Influence of Cu adatoms on the molecular assembly of 4,4'-bipyridine on Cu(111).

The formation of highly organized structures based on two ligands with pyridyl functionalities, 4,4'-bipyridine (BPY) and 1,4-di(4,4''-pyridyl) benzene (BPYB), and Cu adatoms on the Cu(111) surface has been studied with low temperature and variable temperature scanning tunneling microscopy (STM) and first-principles calculations. We show that the formation of a highly organized adlayer built from adatom-molecule and molecule-molecule units strongly depends on the number of mobile Cu atoms on the surface. While a high concentration of Cu adatoms (high adatom/BPY ratio, ≥1) leads systematically to the formation of organometallic nanolines, their absence (low adatom/BPY ratio, ≈0) gives a compact self-assembled molecular network, and more specifically hydrogen-bond networks (HBN) with BPY molecules organized in a T-shaped fashion. Alternatively, an intermediate concentration of Cu adatoms (0 < adatom/BPY < 1) allows the formation of a well-organized and compact structure where both organometallic and HBN components coexist. Although STM images cannot clearly reveal the presence of Cu adatoms within the organometallic moiety, the bonding of BPY to a single or two Cu adatoms can be clearly identified by scanning tunneling spectroscopy (STS), and is supported by Density Functional Theory (DFT) results. Additional STM simulations suggest that the relative position of the Cu adatom with respect to the organic ligands just above has a significant impact on its detection by STM. This study exemplifies the prominent role of metallic adatoms on the formation of a complex organometallic network and should open more rational practices to optimize the formation of these supramolecular networks.

Electronic properties of self-assembled trimesic acid monolayer on graphene.

The adsorption of trimesic acid (TMA) on a graphene surface has been studied with density functional theory. By considering the adsorption of a single TMA molecule on different sites on graphene, we have been able to perform a detailed analysis of the equilibrium geometry, charge transfer, electronic properties in terms of density of states and band structure, and finally scanning tunneling microscopy simulations on those simple systems. The results for isolated adsorption were then compared to the behavior of the TMA unit within two different self-assembled monolayers. Our results indicate that structural deformations of TMA may significantly contribute to the magnitude of p-doping and band gap opening in graphene. The formation of a hydrogen bonding network within the assembly improves the stability of the adlayer, but its adhesion on graphene is significantly reduced. The magnitude of p-doping in graphene per TMA unit remains nearly constant from the isolated to the assembled systems, but the magnitude of the band gap opening appears to be strongly correlated with the breaking of symmetry of π-states of graphene by the TMA patterning on the surface. Our results suggest that polymorphism in self-assembled adlayers could be used to tune and control the electronic properties of graphene.

Effects of long jumps, reversible aggregation, and Meyer-Neldel rule on submonolayer epitaxial growth.

We demonstrate, using kinetic Monte Carlo simulations of submonolayer epitaxial growth, that long jumps and reversible aggregation have a major impact on the evolution of island morphologies. Long jumps are responsible for a supra-Arrhenius behavior of the effective diffusion coefficient as the attachment and detachment kinetics give rise to a bimodal island size distribution that depends on temperature and long jump extent limits. As the islands density increases with temperature, the average size of stable islands reaches a maximum before decreasing. We have also observed that the diffusion coefficient cannot be used alone to predict the evolution of island sizes and morphologies, the relative rate of each process having a major importance. Our theoretical developments are of direct relevance for materials systems such as Au, Pd, Ag, Cu, Ni, H/Si , H/W(110), Co/Ru , and Co/Ru(S), that are known for exhibiting a compensation effect that cannot be contained within experimental uncertainties.

Age-related mechanical properties of human skin: an in vivo study.

We have investigated in vivo how various viscoelastic parameters that describe the mechanical properties of the human skin may vary with age. Accordingly, we have used a mechanical device that records the torsional extensibility of the skin. When submitted to a low torque, the time-response curve of the skin affords the determination of the immediate extensibility (UE), the immediate recovery (UR), the viscoelastic part of the deformation (UV), the elastic recovery (UR/UE), and the creep relaxation time (tau). Because the skin thickness varies with age and primarily governs the mechanical properties, it was measured through an ultrasound technique at the same sites (forearm) where the torque was applied. The results show that the skin maintains its thickness and extensibility up to the seventh decade as opposed to its elasticity or recovery capacities, which decrease from an early age. The viscous part of the deformation is constant through life, whereas the creep relaxation time decreases linearily with age. Except for skin thickness, no differences in these parameters between men and women were detected. The significance of these results are discussed in terms of structure alterations. The determination of the elastic recovery (UR/UE) appears to be a parameter of choice for illustrating skin aging.

