Preferred Alignment Research Articles

Pn Tomographic Velocity and Anisotropy beneath the Iran Region

We present tomographic velocity and anisotropy models of the uppermost mantle beneath the Iran region. A total of 74,375 Pn phase readings from 86 stations of the Iranian network and 133 stations of the International Seismological Centre are used in the investigation. The study uses the Pn travel‐time tomography method proposed by Hearn (1996). The tomography results show some interesting anomalies. The average Pn velocity under the Iran region is approximately 8.0 km/s, and the maximum velocity perturbations are approximately 3%–4%. High Pn velocities under the Zagros Mountains and the Caspian Sea may be due to the presence of oceanic crust/lithosphere material. Low Pn velocities were found under the Alborz and Caucasus regions and may be due to higher temperatures or partial melting resulting from volcanoes and mid‐Cenozoic volcanic/plutonic rocks in these regions. The inversion velocities support the idea that the subduction of the Arabian plate into the mantle beneath the Iranian plateau may have resulted in the upwelling of hot material. The well‐resolved Pn anisotropy model is jointly obtained with a velocity model for the areas with good ray‐path coverage. In the plate collision regions (Zagros and Alborz), the fast Pn anisotropy direction is oriented parallel to the collision arc and to large reverse faults due to pure shear deformation from cross‐fault compression and along‐fault extension. Under the Caucasus regions, the Pn anisotropy results indicate that the preferred alignment of olivine crystals is parallel to the plate movement direction; however, the surface fault strike is at an angle of nearly 45° with the crustal movement direction and anisotropy. These differing deformations suggest potential decoupling between the crust and upper mantle. The possible decoupling and differing deformation between the crust and upper mantle are easily enhanced under high temperatures due to volcanoes and supported by low velocities beneath the Caucasus. We validate the existence of Pn anisotropy under these regions by azimuthal averaging of the apparent Pn velocity.

Topographic cues of nano‐scale height direct neuronal growth pattern

We study the role of nano-scale cues in controlling neuronal growth. We use photolithography to fabricate substrates with repeatable line-pattern ridges of nano-scale heights. We find that neuronal processes, which are of micron size, have strong interactions with ridges even as low as 10 nm. The interaction between the neuronal process and the ridge leads to a deflection of growth direction and a preferred alignment with the ridges. The interaction strength clearly depends on the ridges' height. For 25 nm ridges approximately half of the neuronal processes are modified, while at 100 nm the majority of neurites change their original growth direction post interaction. In addition, the effect on growth correlates with the incoming angle between the neuronal process and the ridge. We underline the adhesion as a key mechanism in directing neuronal growth. Our study highlights the sensitivity of growing neurites to nano-scale cues thus opens a new avenue of research for pre-designed neuronal growth and circuitry.

Stability and Preference Alignment in Matching and Coalition Formation

We study matching and coalition formation environments allowing complementarities and peer effects. Agents have preferences over coalitions, and these preferences vary with an underlying, and commonly known, state of nature. Assuming that there is substantial variability of preferences across states of nature, we show that there exists a core stable coalition structure in every state if and only if agents' preferences are pairwise‐aligned in every state. This implies that there is a stable coalition structure if agents' preferences are generated by Nash bargaining over coalitional outputs. We further show that all stability‐inducing rules for sharing outputs can be represented by a profile of agents' bargaining functions and that agents match assortatively with respect to these bargaining functions. This framework allows us to show how complementarities and peer effects overturn well known comparative statics of many‐to‐one matching.

Hanging Together or Being Hung Separately: The Strategic Power of Coalitions where Bargaining Occurs with Incomplete Information

What is the strategic role of membership in an intergovernmental group with unanimity requirements if the group negotiates with an external player in a setting with incomplete information? Being in such a group has a strategic effect compared to negotiating as a stand-alone player and reduces the demands of the outside player: being in a group lends additional bargaining power. Negotiating as a group may also cause more inefficiencies due to bargaining failure, and this may harm also the intergovernmental group. We uncover the role of preference alignment and preference independence between members of the coalition group for equilibrium payoffs and welfare effects. In this analysis we also distinguishing between coalition groups with and without side payments. Overall, coalition groups tend to perform well for the members of the coalition group in comparison to fully decentralized negotiations, particularly if the objectives of the members of the coalition group are not always perfectly aligned.

