Geometric aspects of the symmetric inverse M-matrix problem

We investigate the symmetric inverse M-matrix problem from a geometric perspective. The central question in this geometric context is, which conditions on the k-dimensional facets of an n-simplex S guarantee that S has no obtuse dihedral angles. First we study the properties of an n-simplex S whose k-facets are all nonobtuse, and generalize some classical results by Fiedler. We prove that if all (n-1)-facets of an n-simplex S are nonobtuse, each makes at most one obtuse dihedral angle with another facet. This helps to identify a special type of tetrahedron, which we will call sub-orthocentric, with the property that if all tetrahedral facets of S are sub-orthocentric, then S is nonobtuse. Rephrased in the language of linear algebra, this constitutes a purely geometric proof of the fact that each symmetric ultrametric matrix is the inverse of a weakly diagonally dominant M-matrix. Review papers support our belief that the linear algebraic perspective on the inverse M-matrix problem dominates the literature. The geometric perspective however connects sign properties of entries of inverses of a symmetric positive definite matrix to the dihedral angle properties of an underlying simplex, and enables an explicit visualization of how these angles and signs can be manipulated. This will serve to formulate purely geometric conditions on the k-facets of an n-simplex S that may render S nonobtuse also for k>3. For this, we generalize the class of sub-orthocentric tetrahedra that gives rise to the class of ultrametric matrices, to sub-orthocentric simplices that define symmetric positive definite matrices A with special types of k x k principal submatrices for k>3. Each sub-orthocentric simplices is nonobtuse, and we conjecture that any simplex with sub-orthocentric facets only, is sub-orthocentric itself.Comment: 42 pages, 20 figure

Assessment of broiler chicken welfare in Southern Brazil

Scientific literature on broiler chicken welfare in Brazilian industrial systems is scarce. This study aimed at assessing broiler chicken welfare on industrial farms in the State of Rio Grande do Sul, Southern Brazil, using the Welfare Quality (R) assessment protocol for poultry, to provide directly applicable scientific information. Results are presented as criteria scores ranging from 0 to 100, with higher scores indicating better welfare; and percentages of prevalence. The scores classified as excellent (above 80) were absence of prolonged thirst, absence of prolonged hunger, litter quality, breast blister and touch test. Enhanced scores (between 55 and 80) were comfort around resting, plumage cleanliness and dust sheet test. Acceptable scores (between 20 and 55) were thermal comfort, stocking density, absence of injuries, footpad dermatitis and hock burn; and unacceptable scores (below 20) were lameness and qualitative behavioral assessment. The median percentage of mortality and culled birds were 5.2% and 0.6%, respectively. This study provides useful information to select priorities of action on assessed farms and may contribute for setting up legal standards and guiding decisions related to animal welfare issues in Brazil

Milloin kansanrunoutemme kehitys saavutti huippunsa?

Suomessa kehitettiin 1800-luvun lopulla ensimmäinen tieteellisenä pidetty menetelmä kansanrunouden tutkimiseen. Menetelmä tunnetaan maantieteellis- historiallisena metodina ja siihen nojaava tutkimussuuntaus suomalaisena koulukuntana. Tämän perustan laski Julius Krohn (1835–88). Hänen poikansa Kaarle Krohn (1863–1933) teki kansainvälisen läpimurtonsa kansansatujen tutkijana mutta jatkoi sitten isänsä aloittamaa työtä kalevalaisen runouden ja suomalaisen mytologian saralla. Uuden koulukunnan kunnianhimoisena tavoitteena oli selvittää eurooppalaisten perinteenlajien synty ja kehityshistoria

Satugenre kirjallisuudentutkimuksen ja folkloristiikan riitamaana

Esitelmä Suomen Kansantietouden Tutkijain Seuran VI Kevätkoulun Eminentia-luennot-seminaarissa 15.5.2012 Tieteiden talossa Helsingissä

Viina, valta ja agraarinen perhe

Summary: Alcohol, power and the pre-industrial community