Six-coordinate organotin(IV) complexes formed using the Kläui ligands; [CpCo{P(OR′)2O}3]SnR3 − nCln

The complexes [CpCo{P(OR′)2O}3]SnR3 − nCln [R′ = Me, Et; R = Ph, Me] are readily prepared from the corresponding organotin chloride and the sodium salt of the Kläui ligands. The X-ray crystal structures of the full series are reported for R = Ph, n = 0-3, and these show that they are all six-coordinate, including the Ph3Sn derivative which is the first example of a SnC3O3 coordination sphere. 1H, 13C, 31P and 119Sn NMR spectra are reported, and interpreted in terms of significant second-order effects and fluxional processes

Novel six-coordinate Aryl- and Alkyltin complexes

Organo-tin compounds have wide applications as pesticides and as intermediates for organic synthesis.¹ They are invariably Sn(IV) derivatives and are generally four-coordinate.² The mixed organo/chioro compounds of the type RnSnCI4-n do however have the ability to expand their coordination numbers to five or six. This depends critically on the substituents - with four organic groups, R₄Sn, there is no tendency at all to coordinate extra ligands, while at the other extreme SnCl₄ readily forms six-coordinate [SnC1₄L₂] complexes since the electronegative halo groups increase the Lewis acidity of the tin centre

Electroweak Theory Without Higgs Bosons

A perturbative SU(2)_L X U(1)_Y electroweak theory containing W, Z, photon, ghost, lepton and quark fields, but no Higgs or other fields, gives masses to W, Z and the non-neutrino fermions by means of an unconventional choice for the unperturbed Lagrangian and a novel method of renormalisation. The renormalisation extends to all orders. The masses emerge on renormalisation to one loop. To one loop the neutrinos are massless, the A -> Z transition drops out of the theory, the d quark is unstable and S-matrix elements are independent of the gauge parameter xi.Comment: 27 pages, LaTex, no figures; revised for publication; accepted by Int. J. Mod. Phys. A; includes biographical note on A. F. Nicholso

Agroindustrialization through institutional innovation

Some small-holders are able to generate reliable and substantial income flows through small-scale dairy production for the local market; for others, a set of unique transactions costs hinders participation. Cooperative selling institutions are potential catalysts for mitigating these costs, stimulating entry into the market, and precipitating growth in rural communities. Trends in cooperative organization in East-African dairy are evaluated. Empirical work focuses on alternative techniques for effecting participation among a representative sample of peri-urban milk producers in the Ethiopian highlands. The techniques considered are a modern production practice (cross-bred cow use), a traditional production practice (indigenous-cow use), three intellectual-capital-forming variables (experience, education, extension), and the provision of infrastructure (as measured by time to transport milk to market). A Tobit analysis of marketable surplus generates precise estimates of non-participants' ‘distances' to market and their reservation levels of the covariates—measures of the inputs necessary to sustain and enhance the market. Policy implications focus on the availability of cross-bred stock and the level of market infrastructure, both of which have marked effects on participation, the velocity of transactions in the local community and, inevitably, the social returns to agroindustrialization.Dairy farming Ethiopia. ,Collective farms Ethiopia. ,

Demographics and viability of an estuarine community of Indo‐Pacific bottlenose dolphins

Wildlife management requires reliable demographic information to assess the status of a population and its vulnerability to threats. This study calculated age class- and sex-specific demographic parameters and assessed the viability of a community of Indo-Pacific bottlenose dolphins (Tursiops aduncus) resident to the Peel-Harvey Estuary in Western Australia. Boat-based photo-identification surveys (n = 483) were conducted between 2016 and 2019. A population viability analysis (PVA) was used to assess the community status and evaluate the effects of adult female and calf mortality, and reproduction on population growth rate. The community comprised 88 (SD = 4.43) individuals with a sex ratio close to parity in all but the adult age class where it was skewed towards females. Demographic changes in this community are driven by births, deaths, and the likely permanent emigration of juvenile males. No immigration was observed. The population is stable (r = −0.004, SD = 0.062) given the current demographic rates. To maintain a community of ~90 individuals, management should consider action to lower adult female and calf mortality. This should involve aiming for zero human caused mortality and ensuring adverse impacts to the population are considered in future development planning

Swift Fox, Vulpes velox, Den Located Next to a Railroad Track in Northwestern Texas

Swift Fox (Vulpes velox) dens are typically found in areas were the vegetation is sparse, in loam soils, and with unobstructed views of the surrounding area. In 2002 a Swift Fox in northwest Texas was found in a unique den situated at the base of a hill with the entrance within 1 m of an active railroad track. Use of a den in such proximity to railroad tracks has never been previously reported

