Scaling Ratios and Triangles in Siegel Disks

Let $f(z)=e^{2i\pi\theta} z+z^2$, where $\theta$ is a quadratic irrational. McMullen proved that the Siegel disk for $f$ is self-similar about the critical point. We give a lower bound for the ratio of self-similarity, and we show that if $\theta=(\sqrt 5-1)/2$ is the golden mean, then there exists a triangle contained in the Siegel disk, and with one vertex at the critical point. This answers a 15 year old conjecture.Comment: 13 pages, 13 PostScript figure

The Medusa Algorithm for Polynomial Matings

The Medusa algorithm takes as input two postcritically finite quadratic polynomials and outputs the quadratic rational map which is the mating of the two polynomials (if it exists). Specifically, the output is a sequence of approximations for the parameters of the rational map, as well as an image of its Julia set. Whether these approximations converge is answered using Thurston's topological characterization of rational maps. This algorithm was designed by John Hamal Hubbard, and implemented in 1998 by Christian Henriksen and REU students David Farris, and Kuon Ju Liu. In this paper we describe the algorithm and its implementation, discuss some output from the program (including many pictures) and related questions. Specifically, we include images and a discussion for some shared matings, Lattes examples, and tuning sequences of matings.Comment: 25 pages, many figures, submitte

Inter-row subsoiling increases marketable yield in potatoes

Inter-row subsoiling increased average yield of 40-65 mm potatoes by 14 pct during 2001-2003. But there were significant differences between the years. In 2001, the yield increased by 49 pct, whereas it was unaffected or decreased in 2002 and 2003. Better understanding of optimal subsoiling conditions is needed to exploit the benefit of inter-row subsoiling

Less intra-row weeds – experiences with a punch planter and a cycloid hoe based on GPS

Experiences with a punch planter and an intelligent rotary tine weeder are summarized. The objectives were to investigate (1) to what extent punch planting and pre-emergence flame weeding can reduce intra-row weed emergence in direct sown crops like onion, carrot and sugar beet, (2) to what extent an intelligent intra-row weeder, a cycloid hoe based on RTK-GPS technology, can control intra-row weeds without damaging the crop in direct sown crops, (3) and to what extent there exists synergy between punch planting with pre-emergence flame weeding and mechanical intra-row weeding

Kamme - et alternativ til pløjning?

På Landbohøjskolen arbejder vi på at udvikle et jordbearbejdningssystem, der er tænkt som et alternativ til pløjning. Det er baseret på kamme. Systemet er inspireret af Kemink Exact Jordbehandlingssystemet, som kendetegnes ved kamme, faste kørespor og dybe jordløsninger

Erfaringer med kamme som alternativ til pløjning

Reduceret jordbehandling er ønskelig, men er det muligt ved økologisk drift? Et alternativ til pløjning kunne være opsætning af kamme i dyrkningen af rækkeafgrøder. Mulighederne undersøges på KVL

Dybe jordløsninger i kartofler

Dybe jordløsninger øgede udbyttet af salgbare knolde med 14% i et tre-årigt markforsøg, men der var store forskelle mellem årene. I 2001 var udbyttet af salgbare knolde 49% højere mens det totale udbytte blev øget med 5%. I 2002 var der ikke nogen effekt og i 2003 reducerede dybe jordløsninger det totale knoldudbytte med 7%. Uddybende forsøg vil være nødvendige for at undersøge om det er muligt at opnå vedvarende højere salgbare udbytter ved at time de dybe jordløsninger i forhold til vækststadie og nedbørsmængde

Positiv effekt af kamdyrkning

Det netop afsluttede FØJO-II projekt CARMINA har givet følgende hovedresultater: Pløjefri dyrkning kombineret med kamme opsat om vinteren kan reducere udvaskningen af kvælstof på lerjord og er et muligt alternativ til almindelig kartoffeldyrkning. Dybe jordløsninger i vækstsæsonen kan under gunstige omstændigheder øge udbyttet i kartofler. Endvidere har kamdyrkning efter pløjning vist potentiale til at øge udbyttet i majs