Nitrogen isotope analysis of ammonium and glycine

Stable isotope techniques can be used as a tool in nitrogen cycling studies of different ecosystems. The studies are based on measurement of the heavy (15N)- to- light (14N) isotopic ratios of nitrogen in different biospheric pools. Isotope ratio mass spectrometry (IRMS) is the most precise technique to use for analysis of nitrogen isotopic ratios. This thesis deals with the development of methods for compound-specific nitrogen isotope analysis of ammonium and glycine in aqueous solutions and soil extracts using Gas Chromatography - Combustion (GC-C) - IRMS. For ammonium, three different techniques were developed: equilibrium headspace analysis, solid phase microextraction (SPME) and the purge and trap (P & T) technique, which were all based on conversion of ammonium to ammonia with subsequent separation of ammonia for analysis. In the SPME and P & T approaches, custom-made absorbents were used for pre-concentration, followed by thermal desorption into the GC-C-IRMS system. For the equilibrium headspace technique, high precision measurements of the nitrogen isotopic ratio were obtained for concentrations above 420 mg N L-1. With further improvements and the use of suitable equipment, the method has the potential to be used for solutions containing ammonium in the low mg N L-1 range. The SPME technique increased the sensitivity by a factor of » 3 compared to the headspace technique, but was less precise. In addition, the NafionÒ material used for absorption showed a memory effect in the desorption step. With the P & T technique a large variation in the measured isotopic value was observed (using solutions containing 2 mg N L-1) which was due to a non-quantitative thermal desorption. However, with further improvements, the P & T technique has the potential to be used for samples containing below 1.0 µg N, which is a much lower amount than that possible with any method used today. A method for determination of the nitrogen isotopic ratio in free glycine in soil extracts was also developed. By a combination of sample pre-concentration and Isotope Dilution Mass Spectrometry (IDMS), it was possible to determine isotopic ratio in soil extracts with a glycine concentration of only 3 µM (0.042 mg N L-1). The precision obtained was sufficient for use with tracer studies and was higher by an order of magnitude than the precision obtained with conventional GC-MS

An Analysis of Immigrants’ Participation in Adult Education in Sweden

The purpose of this paper is to analyze to what extent different groups of immigrants in Sweden take part in two adult education measures, the Adult Education Initiative (AEI) and Labor Market Training (LMT). A multinomial logit model is estimated using register data. The results show that the probability to participate in the AEI, instead of being openly unemployed, in general is lower among immigrants than among natives with two Swedish born parents. However, differences in the probability to participate in the AEI exist between groups with different region of heritage. Some evidence is also found indicating that the probability to participate in the AEI is higher for more recent immigrant cohorts than for earlier. Moreover, for some region of heritage groups, the results indicate that naturalized immigrants have a higher probability to participate in the AEI than non-naturalized immigrants. The probability to participate in LMT, instead of being openly unemployed, is in general higher among immigrants than among natives with two Swedish born parents. Crudely, one might say that the probability to participate tends to be higher in region of heritage groups with a weaker position in the labor market. In line with what was shown for the AEI, there is also a weak tendency that more recently arrived immigrants have a higher probability to participate than earlier immigrants. No large differences concerning the probability to participate in LMT, instead of being openly unemployed, are found between naturalized immigrants and non-naturalized immigrants.Immigration; Adult Education; Discrete Regression and Qualitative Choice Models

Psychological Traits and Earnings Differences Among Men: A Study of Second - Generation Immigrants in Sweden

The purpose of this study is to analyse the impact of psychological traits on earnings differentials between second-generation immigrants and individuals with native-born parents. The study is based on the cohort of men born in 1973 and residing in Sweden in December 1990. In this paper we use an indicator of psychological ability measured in connection to the military enrolment test in Sweden. The results show that the measure of psychological traits is an important determinant of earnings at the age of 30. Using an Oaxaca-Blinder decomposition we find that the earnings differences between second-generation immigrants and individuals with native born parents to a large part are explained by differences in endowments of psychological traits.Earnings differentials; psychological traits; military enrolment test; secondgeneration immigrants; Oaxaca-Blinder decomposition