[Green hair: clinical, chemical and epidemiologic study. Apropos of a case]. / Les cheveux verts: étude clinique, chimique et épidémiologique. A propos d'un cas.

A 36-year-old blond woman suddenly developed green tinted hair following exposure to swimming pool water. This was the first green discoloration she noticed, although she had been an active swimmer for several years. Clinical examination showed green tinting toward the distal ends of the most superficial strands of hair. The copper content of plucked green hair measured by atomic absorption was elevated to 3,900 ppm and the copper concentration in water from the swimming pool implicated was 9.94 ppm. Following renewal, the latter value decreased to 107 ppb. Hair examination under polarizing light was normal, and a scanning electronmicroscopic study of hair samples showed a total loss of cuticle with micropits scattered over the hair shaft surface mimicking a "dead tree trunk". Epidemiological investigations showed that the increased copper content of swimming pool water was due to added algaecides without adequate replacement of the water. Hair damage resulting from repeated waving and/or bleaching of the hair turns out to be an important factor in the deposition of copper by inducing an increase in keratin content of cysteic acid and related anionic sulfonate groups which participate in copper adsorption. On the ocassion of this case-report, epidemiological data published by others, together with the chemical and therapeutic aspects of green hair are reviewed.

Impact of nucleation on step-meandering instabilities during step-flow growth on vicinal surfaces.

Step-meandering instabilities can manifest during step-flow growth on vicinal surfaces [Bales and Zangwill, Phys. Rev. B 41, 5500 (1990); Pierre-Louis, D'Orsogna, and Einstein, Phys. Rev. Lett. 82, 3661 (1999)]. A phase diagram based on the various growth regimes of a vicinal surface allows us to study the impact of nucleation on these meanders and to predict a meandering instability caused by the nucleation and the coalescence of both islands and steps. Using an accelerated kinetic Monte Carlo method, we find that the coalescence of islands with steps produces large protrusions and deep ripples and that the resulting meandering instability is reinforced by the growth of the islands at almost the same positions from one monolayer to the other. A coarsening phenomenon occurs for the instability wavelength until mounds appear, favored by a large Ehrlich-Schwoebel barrier. Such a meandering instability could be exploited for periodic self-assembly.

Anisotropic growth of the thiophene-based layer on Si(111)-B.

The formation of large assemblies on the Si(111)-B surface is discussed with the help of STM simulations and DFT calculations. Although highly regular assemblies of DTB10B along the Si row direction are observed, the existence of two herringbone isomers introduces a lower periodicity within the 2D molecular network. The formation of herringbone units is explained by weak intermolecular interactions while the 1D assembling depends mainly on the interactions of the C10 side chains with the Si(111)-B surface.

Embolización de riñón poliquístico: una alternativa menos invasiva a la nefrectomía pre-trasplante / Embolization of polycystic kidney: a less invasive alternative to pretransplant nephrectomy

La embolización arterial de riñón poliquístico, en candidatos a trasplante renal, es una técnica recientemente descrita que pudiese servir como alternativa a la nefrectomía a objeto de generar el espacio suficiente para el injerto. Materiales y Métodos: Presentamos el caso de un paciente varón de 57 años con enfermedad renal crónica secundario a enfermedad renal poliquística familiar autosómica dominante en hemodiálisis. Los riñones ocupaban completamente el abdomen y pelvis. Se le realizó embolización del riñón derecho y se controló con Tomografía Axial Computada de abdomen y pelvis sin contraste cada 3 meses. Resultados: El procedimiento se realizó sin complicaciones, salvo el intenso dolor lumbar posterior al procedimiento que requirió altas dosis de analgesia endovenosa. Se logró una disminución del volumen renal de un 46 por ciento en 6 meses, creando así espacio suficiente para el alojamiento del injerto renal. A los 9 meses se realizó el trasplante, evolucionando con adecuada función del injerto. Conclusión: La embolización arterial renal es una técnica efectiva, poco invasiva y con baja morbilidad, la cual puede ser utilizada para la disminución del volumen renal, en pacientes con riñones poliquísticos, a objeto de crear suficiente espacio para un trasplante renal...