Determination of the layer-specific distributed collagen fibre orientations in human thoracic and abdominal aortas and common iliac arteries

The established method of polarized microscopy in combination with a universal stage is used to determine the layer-specific distributed collagen fibre orientations in 11 human non-atherosclerotic thoracic and abdominal aortas and common iliac arteries (63 ± 15.3 years, mean ± s.d.). A dispersion model is used to quantify over 37 000 recorded fibre angles from tissue samples. The study resulted in distinct fibre families, fibre directions, dispersion and thickness data for each layer and all vessels investigated. Two fibre families were present for the intima, media and adventitia in the aortas, with often a third and sometimes a fourth family in the intima in the respective axial and circumferential directions. In all aortas, the two families were almost symmetrically arranged with respect to the cylinder axis, closer to the axial direction in the adventitia, closer to the circumferential direction in the media and in between in the intima. The same trend was found for the intima and adventitia of the common iliac arteries; however, there was only one preferred fibre alignment present in the media. In all locations and layers, the observed fibre orientations were always in the tangential plane of the walls, with no radial components and very small dispersion through the wall thickness. A wider range of in-plane fibre orientations was present in the intima than in the media and adventitia. The mean total wall thickness for the aortas and the common iliac artery was 1.39 and 1.05 mm, respectively. For the aortas, a slight thickening of the intima and a thinning of the media in increasingly distal regions were observed. A clear intimal thickening was present distal to the branching of the celiac arteries. All data, except for the media of the common iliac arteries, showed two prominent collagen fibre families for all layers so that two-fibre family models seem most appropriate.

Relaxation mechanisms in magnetic colloids studied by stroboscopic spin-polarized small-angle neutron scattering

Stroboscopic small-angle neutron scattering by using polarized neutrons is presented as a technique for investigations of relaxation phenomena on a nanometer scale. Applying a cyclic perturbation to the sample by an oscillating magnetic field allows the polarization-dependent scattering cross-sections to be extracted as time-dependent response. The potential of this special type of ``physical'' contrast variation technique is demonstrated with three examples of ferrofluids of different particle sizes and viscosities. The dynamics of magnetic moment reorientations turned out to be governed by different time scales. For a temperature-dependent fraction of individual mobile particles, a frequency-dependent phase shift and damping of the intensity modulation have been precisely determined and quantitatively explained using a Debye-like relaxation model. The characteristic relaxation times, \ensuremath{\tau}, in the liquid state of all samples scale with the particle volume and viscosity confirming a Brownian-relaxation mechanism. For the remaining fraction of particles that form locally ordered domains the orientation distribution of the dynamically arrested static moments has been quantified by an order parameter ${S}_{1}$${}^{\mathrm{arr}}$, which is not accessible with nonpolarized neutrons. In a high viscous Co and a magnetite-based ferrofluid, ${S}_{1}$${}^{\mathrm{arr}}$ corresponds to maximal alignment of the static moments in the liquid state and to a gradual decrease at lower temperatures when the solvent is frozen. In a low viscosity Co-ferrofluid almost no preferred alignment of the arrested particle moments was observed. In the magnetite-based ferrofluid with the highest dipolar attraction energy an additional phase shift has been detected which increases with frequency and magnitude of the magnetic field. This indicates clearly that the set-up of local particle ordering in distorted hexagonal arrangement is delayed with respect to the moment alignment in the time varying magnetic field.

Directional Anisotropy in the Mechanical Behavior of Friction Stir Processed and Aged AZ91 Alloy

Friction stir processing (FSP) is an emerging grain refinement technique for magnesium alloys. In this study, a cast AZ91 alloy was processed by a single-pass FSP to achieve an average grain size of ~6 mm in the nugget zone. The FSP is found to introduce texture in the alloy due to preferred alignment of basal poles in the processing direction. The mechanical behavior is significantly influenced by texture. After FSP, the alloy was aged at different temperatures and times for continuous and discontinuous precipitation of b-Mg17Al12. A high anisotropy in yield stress is observed in the processing and transverse direction after FSP. It is shown that this anisotropy can be minimized under optimum ageing conditions. The observed yield asymmetry is correlated with the texture variation after FSP. The role of b-Mg17Al12 precipitates in reducing the yield anisotropy is also discussed.