Swift Fox, Vulpes velox, Den Use Patterns in Northwestern Texas

Predator avoidance may be a reason why Swift Foxes (Vulpes velox) are one of the most burrow-dependent canids in North America. Typically Swift Foxes have multiple dens, which they frequently move among. As part of a larger study to reduce Coyote (Canis latrans) related mortalities on Swift Foxes, we installed artificial escape dens in areas occupied by Swift Foxes on Rita Blanca National Grassland, Dallam County, Texas. For this paper, our objective was to determine the effects of artificial escape dens on Swift Fox den use patterns. From January 2002 to August 2004 we captured, radio-collared, and monitored 55 Swift Foxes. We documented annual number of dens used, rate of den use (fidelity), distance between dens, den area, and den sharing. We compared treated (artificial dens installed) and untreated (no artificial dens) areas but found no differences in annual number of dens (P = 0.64; mean = 8), rate of den use (P = 0.96; mean = 35%), mean distance between dens (P = 0.99; mean = 2,311 m), den area (P = 0.55; mean = 5.72 km2), or den sharing (P = 0.46; mean = 42% of time). We did not observe an effect of artificial escape dens on Swift Fox den use patterns probably because artificial escape dens were designed for temporary escape cover rather than diurnal den use

Testing for Features in the Primordial Power Spectrum

Well-known causality arguments show that events occurring during or at the end of inflation, associated with reheating or preheating, could contribute a blue component to the spectrum of primordial curvature perturbations, with the dependence k^3. We explore the possibility that they could be observably large in CMB, LSS, and Lyman-alpha data. We find that a k^3 component with a cutoff at some maximum k can modestly improve the fits (Delta chi^2=2.0, 5.4) of the low multipoles (l ~ 10 - 50) or the second peak (l ~ 540) of the CMB angular spectrum when the three-year WMAP data are used. Moreover, the results from WMAP are consistent with the CBI, ACBAR, 2dFGRS, and SDSS data when they are included in the analysis. Including the SDSS galaxy clustering power spectrum, we find weak positive evidence for the k^3 component at the level of Delta chi' = 2.4, with the caveat that the nonlinear evolution of the power spectrum may not be properly treated in the presence of the k^3 distortion. To investigate the high-k regime, we use the Lyman-alpha forest data (LUQAS, Croft et al., and SDSS Lyman-alpha); here we find evidence at the level Delta chi^2' = 3.8. Considering that there are two additional free parameters in the model, the above results do not give a strong evidence for features; however, they show that surprisingly large bumps are not ruled out. We give constraints on the ratio between the k^3 component and the nearly scale-invariant component, r_3 < 1.5, over the range of wave numbers 0.0023/Mpc < k < 8.2/Mpc. We also discuss theoretical models which could lead to the k^3 effect, including ordinary hybrid inflation and double D-term inflation models. We show that the well-motivated k^3 component is also a good representative of the generic spikelike feature in the primordial perturbation power spectrum.Comment: 23 pages, 6 figures; added new section on theoretical motivation for k^3 term, and discussion of double D-term hybrid inflation models; title changed, added a new section discussing the generic spikelike features, published in IJMP

Surface phase transitions in one-dimensional channels arranged in a triangular cross-sectional structure: Theory and Monte Carlo simulations

Monte Carlo simulations and finite-size scaling analysis have been carried out to study the critical behavior in a submonolayer lattice-gas of interacting monomers adsorbed on one-dimensional channels arranged in a triangular cross-sectional structure. The model mimics a nanoporous environment, where each nanotube or unit cell is represented by a one-dimensional array. Two kinds of lateral interaction energies have been considered: $1)$ $w_L$, interaction energy between nearest-neighbor particles adsorbed along a single channel and $2)$ $w_T$, interaction energy between particles adsorbed across nearest-neighbor channels. For $w_L/w_T=0$ and $w_T > 0$, successive planes are uncorrelated, the system is equivalent to the triangular lattice and the well-known $(\sqrt{3} \times \sqrt{3})$ $[(\sqrt{3} \times \sqrt{3})^*]$ ordered phase is found at low temperatures and a coverage, $\theta$, of 1/3 $[2/3]$. In the more general case ($w_L/w_T \neq 0$ and $w_T > 0$), a competition between interactions along a single channel and a transverse coupling between sites in neighboring channels allows to evolve to a three-dimensional adsorbed layer. Consequently, the $(\sqrt{3} \times \sqrt{3})$ and $(\sqrt{3} \times \sqrt{3})^*$ structures "propagate" along the channels and new ordered phases appear in the adlayer. The Monte Carlo technique was combined with the recently reported Free Energy Minimization Criterion Approach (FEMCA), to predict the critical temperatures of the order-disorder transformation. The excellent qualitative agreement between simulated data and FEMCA results allow us to interpret the physical meaning of the mechanisms underlying the observed transitions.Comment: 24 pages, 6 figure