Ompløjning af afgræsningsmarker

I flerårige afgræsningsmarker sker en betydelig ophobning af kvælstof (N), som ved ompløjning kan frigives og resultere i en stor nitratudvaskning. Forsøg på en lerblandet sandjord viser, at når god landbrugspraksis følges (forårspløjning og brug af efterafgrøder) giver de flerårige græsmarker en betydelig forfrugtsværdi i to år efter ompløjning, uden at nitratkoncentrationen i udvaskningsvandet overstiger EU’s grænseværdi for drikkevand på 50 mg pr. liter

Matter-positronium interaction: An exact diagonalization study of the He atom - positronium system

The many-body system comprising a He nucleus, three electrons, and a positron has been studied using the exact diagonalization technique. The purpose has been to clarify to which extent the system can be considered as a distinguishable positronium (Ps) atom interacting with a He atom and, thereby, to pave the way to a practical atomistic modeling of Ps states and annihilation in matter. The maximum value of the distance between the positron and the nucleus is constrained and the Ps atom at different distances from the nucleus is identified from the electron and positron densities, as well as from the electron-positron distance and center-of-mass distributions. The polarization of the Ps atom increases as its distance from the nucleus decreases. A depletion of the He electron density, particularly large at low density values, has been observed. The ortho-Ps pick-off annihilation rate calculated as the overlap of the positron and the free He electron densities has to be corrected for the observed depletion, specially at large pores/voids.Comment: 18 pages, 8 figure

Forfrugtsværdi og N-udvaskning efter ompløjning af flerårige græsmarker med forskellige forhistorier

Undersøgelsens formål var at forbedre kvælstofudnyttelsen og mindske uønskede miljømæssige konsekvenser af sædskiftet på intensive malkekvægsbedrifter. Eftervirkningen af seks forskellige græsmarkstyper (1994-96) på udbytte og nitratudvaskning i de efterfølgende kornafgrøder (1997-99) blev undersøgt på lerblandet sandjord ved Forskningscenter Foulum. Græsmarkerne var ugødet kløvergræs og gødet rajgræs enten til slæt eller afgræsset med malkekøer fodret med to niveauer af N i suppleringsfoder. I det første år efter ompløjning var der tilstrækkeligt eftervirkning af afgræsningsmarkerne til at overflødiggøre yderligere gødningstilførsel, men i de følgende år var der gradvist behov for mere N-gødning for at opnå optimale udbytter. Jordbehandling blev undersøgt som en strategi til at synkronisere N-mineralisering med planternes behov efter ompløjning af græsmarkerne. Der blev sammenlignet fræsning forud for pløjning med pløjning alene. Fræsning forøgede jordens nitratindhold som tegn på en meget hurtig netto-mineralisering på trods af lave jordtemperaturer (5-10°C). Fræsning af grønsværen forud for ompløjning havde en positiv effekt på både udbytte og N-optagelse i den efterfølgende afgrøde. Andet år efter ompløjning, hvor der stadig var forfrugtsværdi fra græsmarkerne, var der stadig en positiv effekt af at fræse rajgræs-efterafgrøden før pløjning. Nitratudvaskningen faldt som funktion af tiden i årene efter ompløjning af græsmarkerne, men typen af græsmark havde kun ringe effekt på den efterfølgende nitratudvaskning. Tilførsel af kvæggylle til kornafgrøderne påvirkede nitratudvaskningen mere end græsmarkens forhistorie og fik i de fleste tilfælde den gennemsnitlige nitratkoncentration til at overstige grænseværdien i EU’s drikkevandsdirektiv. Formentlig blev store forskelle i N-input i afgræsningsmarkerne udlignet af betydelige, men variable tab under afgræsning. Mulighederne for yderligere at forbedre N-udnyttelsen efter ompløjning er begrænsende, når de her nævnte muligheder er implementeret. En yderligere øgning af N-udnyttelsen på malkekvægsbedrifter kan således primært opnås ved at forbedre N-udnyttelsen i afgræsningsmarkerne