Forces on a Small Grain in the Nonlinear Plasma Wake of Another

The transverse force on a spherical charged grain lying in the plasma wake of another grain is analyzed to assess the importance of ion-drag perturbation, in addition to the wake-potential-gradient. The ion-drag perturbation is intrinsically one order smaller than the wake-potential force in the ratio of grain size (r(p)) to Debye length (λ(De)). So ion-drag perturbation is important only in nonlinear wakes. Rigorous particle-in-cell calculations of the force are performed in the nonlinear regime with two interacting grains. It is found that even for quite large grains, r(p)/λ(De)=0.1, the force is dominated by the wake-potential gradient. The wake-potential structure can then help explain the preferred alignment of floating dust grains.

Authority, Consensus and Governance

We look for necessary properties of shareholder-value maximizing corporate boards when shareholders face a trade-off between improving information sharing between the board and management and reducing distortions in decision-making arising out of managerial agency. We draw a distinction between the alignment of preferences of the board with management (which affects information flows) and the allocation of authority to the board or management (which affects ex-post decisions). We show that it is in general suboptimal to allocate authority to management. Authority should be held by a supervisory board that may be imperfectly aligned with both shareholders and management. Indeed, even when management has captured all authority and the board only has an advisory role, the optimal board may be designed to withhold information from management. An optimal advisory board must however be sufficiently aligned with management in order to create ex-post consensus and ensure authority is irrelevant. Given optimal board alignment, the value of the board's authority equals the cost of requiring consensus. Shareholders may hold ultimate decision-making authority within an optimal supervisory board without any loss in welfare and in many cases this is strictly optimal.

Principal stiffness orientation and degree of anisotropy of human osteons based on nanoindentation in three distinct planes

Haversian systems or ‘osteons’ are cylindrical structures, formed by bone lamellae, that make up the major part of human cortical bone. Despite their discovery centuries ago in 1691 by Clopton Havers, their mechanical properties are still poorly understood.The objective of this study is a detailed identification of the anisotropic elastic properties of the secondary osteon in the lamella plane. Additionally, the principal material orientation with respect to the osteon is assessed. Therefore a new nanoindentation method was developed which allows the measurement of indentation data in three distinct planes on a single osteon.All investigated osteons appeared to be anisotropic with a preferred stiffness alignment along the axial direction with a small average helical winding around the osteon axis. The mean degree of anisotropy was 1.75 ± 0.36 and the mean helix angle was 10.3°±0.8°.These findings oppose two well established views of compact bone microstructure: first, the generally clear axial stiffness orientation contradicts a regular ‘twisted plywood’ collagen fibril orientation pattern in lamellar bone that would lead to a more isotropic behavior. Second, the class of transverse osteons were not observed from the mechanical point of view.

Generalized Lemaître-Tolman-Bondi model with inhomogeneous isotropic dark energy: Observational constraints

We consider on-center and off-center observers in an inhomogeneous, spherically symmetric, isocurvature (flat) concentration of dark energy with a typical size of a few Gpc. Such a concentration could be produced e.g. by a recently formed global monopole with core size that approaches the Hubble scale. In this case we would have what may be called ``topological quintessence'' in analogy with the well-known topological inflation. We show that the minimum comoving radius ${r}_{0\mathrm{min}}$ of such a dark energy inhomogeneity that is consistent with the Union2 type Ia supernovae data at the $3\ensuremath{\sigma}$ level is ${r}_{0\mathrm{min}}\ensuremath{\simeq}1.8\text{ }\text{ }\mathrm{Gpc}$. As expected, the best-fit fractional dark energy density at the center, ${\ensuremath{\Omega}}_{X,\mathrm{in}}$, approaches the corresponding $\ensuremath{\Lambda}\mathrm{CDM}$ value ${\ensuremath{\Omega}}_{X,\mathrm{in}}=0.73$ for large enough values of the inhomogeneity radius ${r}_{0}$ (${r}_{0}>4\text{ }\text{ }\mathrm{Gpc}$). Using the Union2 data, we show that the maximum allowed shift ${r}_{\mathrm{obs}\mathrm{\text{\ensuremath{-}}}\mathrm{max}}$ of the observer from the center of the inhomogeneity is about $0.7{r}_{0}$, which respects the Copernican principle. The model naturally predicts the existence of a preferred axis and alignment of the low CMB multipoles. However, the constraints on ${r}_{\mathrm{obs}\mathrm{\text{\ensuremath{-}}}\mathrm{max}}$ coming from the magnitude of the CMB dipole remain a severe challenge to the Copernican principle and lead to ${r}_{\mathrm{obs}\mathrm{\text{\ensuremath{-}}}\mathrm{max}}<110\text{ }\text{ }\mathrm{Mpc}$, even for an inhomogeneity radius as large as ${r}_{0}=7\text{ }\text{ }\mathrm{Gpc}$.

