3,119 research outputs found
Design study for LANDSAT D attitude control system
A design and performance evaluation is presented for the LANDSAT D attitude control system (ACS). Control and configuration of the gimballed Ku-band antenna system for communication with the tracking and data relay satellite (TDRS). Control of the solar array drive considered part of the ACS is also addressed
Design study for LANDSAT-D attitude control system
The gimballed Ku-band antenna system for communication with TDRS was studied. By means of an error analysis it was demonstrated that the antenna cannot be open loop pointed to TDRS by an onboard programmer, but that an autotrack system was required. After some tradeoffs, a two-axis, azimuth-elevation type gimbal configuration was recommended for the antenna. It is shown that gimbal lock only occurs when LANDSAT-D is over water where a temporary loss of the communication link to TDRS is of no consequence. A preliminary gimbal control system design is also presented. A digital computer program was written that computes antenna gimbal angle profiles, assesses percent antenna beam interference with the solar array, and determines whether the spacecraft is over land or water, a lighted earth or a dark earth, and whether the spacecraft is in eclipse
Biaxial spin-nematic phase of two dimensional disordered rotor models and spin-one bosons in optical lattices
We show that the ground state of disordered rotor models with quadrupolar
interactions can exhibit biaxial nematic ordering in the disorder-averaged
sense. We present a mean-field analysis of the model and demonstrate that the
biaxial phase is stable against small quantum fluctuations. We point out the
possibility of experimental realization of such rotor models using ultracold
spin-one Bose atoms in a spin-dependent and disordered optical lattice in the
limit of a large number of atoms per site and also suggest an imaging
experiment to detect the biaxial nematicity in such systems.Comment: revtex file 7 pages, 2 figures, version published in PR
Extracellular sheath formation by Sphaeropsis hypodermia and association with its infection in elm trees
Nous avons observé le mode de développement de Sphaeropsis hypodermia (isolé d'une branche d'orme (Ulmus americana) atteinte d'un chancre) dans les milieux suivants : un milieu gélosé (PDA), un tissu essuie-tout (Kimwipes), des blocs de bois d'orme stérilisés à l'autoclave, et des ormes d'Amérique inoculés en serre. Des échantillons de chaque substrat ont été fixés pour les observations en microscopie photonique et en microscopie électronique avec du glutaraldéhyde et du tétroxyde d'osmium. Observés en microscopie électronique, les hyphes accolés au substrat étaient entourés d'une épaisse couche extracellulaire devenant circonscrite par des bandes rigides et contenant des corps opaques simples ou agrégés, ou des masses de matière opaque plus volumineuses dans le cas des blocs de bois d'orme. Sur celui-ci et sur le tissu Kimwipes, la couche extracellulaire s'étendait sur une distance appréciable, loin des cellules fongiques, et avait également pénétré les parois de cellules de parenchyme et des fibres, selon le cas. Dans les ormes inoculés, le champignon a rapidement produit des dommages notables dans les tissus du cambium et colonisé abondamment les régions de l'écorce et du xylème avoisinantes. La pénétration et la dégradation des parois cellulaires de l'écorce étaient marquées, en relation également avec de la matière opaque entourant les cellules du champignon. Cette matière ressemblait à celle liée aux cellules fongiques sur les milieux stérilisés. Bien que les cellules du xylème étaient généralement colonisées, des altérations pariétales n'étaient apparentes que dans les cellules récemment formées. En outre, le passage du champignon d'une cellule à l'autre à travers les parois n'a été observé que dans le cas des éléments de vaisseaux et des cellules de rayon. Concernant les fibres, seule y était visible une bande de matière filamenteuse dans les parois et liant les cellules fongiques présentes dans la lumière de ces fibres. En réponse à la dégradation de parois cellulaires liée à de la matière opaque, l'hypertrophie et l'hyperplasie des cellules du cambium et de l'écorce interne ont été observées, liées possiblement à la formation d'une barrière de protection. On discute du rôle possible de la couche extracellulaire des cellules fongiques in vivo et in vitro.Sphaeropsis hypodermia, isolated from a cankered American elm branch, was grown on agar medium (PDA), on autoclaved wiping paper (Kimwipes), and American elm (Ulmus americana) wood chips, or inoculated into greenhouse-grown American elm saplings. Samples from each treatment were double-fixed with glutaraldehyde and osmium tetroxide and examined with the light and the transmission electron microscopes. Ultrastructurally, the hyphae on PDA and inert substrates appeared surrounded by large extracellular sheaths which were delimited by rigid opaque bands of various thicknesses. The sheaths extended appreciable distances from the fungal cells, as evidenced by their adherence to rigid substrates. Individual or aggregated opaque bodies, even as large masses on elm wood chips, were the main components of the sheath. This opaque material was often associated with penetration and ruptures of the wood cells. Inoculated into elm trees, the fungus rapidly caused pronounced alterations of cambial tissues and colonized the adjoining bark and xylem cells. The prominent penetration and breakdown of the inner and outer bark cells by the fungus were associated with opaque material, particularly in cortical fibres. The material was structurally similar to the sheath formed on the rigid sterilized substrates. In the xylem, only the walls of the recently deposited cells were visibly altered, and although mature fibres were generally colonized, the passage of the fungus from one fibre to another was rarely observed, contrary to the passage from vessel and ray cells to adjoining cells. In that instance, only bands of opaque material present in the walls of fibres were connected with fungal cells in their lumen. In the inner bark and cambial regions, cell hypertrophy and hyperplasia occurred next to host walls that were altered and contained similar opaque material. The extracellular sheath of S. hypodermia under in vitro conditions and the opaque material associated with host wall alterations in vivo are considered to be analogous
Puppetry as an art therapy technique with emotionally disturbed children
Puppetry has long been used as a diagnostic and therapeutic technique with emotionally disturbed children and has been well documented in the literature. Limited research has been done on the creation of puppets in therapy or on the use of puppetry in art therapy. This thesis outlines methods of using puppetry as a group art therapy technique with emotionally disturbed children. The technique includes both diagnostic and therapeutic uses of puppetry. The psycholo-oical rationale of puppetry is reviewed. Two art therapy qroups of emotionally disturbed children were treated for ten weeks using puppetry. The children made various types of puppets and spontaneous puppet play was encouraged. Material from these sessions is examined in terms of psychodynamics in relation to individual case histories. This thesis proposes that puppetry is a valuable art therapy technique with emotionally disturbed children. Recommendations for further research in this area are included.M.A., Art Therapy -- Hahnemann University, 198
Metformin-mediated increase in DICER1 regulates microRNA expression and cellular senescence
Metformin, an oral hypoglycemic agent, has been used for
decades to treat type 2 diabetes mellitus. Recent studies indicate
that mice treated with metformin live longer and have fewer
manifestations of age-related chronic disease. However, the
molecular mechanisms underlying this phenotype are unknown.
