Combinatorics of BB-orbits and Bruhat--Chevalley order on involutions

Let $B$ be the group of invertible upper-triangular complex $n\times n$ matrices, $\mathfrak{u}$ the space of upper-triangular complex matrices with zeroes on the diagonal and $\mathfrak{u}^*$ its dual space. The group $B$ acts on $\mathfrak{u}^*$ by $(g.f)(x)=f(gxg^{-1})$, $g\in B$, $f\in\mathfrak{u}^*$, $x\in\mathfrak{u}$. To each involution $\sigma$ in $S_n$, the symmetric group on $n$ letters, one can assign the $B$-orbit $\Omega_{\sigma}\in\mathfrak{u}^*$. We present a combinatorial description of the partial order on the set of involutions induced by the orbit closures. The answer is given in terms of rook placements and is dual to A. Melnikov's results on $B$-orbits on $\mathfrak{u}$. Using results of F. Incitti, we also prove that this partial order coincides with the restriction of the Bruhat--Chevalley order to the set of involutions.Comment: 27 page

Investment, the Cost of Capital, and Monetary Policy in the Nineties in France: A Panel Data Investigation

Using a large panel of 6,946 French manufacturing firms, this paper investigates the effect of monetary policy on investment from 1990 to 1999 through the cost-of-capital and the cash-flow channels. We compare several specifications of neo-classical demand for capital, taking into account transitory dynamics. The user cost of capital has a significant negative elasticity with respect to capital using traditional Within estimates, or as long as cash-flow is not added to the regression when using Generalised Method of Moments estimates. Asymmetries of effect of monetary policy are evaluated for different groups of firms which differ in terms of informational asymmetries.When dummy variables related to firms which are more sensitive to cash-flow are added in the model, the user cost elasticity is significant again.

Mineral load on the paddock of organic sows in the Netherlands

The main aim of this study was to quantify nutrient deposition on the paddock in Dutch organic pig farms. Observations of excreting behaviour of grazing sows were carried out at three farms in each of two measuring seasons (spring/summer and autumn). The nutrient loads of N, P and K were calculated according to their content in urine and faeces, average weight of urine and faeces per excretion, and number of urinations and defecations done in the paddock. The N and P loads on the paddock varied greatly between the organic pig farms (P<0.01 for N, not significant for P and P<0.05 for K). The total amount of nutrients on two of the farms far exceeded the permitted levels (170 kg.ha-1year-1 for N and 44 kg.ha-1year-1 for P). On all three farms, faeces were unevenly distributed in the paddock. Regular rotation of paddocks resulted in a more uniform distribution

ST-segment elevation in the electrocardiogram: a sign of myocardial ischemia

In 1972 Kjekshus et al. published the seminal article ‘Distribution of myocardial injury and its relations to epicardial ST-segment changes after coronary occlusion in the dog' in Cardiovascular Research. In this article it was shown that the ST-segment elevation occurring early after occlusion of the left descending coronary artery was closely related to the depletion of the necrotic cells from creatine kinase and to flow reduction at a later stage (24 h). This correlation was especially prominent if the infarction was transmural. Starting from these phenomenological relationships, this article briefly describes and summarizes the experimental research which was carried out in other laboratories after the publication of Kjekshus et al. Special emphasis is laid on the discussion of the main basic mechanisms which underly the clinically observed ST-segment elevation and its evolution after the acute stage of ischemia, i.e. the changes in the transmembrane action potential and the alteration in electrical cell-to-cell couplin