Anisotropy as cause for polarity reversals of D″ reflections

Recordings of seismic events that sample the deep mantle can test different hypotheses of mantle processes and composition. Seismic reflections from structures in the D″ region — the bottom 200–400 km of the Earth's mantle — can provide information on the velocity contrasts in this region. By studying the waveforms and polarities of the D″ reflections in P and S-waves, we can potentially distinguish between different explanations for the observed structures, such as phase transitions, mineral texture or thermal anomalies. Here we use source–receiver combinations that contain reflections from D″ in two different regions that are both characterised by fast seismic velocities in tomographic models. Beneath the Caribbean a positive S-velocity contrast but negative P-wave velocity contrast across the D″ reflector has been reported previously, consistent with a model of a phase change in MgSiO 3. In the second fast velocity region (Eurasia) we detect positive P- and S-wave velocity contrasts in two orthogonal paths crossing in the lowermost mantle indicating a different scenario for D″. A path that crosses this region in 45° to the other two great circle paths shows evidence for a negative P velocity contrast. One explanation to reconcile observations in both regions is a phase transition from perovskite to post-perovskite with a fraction of 12% preferred crystal alignment in the post-perovskite phase. Depending on the travel direction of the waves with respect to the flow direction in the lower mantle, positive or negative velocity jumps can be expected. Other anisotropic models are considered but cannot fully explain the range of observations we find in the data.

The phylogeny of monkey beetles based on mitochondrial and ribosomal RNA genes (Coleoptera: Scarabaeidae: Hopliini)

Monkey beetles (Hopliini) are a large clade of flower and leaf feeding species within the Scarabaeidae (chafers) with greatest diversity in southern Africa. Their internal relationships and sister group affinities have not been studied with DNA methods. We used partial gene sequences for 28S rRNA, cytochrome oxidase I (cox1) and 16S rRNA (rrnL) for 158 species, representing most recognized subfamilies of Scarabaeidae, including 46 species of Hopliini. Combined analyses using maximum likelihood and Bayesian inference under the two preferred alignment parameters recovered the Hopliini as monophyletic. Hopliines were inserted at the base of a clade of Cetoniinae+Rutelinae+Dynastinae, being either recovered as their immediate sister group, or as part of an expanded set of basal branches that also includes the tribe Macrodactylini which has been classified as part of the Melolonthinae (may chafers). At the level of subtribes, we found Hopliina paraphyletic with respect to Pachycnemina which also includes the monophyletic clade of Heterochelina and Gymnolomina. Trait mapping under parsimony on the preferred tree resulted in inferences of three independent origins of sexual dimorphism, which coincided with shifts to ‘flower-embedding’ pollination. In contrast, night active taxa, which are general phyllophages as other pleurostict chafers, never show clear sexual dimorphism. South African lineages include several deep-branching lineages. The exceptional morphological and phylogenetic diversity of the South African fauna may therefore be due to their antiquity, in addition to sexual selection in the day-active lineages. Phylogenetic studies of the endemic South African plant radiations have demonstrated the repeated evolutionary shift to beetle pollination, but it remains to be investigated if this is driven by the hopliine pollinators present in the bioregion or by a propensity of the local plant lineages favoring this pollination syndrome.

