Essential dimension and pro-finite group schemes

A. Vistoli observed that, if Grothendieck's section conjecture is true and $X$ is a smooth hyperbolic curve over a field finitely generated over $\mathbb{Q}$, then $\underline{\pi}_{1}(X)$ should somehow have essential dimension $1$. We prove that an infinite, pro-finite \'etale group scheme always has infinite essential dimension. We introduce a variant of essential dimension, the fce dimension $\operatorname{fced} G$ of a pro-finite group scheme $G$, which naturally coincides with $\operatorname{ed} G$ if $G$ is finite but has a better behaviour in the pro-finite case. Grothendieck's section conjecture implies $\operatorname{fced}\underline{\pi}_{1}(X)=\dim X=1$ for $X$ as above. We prove that, if $A$ is an abelian variety over a field finitely generated over $\mathbb{Q}$, then $\operatorname{fced}\underline{\pi}_{1}(A)=\operatorname{fced} TA=\dim A$.Comment: Simplified proofs and stronger results in the new versio

MEXICO'S EJIDO REFORMS: THEIR IMPACT ON THE FUNCTIONING OF FACTOR MARKETS AND LAND ACCESS

The constitutional reforms undertaken in Mexico in 1992, as well as the systematic implementation of a program of land rights regularization (Procede), aimed to improve the security and transferability of property rights in order to create the pre-conditions for better functioning of factor markets in rural areas. The paper examines the extent to which this has materialized by exploring systematic differences over time between certified and non-certified ejidos as well as the private sector. We find that land rental markets function better in ejidos that underwent Procede, where there was also a marked increase in households' use of common pasture land. At the same time, neither the reforms nor Procede appear to have had much impact on land sales markets and ejidatarios' credit access. Implications for policy and program design are discussed.Land Economics/Use,

Polarimetric Control of Reflective Metasurfaces

This letter addresses the synthesis of reflective cells approaching a given desired Floquet's scattering matrix. This work is motivated by the need to obtain much finer control of reflective metasurfaces by controlling not only their co-polarized reflection but also their cross-coupling behavior. The demonstrated capability will enable more powerful design approaches -involving all field components in phase and magnitude- and consequently better performance in applications involving reflective metasurfaces. We first expose some fundamental theoretical constraints on the cell scattering parameters. Then, a successful procedure for controlling all four scattering parameters by applying parallelogram and trapezoid transformations to square patches is presented, considering both normal and oblique incidence

New genus, three new species and new records of Herpyllobiidae Hansen, 1892 (Crustacea, Copepoda) parasites of polychaetes from Antarctica

During the Antarctic Polarstern cruises ANT XIX/3 (ANDEEP-I), XIX/5 (LAMPOS), and XXI/2 (BENDEX) new material of symbiotic copepods associated with polynoid polychaetes was collected. Here the authors present results for the highly modified family Herpyllobiidae Hansen, 1892. New records of Herpyllobius antarcticus Vanhöffen, 1913 and Herpyllobius polarsterni López-González, Bresciani and Conradi, 2000 are provided from the eastern Weddell Sea and Bouvet Island respectively. A new species of the genus Eurysilenium Sars, 1870, E. australis, is described from specimens collected at the eastern Weddell Sea. A new genus, Gottoniella gen. nov., is proposed to include two species, G. antarctica sp. nov. and G. andeepi sp. nov., described from material collected from the Weddell Sea and Scotia Arc

In Search of a Strategy for Making Growth More Pro-Poor in the Philippines

The main driver of poverty reduction has shifted from agricultural to non-agricultural income growth in rural Philippines in the past two decades. Agricultural growth is still relatively more important (vis-à-vis non-agricultural growth), however, in reducing rural poverty in relatively more isolated provinces. Our results suggest that agricultural investments should focus on areas with underdeveloped infrastructure but with comparative advantage in agriculture. At the same time, non-agricultural income growth can be made more pro-poor by investing in mobility infrastructure and health, facilitating international labor migration, and lowering income inequality.poverty, growth and inequality, pro-poor growth, role of agriculture, the Philippines, Asia

Static Analysis of Circuits for Security

The purpose of the present work is to define a methodology to analyze a system description given in VHDL code and test its security properties. In particular the analysis is aimed at ensuring that a malicious user cannot make a circuit output the secret data it contains

The field of moduli of plane curves

It is a classical fact going back to F. Klein that an elliptic curve $E$ over $\bar{\mathbb{Q}}$ is defined by a homogeneous polynomial in $3$ variables with coefficients in $\mathbb{Q}(j_{E})$, where $j_{E}$ is the $j$-invariant of $E$, and $\mathbb{Q}(j_{E})$ is the field of moduli of $E$. The general definition of field of moduli goes back to T. Matsusaka and G. Shimura. With few exceptions, it coincides with the intersection of the fields where the curve is defined. We prove that every smooth plane curve of degree prime with $6$ is defined by a homogeneous polynomial with coefficients in the field of moduli. Furthermore, we show that most plane curves in arbitrary degree, and more generally most algebraic cycles in $\mathbb{P}^{2}$ with finite automorphism group, descend to a Brauer-Severi surface over the field of moduli

Modelling, Identification and Control of a Quadrotor Helicopter

This thesis work focused on the study of a quadrotor helicopter. The dynamic system modelling and the control algorithm evaluation were carried out. To test the results, a simulator and a real platform were developed. The Newton-Euler formalism was used to model the dynamic system. Particular attention was given to the group composed of the DC-motor, the gear box and the propeller which needed also the estimation of aerodynamic lift and torque to reach better accuracy. PID control algorithms were compared. The first stage tests were performed on a simulated model where it was easy to evaluate the performance with a mathematical approach. The second stage tests were carried out on the quadrotor platform to evaluate the behavior of the real system. A simulator based on Matlab-Simulink was developed. With this program it was possible to test the accuracy of the model and the robustness of the control algorithms. Furthermore a 3D graphic output and a joystick interface made easier the testability and the observability of the system. A quadrotor platform was developed. The electronics was composed of a Micro Control Unit (MCU) interfaced with several devices: the power supply, the receiving unit, the DC-motor power boards, the Inertial Measurement Unit (IMU), the SONAR and the IR modules. Thanks to these devices and the MCU software, both guided and autonomous flights were possible

Estudos clínicos utilizando o Tratamento Restaurador Atraumático (TRA) em dentes decíduos e permanentes

Este artigo apresenta uma revisão da literatura relacionada a estudos clínicos utilizando o tratamento restaurador atraumático (ART). A literatura científica disponível mostra-se encorajadoura em termos de controle da doença cárie através desta abordagem, especialmente em cavidades de uma superfície. Os passos clínicos da técnica são descritos e pontos de crucial importância enfatizados. A incorporação do tratamento restaurador atraumático em serviços de atenção básica à saúde , como o Programa de Saúde da Família, é considerada.This paper presents a review of the literature on clinical trials with Atraumatic Restorative Treatment. The available scientific literature is encouraging in terms of management of dental caries by this approach, especially for one-surface lesions. The steps of ART are described and the crucial points highlighted. The incorporation of ART into primary health care services, as Family Health Program - PSF, was considered

On the section conjecture over fields of finite type

Assume that the section conjecture holds over number fields. We prove then that it holds for a broad class of curves over finitely generated extensions of $\mathbb{Q}$. This class contains a non-empty open subset of any smooth curve, and all hyperbolic ramified coverings of curves of genus at least $1$ defined over number fields. Our method also gives an independent proof of the recent result by Sa\"idi and Tyler of the fact that the birational section conjecture over number fields implies it over finitely generated extensions of $\mathbb{Q}$