Toward an Energy Efficient Language and Compiler for (Partially) Reversible Algorithms

We introduce a new programming language for expressing reversibility, Energy-Efficient Language (Eel), geared toward algorithm design and implementation. Eel is the first language to take advantage of a partially reversible computation model, where programs can be composed of both reversible and irreversible operations. In this model, irreversible operations cost energy for every bit of information created or destroyed. To handle programs of varying degrees of reversibility, Eel supports a log stack to automatically trade energy costs for space costs, and introduces many powerful control logic operators including protected conditional, general conditional, protected loops, and general loops. In this paper, we present the design and compiler for the three language levels of Eel along with an interpreter to simulate and annotate incurred energy costs of a program.Comment: 17 pages, 0 additional figures, pre-print to be published in The 8th Conference on Reversible Computing (RC2016

Photonic crystal resonator integrated in a microfluidic system

We report on a novel optofluidic system consisting of a silica-based 1D photonic crystal, integrated planar waveguides and electrically insulated fluidic channels. An array of pillars in a microfluidic channel designed for electrochromatography is used as a resonator for on-column label-free refractive index detection. The resonator was fabricated in a silicon oxynitride platform, to support electroosmotic flow, and operated at 1.55 microns. Different aqueous solutions of ethanol with refractive indices ranging from n = 1.3330 to 1.3616 were pumped into the column/resonator and the transmission spectra were recorded. Linear shifts of the resonant wavelengths yielded a maximum sensitivity of 480 nm/RIU and a minimum difference of 0.007 RIU was measured

Nonlinear dynamics induced by parallel and orthogonal optical injection in 1550 nm Vertical-Cavity Surface-Emitting Lasers (VCSELs)

We report a first experimental study of the nonlinear dynamics appearing in a 1550 nm single-mode VCSEL subject to parallel and to orthogonal optical injection. For the first time to our knowledge we report experimentally measured stability maps identifying the boundaries between regions of different nonlinear dynamics for both cases of polarized injection. A rich variety of nonlinear behaviours, including periodic (limit cycle, period doubling) and chaotic dynamics have been experimentally observed. ©2010 Optical Society of America

Immuno-fluorescent Labeling of Microtubules and Centrosomal Proteins in Ex Vivo Intestinal Tissue and 3D In Vitro Intestinal Organoids.

The advent of 3D in vitro organoids that mimic the in vivo tissue architecture and morphogenesis has greatly advanced the ability to study key biological questions in cell and developmental biology. In addition, organoids together with recent technical advances in gene editing and viral gene delivery promises to advance medical research and development of new drugs for treatment of diseases. Organoids grown in vitro in basement matrix provide powerful model systems for studying the behavior and function of various proteins and are well suited for live-imaging of fluorescent-tagged proteins. However, establishing the expression and localization of the endogenous proteins in ex vivo tissue and in in vitro organoids is important to verify the behavior of the tagged proteins. To this end we have developed and modified tissue isolation, fixation, and immuno-labeling protocols for localization of microtubules, centrosomal, and associated proteins in ex vivo intestinal tissue and in in vitro intestinal organoids. The aim was for the fixative to preserve the 3D architecture of the organoids/tissue while also preserving antibody antigenicity and enabling good penetration and clearance of fixative and antibodies. Exposure to cold depolymerizes all but stable microtubules and this was a key factor when modifying the various protocols. We found that increasing the ethylenediaminetetraacetic acid (EDTA) concentration from 3 mM to 30 mM gave efficient detachment of villi and crypts in the small intestine while 3 mM EDTA was sufficient for colonic crypts. The developed formaldehyde/methanol fixation protocol gave very good structural preservation while also preserving antigenicity for effective labeling of microtubules, actin, and the end-binding (EB) proteins. It also worked for the centrosomal protein ninein although the methanol protocol worked more consistently. We further established that fixation and immuno-labeling of microtubules and associated proteins could be achieved with organoids isolated from or remaining within the basement matrix