The cause of axial rotation of the scoliotic spine

To explain the cause of axial rotation in a scoliotic vertebral column, the influence of the gravitation force on a spine with a C-scoliosis has been investigated by means of a mechanical model. In this model the gravitation force takes hold of the three-dimensionally curved vertebral column eccentrically. From these reflections it appears that the axial rotation in the scoliotic spine can be explained by the moment distribution caused by this eccentrical gravitation force. The moment distribution, necessary for correction of the spine, is supposed to be opposite to the moments caused by the gravitation force. The moment distribution caused by the Harrington and the Luque spinal correction systems are compared to the calculated optimum correction moments. It appears that the moment distribution for the Harrington and Luque methods, necessary for the correction of the lateral deviation, are almost the same as the calculated correction moments. But the axial rotation appears to be increasing instead of decreasing in both correction systems

Biogrondstoffen; van fossiel naar biomassa

Er is een oneindige voorraad planten dankzij de straling van de zon. Er zijn op aarde voldoende grond en biologische afvalstromen beschikbaar om een groot deel van de wereldbehoefte aan energie te vervullen en zo te komen tot een biobased economy. Het cahier Biogrondstoffen beschrijft de mogelijkheden en technieken om biomassa te verkrijgen en om te zetten in bruikbare en commercieel toepasbare biogrondstoffen. Het cahier besteedt ook aandacht aan de belemmeringen voor een dergelijke groene economie. Een duurzame productie van biomassa en biobrandstoffen op grote schaal vereist goede voorwaarden, zodat de omstandigheden van mensen in arme landen en het milieu niet verslechteren, maar juist verbeteren. Met die gedachte en gezien de ontwikkelingen in de technologie, is de redactie van het cahier voorzichtig optimistisch over de toekomst van een groene, mede op biomassa georiënteerde, economie

Valorisation of lignin – Achievements of the LignoValue project

Lignocellulosic biorefinery for production of biofuels, materials and chemicals requires valorization of all fractions including lignin. As a consequence of its poly-aromatic structure, lignin potentially serves as a source for aromatic chemicals. The developed biorefinery concept of the LignoValue project comprises two major steps: (1) Organosolv fractionation of wheat straw and willow into (hemi)cellulose and high purity lignin. (2) Further conversion of the isolated lignin via catalytic pyrolysis, supercritical depolymerization and partial hydrodeoxygenation (HDO) into different components like low molecular phenolic compounds, wood adhesives and fuel additives. The cellulose fraction resulting after organosolv fractionation is effectively hydrolysed by enzymes for biofuel production. Quality assessment of the liberated lignins shows interesting characteristics for follow-up chemistry such as high purity, relatively low molar mass and polydispersity. Catalytic pyrolysis in a fluidised bed at 400-500°C was found to convert organosolv lignin in 35-55% phenolic oil, 10% identified monomeric phenolic compounds, 10-20% water, 5-20% gas and 35-55% char. Supercritical depolymerisation of lignin in carbon dioxide based solvents resulted in a similar spectrum of products, however, at a lower temperature (ca 300°C) but at higher pressures. In both thermochemical processes the use of promotors or catalysts lead to an improved yield of the target monomeric aromatic products. Also the residual char fraction shows interesting properties for use in bio-char applications. Catalytic semi-continuous HDO of lignin in hydrogen atmosphere can be manipulated to yield both light oils or heavy oils as potential additives to fuels. Suitable catalysts were found to convert depolymerised lignin to phenolic oils in high yields. In this process no char formation is observed. The lignin oils were successfully tested on lab scale as partial substitution of phenol in resins for gluing wood panels. The LignoValue concept is critically reviewed in a techno-economic analysis demonstrating the potential for further commercial development and adoptation of this innovative biorefinery process in Europe

Modderige bermen? Hoe gemeenten omgaan met verkeerseffecten van nieuwe functies in het buitengebied - een verkenning

In de lange geschiedenis van het Nederlandse platteland is nu een stadium aangebroken van zogenaamd verbreed gebruik. Dit speelt deels in de landbouw zelf (zorgboerderij, kamperen bij de boer). Daarnaast wordt het buitengebied in toenemende mate gebruikt door nieuwe functies, zoals tuincentra, opslag, e.d. Voor deze plattelandsverbreding treedt doorgaans de afdeling Ruimtelijke Ordening van de gemeente op als vergunningverlener. Deze plattelandsverbreding heeft echter ook effecten op omvang en samenstelling van het verkeer op de plattelandswegen. De vraag is hoe de gemeentelijke afdeling Verkeer, in de hoedanigheid van wegbeheerder, hiermee omgaat en of sprake is van afstemming tussen beide beleidsterreinen. Aan de hand van enkele voorbeelden is hiervan een eerste beeld verkrege

Coherent Phonon Dynamics in Short-Period InAs/GaSb Superlattices

We have performed ultrafast pump-probe spectroscopy studies on a series of InAs/GaSb-based short-period superlattice (SL) samples with periods ranging from 46 \AA to 71 \AA. We observe two types of oscillations in the differential reflectivity with fast ($\sim$ 1- 2 ps) and slow ($\sim$ 24 ps) periods. The period of the fast oscillations changes with the SL period and can be explained as coherent acoustic phonons generated from carriers photoexcited within the SL. This mode provides an accurate method for determining the SL period and assessing interface quality. The period of the slow mode depends on the wavelength of the probe pulse and can be understood as a propagating coherent phonon wavepacket modulating the reflectivity of the probe pulse as it travels from the surface into the sample.Comment: 6 pages, 4 figure

Radiating dipoles in photonic crystals

The radiation dynamics of a dipole antenna embedded in a Photonic Crystal are modeled by an initially excited harmonic oscillator coupled to a non--Markovian bath of harmonic oscillators representing the colored electromagnetic vacuum within the crystal. Realistic coupling constants based on the natural modes of the Photonic Crystal, i.e., Bloch waves and their associated dispersion relation, are derived. For simple model systems, well-known results such as decay times and emission spectra are reproduced. This approach enables direct incorporation of realistic band structure computations into studies of radiative emission from atoms and molecules within photonic crystals. We therefore provide a predictive and interpretative tool for experiments in both the microwave and optical regimes.Comment: Phys. Rev. E, accepte