Civil Returns of Military Training: A Study of Young Men in Sweden

The purpose of this paper is to study the effect of military training on earnings for young men in Sweden. The analysis is based on the cohort of men born in 1973. The 1973 cohort was conscripted during a time of rapid change in the Swedish security policy and substantial cutdowns of the armed forces. As a consequence, a relatively large part of the cohort was assigned a service category after the enlistment test but one third of these individuals were never conscripted. We argue that these organizational changes along with the set of important background variables that are available makes it possible to rely on selection on observables. A strong result is that military training has a positive effect on annual earnings at the age of 30 for the group in the private category that subsequently do not obtain an high educational level.Earnings; Conscription; Enlistment test; Military training

Leasing vs. buying equipment

"Traditionally farmers have found it to their advantage to credit finance rather than lease farm equipment. There are, however, situations where leasing is a viable alternative. Lease plans are available for larger machinery items, irrigation systems, and semi-portable buildings such as farrowing houses or calf barns. This guide reviews the important factors that you should consider in evaluating a financial lease. The guide also shows how to compare the cost of a lease with the cost of a creditfinanced purchase. The term lessor is used to refer to the company or firm who owns the equipment. The term lessee refers to the user of the leased equipment."--First page.Norlin Hein (Department of Agricultural Economics, College-of Agriculture)New 8/80/10

Expression Profiling of Blood Vessels in Pericyte Deficiency and Diabetes

The kidney glomerulus is essential for the filtration of waste products from the blood into the urine and in controlling the volume and composition of body fluids. Injury to the glomerulus can lead to altered glomerular filtration rate, proteinuria, thickening of the glomerular basement membrane (GBM) and accumulation of mesangial cell matrix. The injuries can occur due to primary kidney diseases or as a secondary effect of other diseases such as diabetes mellitus. The blood-brain barrier (BBB) differs in many ways from of the glomerular filtration barrier. While glomerular endothelial cells are fenestrated and highly permeable, the endothelial cells of the blood-brain barrier are continuous and held together by tight junctions. Passage across the BBB is tightly controlled and serves to protect the neuronal tissue of the central nervous system from fluctuations in hormones, nutrients, metabolites and other substances in the blood. The targeted deletion of either platelet-derived growth factor-B (PDGF-B) or PDGFR- β is embryonic lethal due to cardiovascular complications and lead to a failure in recruiting pericytes to the developing vasculature and mesangial cells into the glomerulus. In paper I we investigated the role of endothelium-derived PDGF-B in the recruitment of pericytes and mesangial cells using a mouse model with a targeted conditional deletion of PDGF-B in endothelial cells. We found that the phenotype mimics that of the null mutation, but is much milder. Thus the endothelium appears to be the main source of PDGF-B in the vasculature. In the kidney, the initial deficiency of glomerular mesangial cells normalized soon after birth and later led to a very light albuminuria and enlargement of the glomeruli. To increase our knowledge of the glomerular transcriptome we constructed a cDNA array from isolated mouse glomeruli. In paper II we used it to identify a number of novel glomerular transcripts. In a series of experiments these transcripts were assigned to specific cell types and characterized as podocyte or mesangial cell/juxtaglomerular markers. Further study on podocyte marker Foxc2 revealed a role in podocyte differentiation and glomerular development. In paper III we used several pericyte deficient mouse models to elucidate the role of pericytes in the integrity of the BBB. We found a correlation between the degree of pericyte deficiency and the extravasation of injected tracers across the BBB via macromolecular trancytosis, for the first time in vivo demonstrating the importance of pericytes in maintaining the BBB function. To gain insight into the transcriptional changes behind diabetes-related glomerular injury, we analyzed kidney function and gene expression in the db/db mouse, a model of type 2 diabetes. We found increased expression of genes relating to the infiltration of monocytes/macrophages into the glomerulus, changes in expression of genes involved in the composition of the GBM and the extracellular matrix, as well as in signal transduction and growth factor expression. We also noted strong and consistent upregulation of Ym-1, a marker for alternatively activated macrophages (aaMac). Further analysis of our data set revealed that expression of several markers for aaMac were upregulated, while markers for classically activated macrophages remained unaltered

Fatigue Behaviour of LVL Subjected to Repeated Shear Stresses.

