Peter Jensen

Unemployment and marital dissolution

This paper analyses the effects of unemployment on the probability of marital dissolution. Based on panel data for a sample of Danish married couples, we estimate a dynamic model for the probability of marital dissolution where we take into account the possible effects of unemployment for both spouses. We also control for other factors such as education, age, presence of children, place of residence, health and economic factors. The empirical results show that unemployment seems to be an important factor behind marital instability. However, only unemployment of the husband has an effect, and this effect is immediate.

Active labor market policies in Europe: Performance and perspectives

Executive summary.- and overview.- The European Employment Strategy.- An overview of Active Labor Market Policies.- The methodology of program evaluation.- Reports from selected EU25 member states.- The effectiveness of European ALMPs.- Conclusions and policy recommendations.

The response of youth unemployment to benefits, incentives, and sanctions

Abstract The decline in the youth unemployment rate in Denmark is nearly unique among OECD countries and merits study. In 1996, a radical labour market reform was implemented, the Youth Unemployment Programme (YUP), directed towards unemployed, low-educated youth. This paper analyses the effects of the implementation of the YUP. We investigate the duration of unemployment spells and the transition rates from unemployment to schooling and employment. Three effects are analysed: an announcement effect, a direct programme effect, and a sanction effect. We find that the YUP has been partially successful.

European Perspectives on the Adoption of Nonchemical Weed Management in Reduced-Tillage Systems for Arable Crops

Abstract Noninversion tillage with tine- or disc-based cultivations prior to crop establishment is the most common way of reducing tillage for arable cropping systems with small grain cereals, oilseed rape, and maize in Europe. However, new regulations on pesticide use might hinder further expansion of reduced-tillage systems. European agriculture is asked to become less dependent on pesticides and promote crop protection programs based on integrated pest management (IPM) principles. Conventional noninversion tillage systems rely entirely on the availability of glyphosate products, and herbicide consumption is mostly higher compared to plow-based cropping systems. Annual grass weeds and catchweed bedstraw often constitute the principal weed problems in noninversion tillage systems, and crop rotations concurrently have very high proportions of winter cereals. There is a need to redesign cropping systems to allow for more diversification of the crop rotations to combat these weed problems with less herbicide input. Cover crops, stubble management strategies, and tactics that strengthen crop growth relative to weed growth are also seen as important components in future IPM systems, but their impact in noninversion tillage systems needs validation. Direct mechanical weed control methods based on rotating weeding devices such as rotary hoes could become useful in reduced-tillage systems where more crop residues and less workable soils are more prevalent, but further development is needed for effective application. Owing to the frequent use of glyphosate in reduced-tillage systems, perennial weeds are not particularly problematic. However, results from organic cropping systems clearly reveal that desisting from glyphosate use inevitably leads to more problems with perennials, which need to be addressed in future research. Nomenclature: Catchweed bedstraw, Galium aparine L.; barley, Hordeum vulgare L.; maize, Zea mays L.; oilseed rape, Brassica napus L.; wheat, Triticum aestivum L. Resumen El cultivar sin inversión del suelo usando discos o picos, antes del establecimiento del cultivo, es la forma más común de reducir la labranza en sistemas de cultivos arables que incluyen cereales, colza y maíz en Europa. Sin embargo, nuevas regulaciones sobre el uso de plaguicidas podrían afectar la expansión de los sistemas de labranza reducida. La agricultura europea ha sido llamada a ser menos dependiente de los plaguicidas y a promover programas de protección de cultivos basados en los principios de manejo integrado de plagas (IPM). Los sistemas de labranza convencional sin inversión del suelo dependen totalmente de la disponibilidad de productos con glyphosate, y el consumo de herbicidas es mayoritariamente superior al compararse con sistemas de cultivo basados en el uso de arado. Malezas como zacates anuales y Galium aparine frecuentemente constituyen el principal problema de malezas en sistemas de labranza sin inversión del suelo y rotaciones de cultivos que además tienen proporciones muy altas de cereales de invierno. Existe la necesidad de rediseñar los sistemas de cultivos para permitir una mayor diversificación de las rotaciones de cultivos para así combatir estos problemas de malezas con un uso menor de herbicidas. Cultivos de cobertura, sistemas de manejo con residuos de cultivos, y tácticas que refuercen el crecimiento del cultivo en relación con el crecimiento de las malezas son también vistos como componentes importantes en los sistema IPM futuros, pero su impacto en los sistemas de labranza sin inversión del suelo necesita validación. Los métodos de control mecánico de malezas directo basados en implementos rotativos de deshierba, tales como azadones rotativos, han sido útiles en sistemas de labranza reducida donde la presencia de más residuos de cultivos y suelos menos trabajables son prevalentes, pero un mayor desarrollo de estos métodos es necesario para su aplicación efectiva. Debido al uso frecuente de glyphosate en sistemas de labranza reducida, las malezas perennes no son particularmente problemáticas. Sin embargo, resultados en sistemas de producción orgánicos han revelado claramente que el desistir del uso de glyphosate lleva inevitablemente a más problemas con malezas perennes, lo que necesita ser incluido en investigaciones futuras.

An excess of chromosome 1 breakpoints in male infertility.