Political Institutions, Policymaking Processes and Policy Outcomes in Chile

In this analysis we characterize the salient features of the Policy Making Process (PMP) in Chile. We emphasize the influence of political institutions on the PMP, and examine the linkage between policymaking and policy outcomes in Chile. To facilitate comparability with the other country-level studies in this collection of essays, we adopt the theoretical framework of Spiller and Tommasi which emphasizes the importance of transactions costs for the politics of policymaking. Because of the importance of veto players in the Chilean PMP we emphasize the importance of preference alignment (or the lack thereof) to explain variation across policy areas in the quality of policy outputs. Chile’s economic policies are generally stable to political shocks, flexible to new social and economic scenarios, mostly coherent, and promote economic growth, making it something of an outlier relative to other Latin American countries, though not in comparison with OECD countries. The quality of policies tends to be higher on macroeconomic areas, international integration, financial markets and regulations, than on more domestic issues—like labor markets, social security, health and education. On human rights and moral issues, policies show higher rigidity and overall lower quality. The salient features of the Chilean PMP are the electoral system, and the associated party system characterized by two long-lived coalitions; a powerful executive, with de facto control over the agenda; a relatively independent judiciary; and a bureaucracy that is relatively free from corruption even by the standards of the OECD, and a series of veto points in the policymaking process that permit adversely affected actors to block policy change. In the areas of human rights and military policy, the armed forces must be included among the set of veto players. . Consistently with the theoretical framework of Spiller and Tommasi, the small number of actors, who interact repeatedly, the predictability of policy implementation and of law enforcement, leads to a policy making process in which transaction costs are low and inter-temporal political exchanges are credible. The veto players help to give inter-temporal exchanges their credibility, but they can also block reforms. Looking at policy areas in cross section, we find that policy areas in which policymakers’ interests are more nearly aligned, and in which there is more rapid exogenous change, are associated with more successful efforts at reform, while areas in which the interests of the executive and the various veto players diverge, policy tends to stagnate.

Comment on Mosley (2010): Trust and conditionality, or can the World Bank Leopard change its spots

The core argument of the paper, that establishing trust between donors and recipients is central to successful aid conditionality, is plausible and convincing. While sympathetic to the lines of argument and analysis, I have reservations. First, there would be value in trying to distinguish between notions of trust and reputation. Although these may appear very similar, they are not identical; building a reputation for compliance can be seen as a means to establish trust and what we can observe (in an empirical context) are indicators of reputation. Second, while there is merit in the combination of case study and quantitative analysis to find evidence, I find the case studies more convincing; the econometric analysis is very unlikely to be robust. Another, perhaps minor, observation is that if there is trust, why then should there also be conditionality? White and Morrissey (1997) argue that in cases where donor and recipient preferences over reform are actually aligned conditionality is of no benefit, and indeed can generate the wrong signal if reformist recipients are asked to do too much. One could suggest that in circumstances of preference alignment, which would be expected to reflect trust, conditionality of the standard form (more strictly, tight conditionality) may be damaging, hence undermines the trust. The paper appears to appreciate this in reflecting on new forms of conditionality based more closely on ownership than ‘demands’ for policy reform, although the argument is not developed in terms of conditionality under trust. Rev Int Organ (2011) 6:453–456 DOI 10.1007/s11558-011-9117-6

A simulation study of microstructure evolution inside the shear band in biaxial compression test

AbstractWe study the development of microstructure inside the shear band in granular media consisting of elliptical‐shaped particles. Plane strain biaxial compression test was simulated using two‐dimensional distinct element method. The generation of large voids and concentration of excessive particle rotation inside a shear band are found in a quite similar manner to those observed in natural soils. Evolution of the microstructure inside and outside the shear band is studied. The magnitude and direction of particle rotation inside the shear band is influenced by orientation of long axes of elliptical particles. Because of such particle rotations inside the shear band, the preferred alignment of particles becomes horizontal in the residual state, which results in a more anisotropic contact normal distribution oriented along the major principal stress axis. Copyright © 2010 John Wiley & Sons, Ltd.

Winding sense of galaxies around the local supercluster

We present an analysis of the winding sense (S and Z-shapes) of 1621 field galaxies that have radial velocity between 3000 km s−1 and 5000 km s−1. The preferred alignments of S- and Z-shaped galaxies are studied using chi-square, autocorrelation and Fourier series tests. We classify all the galaxies into 32 subsamples and notice a good agreement between the position angle (PA) distribution of the S- and Z-shaped galaxies. The homogeneous distribution of the S- and Z-shaped galaxies is more noticeable for the late-type spirals (Sc, Scd, Sd and Sm) than for the early-types (Sa, Sab, Sb and Sbc). A significant dominance of S-mode galaxies is apparent in the barred spirals. A random alignment is evident in the PA-distribution of Z- and S-mode spirals. In addition, a homogeneous distribution of the S- and Z-shaped galaxies is found to be invariant under global expansion. The PA-distribution of the total S-mode galaxies is found to be random, whereas a preferred alignment is clear for all the Z-mode galaxies. It is found that the galactic planes of Z-mode galaxies tend to lie in the equatorial plane.