The fatigue behavior of laminated veneer lumber (Douglas-fir) subjected to shearstress has been studied. The static shear strength of specimens, 37 by 102 by 406 mm was established through a three point bending test over a span of 305 mm. Four series of specimens were subjected to a cyclic load history with peak loads ranging from 95 to 80 percent of the static strength. The duration of each load cycle was approximately 32 seconds. A stress-level verses (log) number of cycles diagram was produced to show the fatigue behavior. The load-level was calculated from the static strength using the assumption of equal rank. A least square regression analysis was made and was found to fit the S-N data well. The lowest load-level tested in this research was approximately 70 percent. At this load-level the specimen survived close to 3000 cycles

Grönt spår

En förtätning av staden ställer hårda krav på de grönområden som finns, och de förväntas hålla en hög kvalitet av vad gäller såväl rekreation som möjliggörande av biologisk mångfald. Då gröna utemiljöer skapas i staden är det av stor vikt att dessa kan erbjuda rekreativa och ekologiskt intressanta miljöer på såväl kort- som lång sikt. Målet med detta examensarbete har varit att göra ett gestaltningsförslag med fokus på värdefulla utemiljöer för rekreation och biologisk mångfald under platsens olika livsfaser, där vegetationens dynamiska potential utnyttjas. I arbetet undersöks hur ett gestaltningsförslag av den planerade grannskapsparken i Järnvägsverkstäderna, Kirseberg i Malmö, kan möta dessa mål. Inför gestaltningsförslaget har en bakgrundsstudie av platsen Järnvägsverkstäderna gjorts, och det har skett inläsning av litteratur kring ämnen som vegetationsdynamik och vegetationsgestaltning. För att kunna uppnå både lång- och kortsiktiga värden har vegetationens dynamik utnyttjas och använts i förslaget, och vegetationens föränderlighet har setts som en styrka. Ett bevarande av befintlig vegetation är av stor vikt för att kunna uppnå direkta ekologiska och rekreativa värden. Vidare kan det konstateras att en god förståelse för byggprocess och etappfaser är fördelaktigt för att kunna skapa en attraktiv utemiljö under en plats olika livsfaser.Densification of urban environments has led to higher demands placed upon pre-existing green areas within cities. These green spaces are expected to simualtaneously function as recreational areas as well as to sustain biodiversity. As green spaces are created in the city, it is important that they can offer recreational and ecologically interesting environments, for both the near and distant future. The goal of this thesis has been to produce a design proposal with focus upon an outdoor space that accounts for both recreational values and biodiversity during the site’s various life stages, and were the dynamic potential of vegetation is utilized. In particular, this study uses a design proposal to examines how the planned urban park at Järnvägsverkstäderna, Kirseberg in Malmö could be a place which offers an interesting and ecologically valuable outdoor environment in the short and long term. To achive this, a background study of Järnvägsverkstäderna has been carried out together with research surrounding related topics of vegetation dynamics and vegetation design. In order to meet both the long- and short-term values, vegetation dynamics have been utilized in the proposal, and the dynamics of the vegetation have been seen as a strengths. Preservation of existing vegetation is of great importance in order to achieve immediate ecological and recreational values. Furthermore, it can be regarded that a good understanding of the construction processes and developing stages can be beneficial to successfully create an attractive outdoor environment throughout the site’s life cycle