Improved low cost ac-to-dc converter

Circuit converts an rms, ac voltage to a proportional dc voltage with good accuracy over a voltage range of approximately 6-1. It incorporates a pair of vacuum thermocouples in a dc feedback circuit

Rabl's model of the interphase chromosome arrangement tested in Chinise hamster cells by premature chromosome condensation and laser-UV-microbeam experiments

In 1885 Carl Rabl published his theory on the internal structure of the interphase nucleus. We have tested two predictions of this theory in fibroblasts grown in vitro from a female Chinese hamster, namely (1) the Rabl-orientation of interphase chromosomes and (2) the stability of the chromosome arrangement established in telophase throughout the subsequent interphase. Tests were carried out by premature chromosome condensation (PCC) and laser-UV-microirradiation of the interphase nucleus. Rabl-orientation of chromosomes was observed in G1 PCCs and G2 PCCs. The cell nucleus was microirradiated in G1 at one or two sites and pulse-labelled with 3H-thymidine for 2h. Cells were processed for autoradiography either immediately thereafter or after an additional growth period of 10 to 60h. Autoradiographs show unscheduled DNA synthesis (UDS) in the microirradiated nuclear part(s). The distribution of labelled chromatin was evaluated in autoradiographs from 1035 cells after microirradiation of a single nuclear site and from 253 cells after microirradiation of two sites. After 30 to 60h postincubation the labelled regions still appeared coherent although the average size of the labelled nuclear area fr increased from 14.2% (0h) to 26.5% (60h). The relative distance dr, i.e. the distance between two microirradiated sites divided by the diameter of the whole nucleus, showed a slight decrease with increasing incubation time. Nine metaphase figures were evaluated for UDS-label after microirradiation of the nuclear edge in G1. An average of 4.3 chromosomes per cell were labelled. Several chromosomes showed joint labelling of both distal chromosome arms including the telomeres, while the centromeric region was free from label. This label pattern is interpreted as the result of a V-shaped orientation of these particular chromosomes in the interphase nucleus with their telomeric regions close to each other at the nuclear edge. Our data support the tested predictions of the Rabl-model. Small time-dependent changes of the nuclear space occupied by single chromosomes and of their relative positions in the interphase nucleus seem possible, while the territorial organization of interphase chromosomes and their arrangement in general is maintained during interphase. The present limitations of the methods used for this study are discussed

Analysis of chromosome positions in the interphase nucleus of Chinese hamster cells by laser-UV-microirradiation experiments

Unsynchronized cells of an essentially diploid strain of female Chinese hamster cells derived from lung tissue (CHL) were laser-UV-microirradiated (=257 nm) in the nucleus either at its central part or at its periphery. After 7–9 h postincubation with 0.5 mM caffeine, chromosome preparations were made in situ. Twenty-one and 29 metaphase spreads, respectively, with partial chromosome shattering (PCS) obtained after micro-irradiation at these two nuclear sites, were Q-banded and analyzed in detail. A positive correlation was observed between the frequency of damage of chromosomes and both their DNA content and length at metaphase. No significant difference was observed between the frequencies of damage obtained for individual chromosomes at either site of microirradiation. The frequency of joint damage of homologous chromosomes was low as compared to nonhomologous ones. Considerable variation was noted in different cells in the combinations of jointly shattered chromosomes. Evidence which justifies an interpretation of these data in terms of an interphase arrangement of chromosome territories is discussed. Our data strongly argue against somatic pairing as a regular event, and suggest a considerable variability of chromosome positions in different nuclei. However, present data do not exclude the possibility of certain non-random chromosomal arrangements in CHL-nuclei. The interphase chromosome distribution revealed by these experiments is compared with centromere-centromere, centromere-center and angle analyses of metaphase spreads and the relationship between interphase and metaphase arrangements of chromosomes is discussed

Delineation of individual human chromosomes in metaphase and interphase cells by in situ suppression hybridization using recombinant DNA libraries

A method of in situ hybridization for visualizing individual human chromosomes from pter to qter, both in metaphase spreads and interphase nuclei, is reported. DNA inserts from a single chromosomal library are labeled with biotin and partially preannealed with a titrated amount of total human genomic DNA prior to hybridization with cellular or chromosomal preparations. The cross-hybridization of repetitive sequences to nontargeted chromosomes can be markedly suppressed under appropriate preannealing conditions. The remaining single-stranded DNA is hybridized to specimens of interest and detected with fluorescent or enzymelabeled avidin conjugates following post-hybridization washes. DNA inserts from recombinant libraries for chromosomes 1, 4, 7, 8, 13, 14, 18, 20, 21, 22, and X were assessed for their ability to decorate specifically their cognate chromosome; most libraries proved to be highly specific. Quantitative densitometric analyses indicated that the ratio of specific to nonspecific hybridization signal under optimal preannealing conditions was at least 8:1. Interphase nuclei showed a cohesive territorial organization of chromosomal domains, and laserscanning confocal fluorescence microscopy was used to aid the 3-D visualization of these domains. This method should be useful for both karyotypic studies and for the analysis of chromosome topography in interphase cells

Opting out and topping up reconsidered: Informal care under uncertain altruism

National audienceWe study the design of public long-term care (LTC) insurance when the altruism of informal caregivers is uncertain. We consider non-linear policies where the LTC transfer depends on the level of informal care, which is assumed to be observable, while children's altruism is not. Our policy encompasses two policies traditionally considered in the literature: topping up policies consisting of a transfer independent of informal care, and opting out policies entailing a positive transfer only if children fail to provide care. We show that both total and informal care should increase with the children's level of altruism. This is obtained under full and asymmetric information. Public LTC transfers, on the other hand, may be non-monotonic. Under asymmetric information, public LTC transfers are lower than their full information level for the parents whose children are the least altruistic, while it is distorted upward for the highest level of altruism. This is explained by the need to provide incentives to highly altruistic children. In contrast to both topping up and opting out policies, the implementing contract is always such that social care increases with informal care.Repenser les polices exclusives et non-exclusives : les soins informels dans un contexte de devouement aleatoire. Dans cet article, nous etudions le modele public d'assurance de soins de longue duree lorsque le devouement des aidants naturels est aleatoire. Nous nous interessons aux polices non-lineaires ou le transfert des soins de longue duree depend du niveau de soins informels, lequel etant supposement observable, a l'inverse du devouement des enfants, qui ne l'est pas. Notre police s'appuie sur les deux polices traditionnellement etudiees dans la litterature : les polices non-exclusives ( topping up policies ) consistant en un transfert independant des soins informels, et les polices exclusives ( opting out policies ) impliquant un transfert positif uniquement lorsque les enfants sont dans l'incapacite de fournir de l'aide. Nous montrons que l'ensemble des soins ainsi que les soins informels devraient augmenter proportionnellement au devouement des enfants, que l'information soit complete ou asymetrique. Les transferts publics de soins de longue duree, en revanche, peuvent s'averer non monotones. Dans un contexte d'information asymetrique, et pour les parents dont les enfants sont les moins devoues, les transferts publics de soins de longue duree sont inferieurs a ceux observes dans un contexte d'information complete; pour les parents dont les enfants sont les plus devoues, on observe une distorsion a la hausse. Ceci s'explique par la necessite de fournir des mesures incitatives aux enfants hautement devoues. Et contrairement aux polices exclusives et non-exclusives, le contrat d'execution est toujours tel que les soins sociaux augmentent proportionnellement aux soins informels