Methyl and Pentyl Chloride in a Microhydrated Environment and at the Liquid Water−Vapor Interface: A Theoretical Study

The solvation properties of methyl and pentyl chloride were studied in a microhydrated environment with up to 10 explicit water molecules and at the liquid water-vapor interface. Geometry optimizations were performed in the former case using the density functional based tight binding (DFTB), DFTB-D, and Møller-Plesset perturbation theory (MP2) levels of theory. The microhydrated alkyl chloride complexes were characterized in terms of hydrogen bonding and energetic stability. The DFTB and DFTB-D results were verified by comparison with those obtained by MP2. Good agreement between the MP2 and DFTB-D results is found. Complexes where the alkyl chloride molecule is attached to an edge of the water cluster are found to be most stable. Pronounced stability is also observed for cubic arrangements of the alkyl chloride-water complexes. Molecular dynamics simulations based on the DFTB and DFTB-D methods were used to study the adsorption process of the alkyl chloride molecules to a water surface. The dynamics simulations show that the methyl chloride molecule is located at the water surface preferentially with the methyl group oriented toward the water surface, while for pentyl chloride, owing to the longer nonpolar hydrocarbon chain, a parallel alignment at the water surface is found with the hydrocarbon chain pointing slightly to the gas phase. Despite some quantitative differences, the present work provides confirmation of the somewhat surprising preferential orientation of the methyl chloride molecule at the water-vapor interface predicted in a recent study using molecular dynamics simulations based on an empirical force field (Harper et al., J. Phys. Chem. A 2009, 113, 2015-2024). The observed difference in preferred alignment at the aqueous surface between the methyl chloride and the longer-chain alkyl chloride is likely to have consequences for the chemistry of alkyl halides adsorbed on the surface of aqueous and ice particles in the atmosphere.

PENUMBRAL FINE STRUCTURE AND DRIVING MECHANISMS OF LARGE-SCALE FLOWS IN SIMULATED SUNSPOTS

We analyze in detail the penumbral structure found in a recent radiative MHD simulation. Near tau=1, the simulation produces penumbral fine structure consistent with the observationally inferred interlocking comb structure. Fast outflows exceeding 8 km/s are present along almost horizontal stretches of the magnetic field; in the outer half of the penumbra, we see opposite polarity flux indicating flux returning beneath the surface. The bulk of the penumbral brightness is maintained by small-scale motions turning over on scales shorter than the length of a typical penumbral filament. The resulting vertical rms velocity at tau=1 is about half of that found in the quiet Sun. Radial outflows in the sunspot penumbra have two components. In the uppermost few 100 km, fast outflows are driven primarily through the horizontal component of the Lorentz force, which is confined to narrow boundary layers beneath tau=1, while the contribution from horizontal pressure gradients is reduced in comparison to granulation as a consequence of anisotropy. The resulting Evershed flow reaches its peak velocity near tau=1 and falls off rapidly with height. Outflows present in deeper layers result primarily from a preferred ring-like alignment of convection cells surrounding the sunspot. These flows reach amplitudes of about 50% of the convective rms velocity rather independent of depth. A preference for the outflow results from a combination of Lorentz force and pressure driving. While the Evershed flow dominates by velocity amplitude, most of the mass flux is present in deeper layers and likely related to a large-scale moat flow.

Opinions of a selected population of Nigerian dental surgeons on the preferred management of unerupted maxillary canines

Objective: To assess the survey opinions of Dental Surgeons working in one of the Nigerian Teaching Hospitals on their preferred management of unerupted maxillary canines.
 Method: The setting was the Dental Centre, University College Hospital, Ibadan. The participants were 46 Dental Surgeons working within the selected Teaching Hospital. The instrument of study was a questionnaire which consisted of 10 open ended questions, for information on questionnaire, sociodemographic characteristics. Data obtained from the questionnaire were analyzed and frequencies were generated.
 Result: Four main types of treatment were preferred by participants: 23(54.7%) of the dental surgeons preferred alignment with orthodontic treatment to all other forms of management, 12(28.6%) preferred surgical extraction, 5 (11%) preferred transplantation and 2 (4%) preferred observation and monitoring .
 Conclusion: Opinions of dental surgeons surveyed indicated that most dental surgeons would prefer orthodontic alignment of the unerupted maxillary canine above other dental treatment.