Here, we show that metformin treatment increases the levels of
the microRNA-processing protein DICER1 in mice and in humans
with diabetes mellitus. Our results indicate that metformin
upregulates DICER1 through a post-transcriptional mechanism
involving the RNA-binding protein AUF1. Treatment with metformin
altered the subcellular localization of AUF1, disrupting its
interaction with DICER1 mRNA and rendering DICER1 mRNA
stable, allowing DICER1 to accumulate. Consistent with the role
of DICER1 in the biogenesis of microRNAs, we found differential
patterns of microRNA expression in mice treated with metformin
or caloric restriction, two proven life-extending interventions.
Interestingly, several microRNAs previously associated with
senescence and aging, including miR-20a, miR-34a, miR-130a,
miR-106b, miR-125, and let-7c, were found elevated. In agreement
with these findings, treatment with metformin decreased
cellular senescence in several senescence models in a DICER1-
dependent manner. Metformin lowered p16 and p21 protein
levels and the abundance of inflammatory cytokines and oncogenes
that are hallmarks of the senescence-associated secretory
phenotype (SASP). These data lead us to hypothesize that
changes in DICER1 levels may be important for organismal aging
and to propose that interventions that upregulate DICER1
expression (e.g., metformin) may offer new pharmacotherapeutic
approaches for age-related disease
Suction-controlled experiments on Boom clay
The understanding of the thermo-hydro-mechanical behaviour of a clay barrier is needed for the prediction of its
final in situ properties after the hydration and thermal transient in a radioactive waste repository.
As part of the CEC 1990-1994 R&D programme on radioactive waste management and storage, the CEA (Fr),
CIEMAT (Sp). ENRESA (Sp). SCK CEN (B). UPC (Sp) and UWCC (UK) have carried out a joint project on
unsaturated clay behaviour (Volckaert et al.. 1996). The aim of the study is to analyse and model the behaviour of a
clay-based engineered barrier during its hydration phase under real repository conditions. The hydro-mechanical and
thermo-hydraulic models developed in this project have been coupled to describe stress/strain behaviour, moisture
migration and heat transfer. A thermo-hydraulic model has also been coupled to a geochemical code to describe the
migration and formation of chemical species.
In this project. suction-controlled experiments have been performed on Boom clay (B), FoCa clay (Fr) and Almeria
bentonite (Sp). The aim of these experiments is to test the validity of the interpretive model developed by Alonso and
Gens (Alonso et al., 1990). and to build a database of unsaturated clay thermo-hydro-mechanical parameters. Such
a database can then be used for validation exercises in which in situ experiments are simulated.
The Boom clay is a moderately swelling clay of Rupellian age. It is studied at the SCK. CEN in Belgium as a
potential host rock for a radioactive waste repository. In this paper, suction-controlled experiments carried out on
Boom clay by SCK CEN are described. SCK CEN has performed experiments to measure the relation between
suction, water content and temperature and the relation between suction, stress and deformation. The applied suctioncontrol
techniques and experimental setups are detailed. The results of these experiments are discussed in the
perspective of the model of Alonso and Gens. The influence of temperature on water uptake was rather small. The
measured swelling-collapse behaviour can be explained by the Alonso and Gens model.Peer Reviewe
Foresterie, aménagement du territoire et télédétection
L article envisage les perspectives offertes par les données satellitaires spot-1 dans les domaines de l aménagement du territoire et de la foresterie. L intérêt majeur de la télédétection en foresterie réside dans la possibilité d obtenir des vues synoptiques sur des territoires importants, dans celle de mise à jour fréquente (6 à 13 mois par exemple), les données peuvent être délivrées à l utilisateur directement sous forme numérique, ce qui autorise des combinaisons avec des données externes (administratives, techniques, scientifiques)
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