A weak lensing comparability study of galaxy mergers that host AGNs

We compared the total mass density profiles of three different types of galaxies using weak gravitational lensing: (i) 29 galaxies that host quasars at z~0.32 that are in a post-starburst (PSQ) phase with high star formation indicating recent merger activity, (ii) 22 large elliptical galaxies from the SLACS sample that do not host a quasar at z~0.23, and (iii) 17 galaxies that host moderately luminous quasars at z~0.36 powered by disk instabilities, but with no intense star formation. On an initial test we found no evidence for a connection between the merger state of a galaxy and the profile of the halo, with the PSQ profile comparable to that of the other two samples and consistent with the Leauthaud et al. (2014) study of moderately luminous quasars in COSMOS. Given the compatibility of the two quasar samples, we combined these and found no evidence for any connection between black hole activity and the dark matter halo. All three mass profiles remained compatible with isothermality given the present data.Comment: 6 pages, 3 figures, 1 table, ACCEPTED MNRA

Do Brain Drain and Poverty Result from Coordination Failures?

We explore the complementarities between high-skill emigration and poverty in developing countries. We build a model endogenizing human-capital accumulation, high-skill migration and productivity. Two countries sharing the same characteristics may end up either in a "low poverty/low brain drain" path or in a "high poverty/high brain drain" path. After identifying country-specific parameters, we find that, for a majority of countries, the observed equilibrium has higher income than the other possible one. In 22 developing countries (including 20 small states with less than 2 million inhabitants), poverty and high brain drain are worsened by a coordination failure. For 25 other countries, a radical worsening of economic performances is feasible. These results are fairly robust to identification assumptions and the inclusion of a brain-gain mechanism.Public Good, Inequality Aversion, Immigration policy

An Incentive Mechanism to Break the Low-skill Immigration Deadlock

Although movements of capital, goods and services are growing in importance, workers movements are impeded by restrictive policies in rich countries. Such regulations carry substantial economic costs for developing countries, and prevent global inequality from declining. Even if rich countries are averse to global inequality, a single country lacks incentives to welcome additional migrants as it would bear the costs alone while the benefits accrue to all rich states. Aversion to global inequality confers a public good nature to the South-North migration of low-skill workers. We propose an alternative allocation of labor maximizing global welfare subject to the constraints that the rich countries are at least as well off as in the current "nationalist" (or "Nashionalist") situation. This "no regret" allocation can be decentralized by a tax-subsidy scheme which makes people internalize the fact that as soon as a rich country welcomes an additional migrant, global inequalities are reduced, and each citizen in the rich world is better off too. Our model is calibrated using statistics on immigration, working-age population and output. We simulate the proposed scheme on different sets of rich countries.Public Good, Inequality Aversion, Immigration policy

Do Brain Drain and Poverty Result from Coordination Failures?

We explore the complementarities between high-skill emigration and poverty in developing countries. We build a model endogenizing human-capital accumulation, high-skill migration and productivity. Two countries sharing the same characteristics may end up either in a “low poverty/low brain drain” path or in a “high poverty/high brain drain” path. After identifying country-specific parameters, we find that, for a majority of countries, the observed equilibrium has higher income than the other possible one. In 22 developing countries (including 20 small states with less than 2 million inhabitants), poverty and high brain drain are worsened by a coordination failure. For 25 other countries, a radical worsening of economic performances is feasible. These results are fairly robust to identification assumptions and the inclusion of a brain-gain mechanism.Brain drain, Development, Multiple equilibria, Coordination failure

Consistency Conditions for Brane Worlds in Arbitrary Dimensions

We consider ``brane world sum rules'' for compactifications involving an arbitrary number of spacetime dimensions. One of the most striking results derived from such consistency conditions is the necessity for negative tension branes to appear in five--dimensional scenarios. We show how this result is easily evaded for brane world models with more than five dimensions. As an example, we consider a novel realization of the Randall--Sundrum scenario in six dimensions involving only positive tension branes.Comment: 18 pages, LaTex, refs. adde

