essential in order for the mixture theory for ν constituents to yield a valid mathematical model when the constituents are the same. Dimensionless form of the mathematical models are derived and used to present numerical studies for boundary value problems using finite element processes based on a residual functional i.e. least squares finite element processes in which local approximations are considered in H k,p Ωe scalar product spaces. Fully developed flow between parallel plates and 1:2 asymmetric backward facing step are used as model problems for a mixture of two constituents

The Remediation of School Psychologist Trainees

School Psychology training programs have an important responsibility of making sure their graduates are competent professionals. The current study gathered data from National Association of School Psychologists (NASP) approved training programs in order to explore how they have handled competency problems in their program. A survey was sent to all NASP approved training programs via e-mail. Surveys were also completed by 32 program representatives at the 2010 Annual NASP Conference. The results of the survey were analyzed using Chi Square and a frequency analysis. The Chi Square analysis did not yield any significant differences at p\u3c0.05 between educational specialist or equivalent degree programs and doctorate degree programs. The frequency analysis, however, did disclose pertinent data in regards to the remediation of school psychology trainees

A note on the use of FTA™ technology for storage of blood samples for DNA analysis and removal of PCR inhibitors

peer-reviewedFTA™ technology is widely used across many molecular disciplines for sample capture, storage and analysis. The use of this technology for the long-term storage of blood samples for DNA analysis was examined as well as its potential to remove inhibitors from DNA samples previously extracted from blood with PCR inhibitors remaining. It was found that blood spots stored on FTA™ cards for 8 years at room temperature gave successful PCR products and that FTA™ cards are a useful tool for removing substances in samples which interfere with or inhibit, the PCR reaction

Studies in isoquinoline chemistry relating to morphine analgesics

Approaches to the synthesis of partially hydrogenated 8-ketoisoquinolines have been made via 5,6,7,8-tetrahydroisoquinoline and also via attempted Bischler–Napieralski cyclodehydration of a series of 3-oxygenated cyclohexenyl-phenylacetamide derivatives. This latter ring closure has been found not to take, place and the former route also did not prove satisfactory. The synthesis of ring-A bridged isoquinolines has been studied. Although thermal isomerisation of 2,5-dihydrophenylacetamides to give conjugated dienes followed by Diels–Alder reaction met with limited success, the Diels–Alder reaction of 1,2,3,4,7,8-hexahydro-6-methoxy-2-methylisoquinoline has been achieved with methyl vinyl ketone, phenyl vinyl ketone and 2-chloroacrylonitrile. The exo- and endo-cycloadducts have been separated by column- and thin-layer chromatography and their stereochemistry assigned on the basis of n.m.r. studies. [Continues.

A Stochastic Salvo Model Analysis of the Battle of the Coral Sea

In this work we study the Battle of the Coral Sea using a stochastic version of the salvo combat model. We begin by estimating the range of probable alternative results for the battle, given the forces employed; i.e., if the battle were to be "re-fought", how likely are outcomes other than what historically transpired? Our analysis suggests that a wide range of results was indeed possible, even without any change in forces on either side. We then estimate the impact of hypothetical but plausible changes in the American forces employed. Our analysis suggests that a material advantage could have been obtained by committing extra aircraft carriers to the battle or by dispersing the carriers that were already deployed; on the other hand, equipping each carrier with more fighters but fewer bombers would have yielded a net disadvantage.Natural Sciences and Engineering Research Council (NSERC) Discovery Grant; Carleton University Centre for Security & Defense Studies

Investigation of Prolific Sheep from UK and Ireland for Evidence on Origin of the Mutations in BMP15 (FecXG, FecXB) and GDF9 (FecGH) in Belclare and Cambridge Sheep

peer-reviewedThis paper concerns the likely origin of three mutations with large effects on ovulation rate identified in the Belclare and Cambridge sheep breeds; two in the BMP15 gene (FecXG and FecXB) and the third (FecGH) in GDF9. All three mutations segregate in Belclare sheep while one, FecXB, has not been found in the Cambridge. Both Belclare and Cambridge breeds are relatively recently developed composites that have common ancestry through the use of genetic material from the Finnish Landrace and Lleyn breeds. The development of both composites also involved major contributions from exceptionally prolific ewes screened from flocks in Ireland (Belclare) and Britain (Cambridge) during the 1960s. The objective of the current study was to establish the likely origin of the mutations (FecXG, FecXB and FecGH) through analysis of DNA from Finnish Landrace and Lleyn sheep, and Galway and Texel breeds which contributed to the development of the Belclare breed. Ewes with exceptionally high prolificacy (hyper-prolific ewes) in current flocks on Irish farms were identified to simulate the screening of ewes from Irish flocks in the 1960s. DNA was obtained from: prolific ewes in extant flocks of Lleyn sheep (n = 44) on the Lleyn peninsula in Wales; hyper-prolific ewes (n = 41); prolific Galway (n = 41) ewes; Finnish Landrace (n = 124) and Texel (n = 19) ewes. The FecXG mutation was identified in Lleyn but not in Finnish Landrace, Galway or Texel sheep; FecXB was only found among the hyper-prolific ewes. The FecGH mutation was identified in the sample of Lleyn sheep. It was concluded from these findings that the Lleyn breed was the most likely source of the FecXG and FecGH mutations in Belclare and Cambridge sheep and that the FecXB mutation came from the High Fertility line that was developed using prolific ewes selected from commercial flocks in Ireland in the 1960′s and subsequently used in the genesis of the Belclare.Financial support through the Teagasc Walsh Fellowship Scheme, Genesis Faraday SPARK award (Lleyn survey) and Science Foundation Ireland (07/SRC/B1156) is gratefully acknowledged