In a search for potential infertility loci, which might be revealed by clustering of chromosomal breakpoints, we compiled 464 infertile males with a balanced rearrangement from Mendelian Cytogenetics Network database (MCNdb) and compared their karyotypes with those of a Danish nation-wide cohort. We excluded Robertsonian translocations, rearrangements involving sex chromosomes and common variants. We identified 10 autosomal bands, five of which were on chromosome 1, with a large excess of breakpoints in the infertility group. Some of these could potentially harbour a male-specific infertility locus. However, a general excess of breakpoints almost everywhere on chromosome 1 was observed among the infertile males: 26.5 versus 14.5% in the cohort. This excess was observed both for translocation and inversion carriers, especially pericentric inversions, both for published and unpublished cases, and was significantly associated with azoospermia. The largest number of breakpoints was reported in 1q21; FISH mapping of four of these breakpoints revealed that they did not involve the same region at the molecular level. We suggest that chromosome 1 harbours a critical domain whose integrity is essential for male fertility.

A Search Model Applied to the Transition from Education to Work

This paper presents the specification and estimation of a search model applied to the transition from education to work. The theoretical search model includes the possibility of variable search intensity. The empirical model with a reservation wage relation is estimated using maximum likelihood methods. A data set containing information on new law graduates is used for the estimation. Finally, the model is estimated for two separate subperiods to investigate the effects of market changes.

Basal‐Cell Subpopulations and Cell‐Cycle Kinetics In Human Epidermal Explant Cultures

Cultured human epidermal cells were studied by cell sorting and autoradiography after different 3H‐thymidine (3H‐dThd)‐labelling procedures and after labelling with DNA precursors that are incorporated via salvage or de novo pathways. It was shown that 3H‐dThd incorporation was the best measure of the rate of DNA replication. Dose‐response experiments with pulse and continuous labelling revealed that all S‐ and G2‐phase cells were cycling, whereas some 20% of the cells stayed in G1‐phase for long periods of time. Most, if not all of these cells were probably non‐proliferating differentiated keratinocytes. At least two subpopulations of S‐phase cells could be discriminated on the basis of the rate of incorporation of DNA precursors. the difference in precursor incorporation did not seem to be caused by differences in nucleotide metabolism but rather to reflect true differences in the rate of DNA replication. Continuous labelling experiments showed that these subpopulations also were apparent in the G1‐ and G2‐phases. Studies of the grain‐count distribution revealed that cells that appeared to move rapidly through the S‐phase moved slowly through the G2‐phase, and vice versa. Cells stained with acridine orange were subjected to a two‐parameter analysis in the cell sorter by simultaneous measurement of the DNA and RNA fluorescence. Autoradiography of sorted cells revealed that, on average, cells with low RNA contents incorporated 3H‐dThd at a higher rate than cells with high RNA contents.

Evidence That Mutations in the X-linked DDP Gene Cause Incompletely Penetrant and Variable Skewed X Inactivation

X chromosome inactivation results in the random transcriptional silencing of one of the two X chromosomes early in female development. After random inactivation, certain deleterious X-linked mutations can create a selective disadvantage for cells in which the mutation is on the active X chromosome, leading to X inactivation patterns with the mutation on the inactive X chromosome in nearly 100% of the individuals cells. In contrast to the homogeneous patterns of complete skewed inactivation noted for many X-linked disorders, here we describe a family segregating a mutation in the dystonia-deafness peptide (DDP) gene, in which female carriers show incompletely penetrant and variable X inactivation patterns in peripheral blood leukocytes, ranging between 50:50 and >95:5. To address the genetic basis for the unusual pattern of skewing in this family, we first mapped the locus responsible for the variable skewing to the proximal long arm (Xq12-q22) of the X chromosome (Z=5. 7, P=.002, LOD score 3.57), a region that includes both the DDP and the XIST genes. Examination of multiple cell types from women carrying a DDP mutation and of peripheral blood leukocytes from women from two unrelated families who carry different mutations in the DDP gene suggests that the skewed X inactivation is the result of selection against cells containing the mutant DDP gene on the active X chromosome, although skewing is apparently not as severe as that seen for many other deleterious X-linked mutations. Thus, DDP is an example of an X-linked gene for which mutations cause partial cell selection and thus incompletely skewed X inactivation in peripheral blood leukocytes.

Low Ca2+ stripping of differentiating cell layers in human epidermal cultures: An in vitro model of epidermal regeneration☆

An in vitro model of the epidermal regeneration process is described. Incubation of multilayered, keratinizing cultures of human epidermal cells in Ca2+-free medium for 72 h results in a complete stripping of all suprabasal layers. When the Ca2+ stripped cultures are refed normal Ca2+ medium a reproducible series of morphologic and cell kinetic changes takes place. It is suggested that these changes represent a general pattern of regeneration after epidermal wounding. After an initial lag phase the regenerative response is principally effected by a recruitment to the proliferating pool of cells with a high rate of DNA synthesis. The cells seem to be programmed to rapid differentiation. Studies with cholera toxin suggest that this adenylate cyclase-stimulating agent is able to induce significant changes in the regenerative process causing a prolonged, but less intense, proliferative response leading to lateral growth rather than to rapid differentiation.

Ring chromosome 20 with loss of telomeric sequences detected by multicolour PRINS

Brandt CA, Kierkegaard O, Hindkjær J, Jensen PKA, Pedersen S. Ring chromosome 20 with loss of telomeric sequences detected by multicolour PRINS.