Spectral interferometric polarised coherent anti-Stokes Raman spectroscopy

We have developed an interferometric implementation of coherent anti-Stokes Raman scattering (CARS) which enables broadband coherent Raman spectroscopy free from non-resonant background (NRB), with a signal strength proportional to concentration. Spectra encode mode symmetry information into the amplitude response which can be directly compared to polarised spontaneous Raman spectra. The method requires only passive polarisation optics and is suitable for a wide range of laser linewidths and pulse durationsComment: 5 pages, 3 figures, submitted to PR

Two-channel Kondo physics in tunnel-coupled double quantum dots

We investigate theoretically the possibility of observing two-channel Kondo (2CK) physics in tunnel-coupled double quantum dots (TCDQDs), at both zero and finite magnetic fields; taking the two-impurity Anderson model (2AIM) as the basic TCDQD model, together with effective low-energy models arising from it by Schrieffer-Wolff transformations to second and third order in the tunnel couplings. The models are studied primarily using Wilson's numerical renormalization group. At zero-field our basic conclusion is that while 2CK physics arises in principle provided the system is sufficiently strongly-correlated, the temperature window over which it could be observed is much lower than is experimentally feasible. This finding disagrees with recent work on the problem, and we explain why. At finite field, we show that the quantum phase transition known to arise at zero-field in the two-impurity Kondo model (2IKM), with an essentially 2CK quantum critical point, persists at finite fields. This raises the prospect of access to 2CK physics by tuning a magnetic field, although preliminary investigation suggests this to be even less feasible than at zero field.Comment: 10 pages, 8 figures. Version as published in PR

Non-invasive quantification of lower limb mechanical alignment in flexion

Objective: Non-invasive navigation techniques have recently been developed to determine mechanical femorotibial alignment (MFTA) in extension. The primary aim of this study was to evaluate the precision and accuracy of an image-free navigation system with new software designed to provide multiple kinematic measurements of the knee. The secondary aim was to test two types of strap material used to attach optical trackers to the lower limb. Methods: Seventy-two registrations were carried out on 6 intact embalmed cadaveric specimens (mean age: 77.8 ± 12 years). A validated fabric strap, bone screws and novel rubber strap were used to secure the passive tracker baseplate for four full experiments with each knee. The MFTA angle was measured under the conditions of no applied stress, valgus stress, and varus stress. These measurements were carried out at full extension and at 30°, 40°, 50° and 60° of flexion. Intraclass correlation coefficients, repeatability coefficients, and limits of agreement (LOA) were used to convey precision and agreement in measuring MFTA with respect to each of the independent variables, i.e., degree of flexion, applied coronal stress, and method of tracker fixation. Based on the current literature, a repeatability coefficient and LOA of ≤3° were deemed acceptable. Results: The mean fixed flexion for the 6 specimens was 12.8° (range: 6–20°). The mean repeatability coefficient measuring MFTA in extension with screws or fabric strapping of the baseplate was ≤2°, compared to 2.3° using rubber strapping. When flexing the knee, MFTA measurements taken using screws or fabric straps remained precise (repeatability coefficient ≤3°) throughout the tested range of flexion (12.8–60°); however, using rubber straps, the repeatability coefficient was >3° beyond 50° flexion. In general, applying a varus/valgus stress while measuring MFTA decreased precision beyond 40° flexion. Using fabric strapping, excellent repeatability (coefficient ≤2°) was observed until 40° flexion; however, beyond 50° flexion, the repeatability coefficient was >3°. As was the case with precision, agreement between the invasive and non-invasive systems was satisfactory in extension and worsened with flexion. Mean limits of agreement between the invasive and non-invasive system using fabric strapping to assess MFTA were 3° (range: 2.3–3.8°) with no stress applied and 3.9° (range: 2.8–5.2°) with varus and valgus stress. Using rubber strapping, the corresponding values were 4.4° (range: 2.8–8.5°) with no stress applied, 5.5° (range: 3.3–9.0°) with varus stress, and 5.6° (range: 3.3–11.9°) with valgus stress. Discussion: Acceptable precision and accuracy may be possible when measuring knee kinematics in early flexion using a non-invasive system; however, we do not believe passive trackers should be mounted with rubber strapping such as was used in this study. Flexing the knee appears to decrease the precision and accuracy of the system. The functions of this new software using image-free navigation technology have many potential clinical applications, including assessment of bony and soft tissue deformity, pre-operative planning, and post-operative evaluation, as well as in further pure research comparing kinematics of the normal and pathological knee