Tomography of high-redshift clusters with OSIRIS

High-redshift clusters of galaxies are amongst the largest cosmic structures. Their properties and evolution are key ingredients to our understanding of cosmology: to study the growth of structure from the inhomogeneities of the cosmic microwave background; the processes of galaxy formation, evolution, and differentiation; and to measure the cosmological parameters (through their interaction with the geometry of the universe, the age estimates of their component galaxies, or the measurement of the amount of matter locked in their potential wells). However, not much is yet known about the properties of clusters at redshifts of cosmological interest. We propose here a radically new method to study large samples of cluster galaxies using microslits to perform spectroscopy of huge numbers of objects in single fields in a narrow spectral range-chosen to fit an emission line at the cluster redshift. Our objective is to obtain spectroscopy in a very restricted wavelength range (~100 A in width) of several thousands of objects for each single 8x8 square arcmin field. Approximately 100 of them will be identified as cluster emission-line objects and will yield basic measurements of the dynamics and the star formation in the cluster (that figure applies to a cluster at z~0.50, and becomes ~40 and ~20 for clusters at z~0.75 and z~1.00 respectively). This is a pioneering approach that, once proven, will be followed in combination with photometric redshift techniques and applied to other astrophysical problems.Comment: 4 pages, 3 figures. Proceedings of "Science with the GTC", Granada (Spain), February 2002, RMxAA in pres

Osteogenic preconditioning in perfusion bioreactors improves vascularization and bone formation by human bone marrow aspirates.

Cell-derived extracellular matrix (ECM) provides a niche to promote osteogenic differentiation, cell adhesion, survival, and trophic factor secretion. To determine whether osteogenic preconditioning would improve the bone-forming potential of unfractionated bone marrow aspirate (BMA), we perfused cells on ECM-coated scaffolds to generate naïve and preconditioned constructs, respectively. The composition of cells selected from BMA was distinct on each scaffold. Naïve constructs exhibited robust proangiogenic potential in vitro, while preconditioned scaffolds contained more mesenchymal stem/stromal cells (MSCs) and endothelial cells (ECs) and exhibited an osteogenic phenotype. Upon implantation into an orthotopic calvarial defect, BMA-derived ECs were present in vessels in preconditioned implants, resulting in robust perfusion and greater vessel density over the first 14 days compared to naïve implants. After 10 weeks, human ECs and differentiated MSCs were detected in de novo tissues derived from naïve and preconditioned scaffolds. These results demonstrate that bioreactor-based preconditioning augments the bone-forming potential of BMA

Crystal structure of cobalt hydroxide carbonate Co2CO3(OH)(2): density functional theory and X-ray diffraction investigation

The cobalt carbonate hydroxide Co2CO3(OH)2 is a technologically important solid which is used as a precursor for the synthesis of cobalt oxides in a wide range of applications. It also has relevance as a potential immobilizer of the toxic element cobalt in the natural environment, but its detailed crystal structure is so far unknown. The structure of Co2CO3(OH)2 has now been investigated using density functional theory (DFT) simulations and powder X-ray diffraction (PXRD) measurements on samples synthesized via deposition from aqueous solution. Two possible monoclinic phases are considered, with closely related but symmetrically different crystal structures, based on those of the minerals malachite [Cu2CO3(OH)2] and rosasite [Cu1.5Zn0.5CO3(OH)2], as well as an orthorhombic phase that can be seen as a common parent structure for the two monoclinic phases, and a triclinic phase with the structure of the mineral kolwezite [Cu1.34Co0.66CO3(OH)2]. The DFT simulations predict that the rosasite-like and malachite-like phases are two different local minima of the potential energy landscape for Co2CO3(OH)2 and are practically degenerate in energy, while the orthorhombic and triclinic structures are unstable and experience barrierless transformations to the malachite phase upon relaxation. The best fit to the PXRD data is obtained using a rosasite model [monoclinic with space group P1121/n and cell parameters a = 3.1408 (4) Å, b = 12.2914 (17) Å, c = 9.3311 (16) Å and γ = 82.299 (16)°]. However, some features of the PXRD pattern are still not well accounted for by this refinement and the residual parameters are relatively poor. The relationship between the rosasite and malachite phases of Co2CO3(OH)2 is discussed and it is shown that they can be seen as polytypes. Based on the similar calculated stabilities of these two polytypes, it is speculated that some level of stacking disorder could account for the poor fit of the PXRD data. The possibility that Co2CO3(OH)2 could crystallize, under different growth conditions, as either rosasite or malachite, or even as a stacking-disordered phase intermediate between the two, requires further investigation