En praktisk anvendelse av moderne porteføljeteori : den optimale porteføljen

Denne utredningen anvender moderne porteføljeteori med det formål å konstruere optimale porteføljer som gir risikojustert meravkastning på Oslo Børs (OSEBX). Den optimale porteføljen er sammensatt av passiv indeksforvaltning og aktive porteføljer. Konstrueringen av den optimale blandingen mellom passiv- og aktiv portefølje bygger på rammeverket til Treynor og Black som ble introdusert i 1973. Denne metoden og resultatene den gir er kritisk avhengig av inndata. Det er derfor en subjektiv vurdering underveis av hva som anses som god informasjon inn i optimeringsmodellen. For å vurdere nærmere prestasjonen til optimeringsmodellen, blir den optimale porteføljen sammenlignet med en enkel likevektet strategi. Dette for å vurdere om en eventuell risikojustert meravkastning i den optimale porteføljen kunne vært enda større ved å benytte en enkel strategi som ikke krever noen beregninger. Utredningen starter med å klargjøre forskjellene mellom passiv og aktiv forvaltning, og empiriske erfaringer vedrørende aktive strategier. Det er indikasjoner på at det finnes gode forvaltere som evner å skape risikojustert meravkastning. De samme studiene, som er gjort på fondsnivå, viser imidlertid at meravkastningene oftest forsvinner når det tas høyde for forvaltningskostnader. Det blir også vist at de få som evner å skape meravkastning sjelden klarer dette over tid. Videre er det en presentasjon av moderne porteføljeteori som bygger på Markowitz (1952) sitt rammeverk. I dette inngår faktormodeller som forklarer avkastning og risiko i aksjer eller porteføljer, samt porteføljekonstruksjon som kombinerer porteføljer på en optimal måte. Den empiriske undersøkelsen tar del i det norske aksjemarkedet. Utredningen har benyttet ukeporteføljene til DnB NOR Markets som inndata til den aktive delen, mens indeksen OSEBX er benyttet som passiv portefølje. Resultatene viser at den optimale porteføljen har oppnådd en meravkastning på 7,4 prosent etter kostnader i de 114 ukene som er optimert. Den risikojusterte meravkastningen målt ved informasjonsrate er på 0,82. Resultatene er meget gode ut ifra tidligere empiriske studier av informasjonsrater, men de er i midlertidig ikke statistisk signifikant med et signifikansnivå på 5 prosent. Mer interessant er en sammenligning mellom den teoretiske modellen og en enkel likevektet modell. Det viser seg at en enkel likevektet modell, med samme vekter i aktiv og passiv portefølje som den optimale porteføljen, oppnådde et bedre resultat. Den teoretiske optimeringsmodellen har derfor kommet til kort for en enkel likevektet strategi

Challenges and proposed solutions towards telecentre sustainability : a southern Africa case study

Access to information through telecentres is essential for social and economical growth in rural areas of sub-Saharan Africa. While many governments have established telecentres as means of bridging the increasingly wide digital divide in rural or unserved areas, their corresponding sustainability or continual operation is in doubt due to various challenges. These challenges to information and communications technology (ICT) access has resulted in many of the rural population being unable to exploit the potential of promoting social economic development through innovative business solutions and education. In this study we evaluate the sustainability of telecentres in Zambia and South Africa and propose possible solutions to the problems that telecentres face. Strictly speaking, we focus on two telecentres; Comsol telecentre in KZN, South Africa and Kanyonyo Resource Centre in Mongu, Zambia

Extra snijmais goed voor welzijn varkens

Vleesvarkens hebben graag een emmer snijmais. Dat blijkt uit praktijkonderzoek op Varkens Innovatie Centrum Sterksel, onderdeel van Wageningen UR. In vergelijking met stro heeft snijmais meer voederwaarde en het leidt minder snel tot verstoppingen in de mestput

Process alternatives for bioethanol production from organosolv pretreatment using lignocellulosic biomass

Organosolv pretreatment makes use of ethanol as a solvent to remove lignin and render the cellulose and hemicellulose present in the biomass available for conversion. However, solvent recovery is a crucial step to make organosolv pretreatment a competitive and reliable alternative for second generation bioethanol production. We used Aspen Plus v8.0 to simulate an initial organosolv pretreatment case based on published experimental works and proposed 4 different alternatives for the solvent ethanol recovery. Total energy consumption, ethanol productivity, ethanol concentration after fermentation, capital costs, variable costs and minimum ethanol selling price (MESP) were evaluated for the selection of the best design for the process. Furthermore, energy targets were calculated for the scenarios to investigate the saving potentials in the variable costs and were accounted for new MESP calculations. Ethanol productivity and recovery was similar for all the cases evaluated. The capital cost calculated for the base case was 20.8 million dollars and the total energy consumption was 732 MW, with a MESP of 1.117 $/kg of ethanol. The best process alternative with energy integration obtained savings of almost 30$/kg of ethanol and the total energy consumption was 488 MW.</p