A Measurement System for On-line Estimation of Weed Coverage

This paper describes two different solutions for the estimation of weed coverage. Both measuring systems discriminate the weed from the ground by means of the color difference between the weed and ground and can be used to on-line control tractor sprayers in order to reduce weedkiller use. The solutions differ with respect to the sensor type: one solution is based on a digital camera and a computer that analyzes the images and determines the weed amount, while the other simpler solution makes use of two photo detectors and an analog processing system. The camera-based solution provides an uncertainty of a few percentage, while the photo detector-based one, though extremely cheap, has an uncertainty of about 5% and suffers from changes in light conditions, which can alter the estimation

On rational maps from a general surface in P^3 to surfaces of general type

We study the dominant rational maps from a general surface in P^{3} to surfaces of general type. We prove restrictions on the target surfaces, and special properties of the rational maps. We show that for a small degree the general surface has no such map. Moreover a slight improvement of a result of Catanese, on the number of moduli of a surface of general type, is also obtained.Comment: 19 pages, accepted in Advances in Geometr

Genome-wide scanning versus candidate gene approach in the genetic architecture of common diseases.

In the Nature 7 June issue, researchers from the Welcome Trust Case Control Consortium (WTCCC) reported the findings of a large genome-wide association (GWA) study of 14,000 cases of common diseases and 3000 controls studies revealing the role of several loci in the genetic risk of common diseases. 

We wish to emphasize that by making public the access to databases, consortia allow other investigators to search for association between candidate genes and T2D-related phenotypes. As an example we found, in a pilot study enrolling 1100 individuals that SNPs in the CLOCK (i.e. rs1554483 and rs6843722) were associated with hypertension (p value < 0.01, and 0.01, respectively). Interestingly, the same association was found by the WTCCC study (rs1554483, rs4580704, rs6843722 and rs4864548 with p<0.039, 0.014, 0.049 and 0.019). However, these findings were not mentioned by the authors because of the stringent p value criteria logically used by them in the face of a WGA

A note on spaces of symmetric matrices

We calculate the maximal dimension of linear spaces of symmetric and hermitian matrices with given high rank, generalizing a well-known result of Adams {\em et al.}Comment: 7 page

Algebraic functions with even monodromy

Let $X$ be a compact Riemann surface of genus $g$ and $d\geq 12g+4$ be an integer. We show that $X$ admits meromorphic functions with monodromy group equal to the alternating group $A_d.

Alternating groups and rational functions on surfaces

Let X be a smooth complex projective surface. We prove that for any sufficiently big m there exists a rational dominant map f from X into a complex rational ruled surface Y, such that f is generically finite of degree m and has monodromy the alternating group Am.Comment: 17 page