Early onset sebaceous carcinoma

<p>Abstract</p> <p>Background</p> <p>Ocular sebaceous carcinoma can masquerade as benign lesions resulting in delay of diagnosis. Early recognition is even more difficult in young patients where the disease rarely occurs. Here, we provide a clinicopathological correlation of ocular sebaceous carcinoma in a young individual lacking history of hereditary cancer or immunosuppression.</p> <p>Findings</p> <p>A detailed histopathological study including <it>p53 </it>DNA sequencing was performed on an aggressive sebaceous carcinoma presenting in a healthy 32 year-old Caucasian woman. She had no history of retinoblastoma, evidence for a hereditary cancer syndrome, or radiation therapy. However, she potentially was at risk for excessive UV light exposure. A detailed review of the literature is also provided.</p> <p>A moderately well differentiated sebaceous carcinoma was established histopathologically arising from the meibomian gland of the upper eyelid. In most areas, the cytoplasm contained small but distinct Oil-red-O positive vacuoles. Direct sequencing of <it>p53 </it>identified a G:C→A:T mutation at a dipyrimidine site. The mutation results in substitution of arginine for the highly conserved glycine at residue 199 located at the p53 dimer-dimer interface. Energy minimization structural modeling predicts that G199R will neutralize negative charges contributed by nearby inter- and intramonomeric glutamate residues.</p> <p>Discussion</p> <p>This study points to the importance of recognizing that sebaceous carcinoma can occur in young patients with no evidence for hereditary cancer risk or radiation therapy. The G199R substitution is anticipated to alter the stability of the p53 tetrameric complex. The role of UV light in the etiology of sebaceous carcinoma deserves further study. Our findings, taken together with those of others, suggest that different environmental factors could lead to the development of sebaceous carcinoma in different patients.</p

Module structure of interphotoreceptor retinoid-binding protein (IRBP) may provide bases for its complex role in the visual cycle – structure/function study of Xenopus IRBP

<p>Abstract</p> <p>Background</p> <p>Interphotoreceptor retinoid-binding protein's (IRBP) remarkable module structure may be critical to its role in mediating the transport of all-<it>trans and 11-cis </it>retinol, and 11-<it>cis </it>retinal between rods, cones, RPE and Müller cells during the visual cycle. We isolated cDNAs for <it>Xenopus </it>IRBP, and expressed and purified its individual modules, module combinations, and the full-length polypeptide. Binding of all-<it>trans </it>retinol, 11-cis retinal and 9-(9-anthroyloxy) stearic acid were characterized by fluorescence spectroscopy monitoring ligand-fluorescence enhancement, quenching of endogenous protein fluorescence, and energy transfer. Finally, the X-ray crystal structure of module-2 was used to predict the location of the ligand-binding sites, and compare their structures among modules using homology modeling.</p> <p>Results</p> <p>The full-length <it>Xenopus </it>IRBP cDNA codes for a polypeptide of 1,197 amino acid residues beginning with a signal peptide followed by four homologous modules each ~300 amino acid residues in length. Modules 1 and 3 are more closely related to each other than either is to modules 2 and 4. Modules 1 and 4 are most similar to the N- and C-terminal modules of the two module IRBP of teleosts. Our data are consistent with the model that vertebrate IRBPs arose through two genetic duplication events, but that the middle two modules were lost during the evolution of the ray finned fish. The sequence of the expressed full-length IRBP was confirmed by liquid chromatography-tandem mass spectrometry. The recombinant full-length <it>Xenopus </it>IRBP bound all-<it>trans </it>retinol and 11-<it>cis </it>retinaldehyde at 3 to 4 sites with <it>K</it>_<it>d</it>'s of 0.2 to 0.3 μM, and was active in protecting all-<it>trans </it>retinol from degradation. Module 2 showed selectivity for all-<it>trans </it>retinol over 11-cis retinaldehyde. The binding data are correlated to the results of docking of all-<it>trans</it>-retinol to the crystal structure of <it>Xenopus </it>module 2 suggesting two ligand-binding sites. However, homology modeling of modules 1, 3 and 4 indicate that both sites may not be available for binding of ligands in all four modules.</p> <p>Conclusion</p> <p>Although its four modules are homologous and each capable of supporting ligand-binding activity, structural differences between their ligand-binding domains, and interactions between the modules themselves will be critical to understanding IRBP's complex role in the visual cycle.</p

Corrosion activity and solubility in polar oils of three bis(trifluoromethylsulfonyl) imide/bis(trifluoromethylsulfonyl) amide ([NTF2]) anion-based ionic liquids.

The corrosion behaviour and solubility of three bis(trifluoromethylsulfonyl)amide1 ([NTf2]) anion-based ionic liquids: 1-dodecyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([C12MIM][NTf2]), tributylmethylammonium bis(trifluoromethylsulfonyl)amide ([N4441][NTf2]), and methyltrioctylammonium bis(trifluoromethylsulfonyl)amide ([N1888][NTf2]), as a component in a mixture with different base oils were analysed. Six polar oils suitable for use in lubrication were utilized as base oil. Solubility tests were performed by using turbidimetry, and corrosion was checked at 4 v/v% by examining the roughness and chemical composition of the surface after 21 days. The results showed that long carbon chains in the cation improve the solubility greatly in diesters and slightly in polyolesters. Corrosion was not detected at this concentration