Renal arterial embolization of polycystic kidneys in renal transplant candidates has been recently described as an alternative to nephrectomy for generating enough space for the renal graft. Materials and Methods: We present the case of a 57 year old male patient, with chronic renal failure in hemodialysis, secondary to autosomal dominant polycystic kidney disease. The cystic kidneys completely occupied the abdomen and pelvis leaving no space for a renal transplant. Right renal arterial embolization was performed. The patient was followed up with unenhanced computed tomography every 3 months. Results: Right renal embolization was performed without complications, except the severe low back pain, which required high doses of intravenous analgesia. Renal volume decreased by 46 percent in 6 months, making enough space for the renal graft. Nine months after embolization, renal transplant was carried out on the right iliac fossa with no complications and with immediate graft function. Conclusion: Renal arterial embolization is an effective, less invasive and safer technique that can be used to reduce renal volume and make enough space for a renal transplant...

Desmoplastic trichoepithelioma nosology. Reappraisal about a case developed on a varicella scar.

We report the case of a 51-year-old woman who presented with a progressive elevation of the border of an old varicella scar. The lesion which was clinically diagnosed as a basal cell carcinoma turned out to be a typical desmoplastic trichoepithelioma. The development of desmoplastic trichoepithelioma in an area of scarring has not been previously reported. The nosology of this tumor is discussed with particular emphasis on its possible relationship to morphoeic basal cell carcinoma, thus questioning it as a true tumor sui generis.

A new technique for the evaluation of cosmetics effect on mechanical properties of stratum corneum and epidermis in vitro.

Synopsis The mechanical properties of stratum corneum and epidermis have been measured in vitro and a dispersity of approximately 30% to 50% between samples from the same donor has been found. To overcome such a limitation, a technique was developed in order to compare the mechanical properties of the same skin sample before and after treatment. The chosen parameter (initial slope of the stress-strain curve) appeared to be influenced by the topical application of products. A different time response was found with stratum corneum and epidermis reflecting their structural differences. Une nouvelle technique d'evaluation de l'effet des produits cosmétique sur les propriétés mécaniques du stratum corneum et de l'épiderme humains (etude in vitro).

Treatment of scleroderma with oral 1,25-dihydroxyvitamin D3: evaluation of skin involvement using non-invasive techniques. Results of an open prospective trial.

1,25-dihydroxycholecalciferol (1,25 (OH)2 D3) causes dose-dependent inhibition of fibroblast growth and collagen synthesis and has numerous immunoregulatory activities. We assessed the effects of oral 1,25 (OH)2 D3 in the treatment of patients with systemic sclerosis (SS). Eleven patients with SS entered an open prospective study. Oral 1,25(OH)2 D3 was given at a mean dose of 1.75 micrograms/day. The effects of the treatment were evaluated using clinical examination and physical measurements. After the treatment period (6 months to 3 years), a significant improvement, as compared with baseline values, was observed. No serious side-effects were observed. These results suggest that high-dose 1,25 (OH)2 D3 may be a useful therapeutic agent for scleroderma.

Localized scleroderma--response to 1,25-dihydroxyvitamin D3.

1,25-Dihydroxyvitamin D3 [1,25(OH)2 D3] may be an immunomodulatory drug which could have a role in controlling collagen deposition, and inducing reversal of fibrosis in some tissues. These observations prompted a study of the possible use of this hormone for the treatment of scleroderma. A 35-year-old woman, who had been suffering from localized scleroderma for 2 years, was given oral 1,25(OH)2 D3 for 6 months. The effects of the treatment were evaluated using clinical and physical measurements (skin thickness, extensibility properties of the skin). The evolution of the patient's condition during the 6-month therapy suggests that 1,25(OH)2 D3 is beneficial in localized scleroderma. The mechanisms of action are discussed in relation to the literature, which suggests both immunoregulatory and inhibitory effects on fibroblast growth.