Graphene catalyzes the reversible formation of a C-C bond between two molecules.

Carbon deposits are well-known inhibitors of transition metal catalysts. In contrast to this undesirable behavior, here we show that epitaxial graphene grown on Ru(0001) promotes the reversible formation of a C-C bond between -CH2CN and 7,7,8,8-tetracyano-p-quinodimethane (TCNQ). The catalytic role of graphene is multifaceted: First, it allows for an efficient charge transfer between the surface and the reactants, thus favoring changes in carbon hybridization; second, it holds the reactants in place and makes them reactive. The reaction is fully reversible by injecting electrons with an STM tip on the empty molecular orbitals of the product. The making and breaking of the C-C bond is accompanied by the switching off and on of a Kondo resonance, so that the system can be viewed as a reversible magnetic switch controlled by a chemical reaction.

Observation of Localized Vibrational Modes of Graphene Nanodomes by Inelastic Atom Scattering.

Inelastic helium atom scattering (HAS) is suitable to determine low-energy (few meV) vibrations spatially localized on structures in the nanometer range. This is illustrated for the nanodomes that appear often on graphene (Gr) epitaxially grown on single crystal metal surfaces. The nature of the inelastic losses observed in Gr/Ru(0001) and Gr/Cu/Ru(0001) has been clarified by intercalation of Cu below the Gr monolayer, which decouples the Gr layer from the Ru substrate and changes substantially the out-of-plane, flexural phonon dispersion of epitaxial Gr, while maintaining the nanodomes and their localized vibrations. He diffraction proves that the Cu-intercalated Gr layer is well ordered structurally, while scanning tunneling microscopy reveals the persistence of the (slightly modified) periodic array of Gr nanodomes. A simple model explains the order of magnitude of the energy losses associated with the Gr nanodomes and their size dependence. The dispersionless, low-energy phonon branches may radically alter the transport of heat in intercalated Gr.

Controlling the spin of co atoms on pt(111) by hydrogen adsorption.

We investigate the effect of H adsorption on the magnetic properties of individual Co atoms on Pt(111) with scanning tunneling microscopy. For pristine Co atoms, we detect no inelastic features in the tunnel spectra. Conversely, CoH and CoH2 show a number of low-energy vibrational features in their differential conductance identified by isotope substitution. Only the fcc-adsorbed species present conductance steps of magnetic origin, with a field splitting identifying their effective spin as Seff=2 for CoH and 3/2 for CoH2. The exposure to H2 and desorption through tunnel electrons allow the reversible control of the spin in half-integer steps. Because of the presence of the surface, the hydrogen-induced spin increase is opposite to the spin sequence of CoHn molecules in the gas phase.

PCR protocol for detection of Vibrio ordalii by amplification of the vohB (hemolysin) gene.

Vibrio ordalii is the causative agent of atypical vibriosis and has the potential to cause severe losses in salmonid aquaculture. To prevent and control outbreaks, a rapid, reproducible, sensitive, and effective diagnostic method is needed. We evaluated a new conventional polymerase chain reaction (PCR) and real-time PCR (qPCR) protocol using a primer set (VohB_Fw-VohB_Rv) designed to amplify a 112 bp fragment flanking the vohB gene (coding for hemolysin production), against 24 V. ordalii strains isolated from different fish species, the V. ordalii type strain, and 42 representative related and unrelated bacterial species. The primer set was species-specific, recognizing all V. ordalii strains evaluated, with no cross-reaction with the other bacterial species. A sensitivity of 103 copies of the vohB gene was obtained with a standard curve. When the VohB_Fw-VohB_Rv qPCR protocol was applied to Atlantic salmon seeded tissues (kidney, liver, spleen, and muscle), the detection limit ranged from 5.27 × 102 to 4.13 × 103 V. ordalii CFU ml-1, i.e. 62 to 145 copies of the vohB gene, using the previously calculated standard curve. The conventional PCR also detected V. ordalii, but the total reaction time was 1 h longer. When the qPCR protocol was applied to naturally infected cage-cultured Atlantic salmon samples, 5 of 8 fish tested positive for V. ordalii, but only one of them was diagnosed as positive by direct cultivation on agar. We conclude that the PCR protocol evaluated is fast, specific, and sensitive enough to detect V. ordalii in infected tissues and is an important tool for secure diagnosis of atypical vibriosis, and is therefore helpful for the control of the disease through the prompt detection within fish populations.

Effect of different degrees of impaired glucose metabolism on the expression of inflammatory markers in monocytes of patients with atherosclerosis.

Inflammatory markers are elevated in type 2 diabetic patients (DP) and may predict the development of type 2 diabetes. Our aims were to analyze differences in the expression of inflammatory and immunological molecules between DP and healthy subjects and to investigate whether glycemic control might prevent the overexpression of inflammatory markers in DP. Twenty-two DP with advanced atherosclerosis and eight healthy blood donors were included. DP were classified as well (HbA1c ≤ 6.5) or poorly controlled (HbA1c > 6.5). In "in vitro" studies, monocytes were exposed to low (5.5 mM) or high glucose (26 mM) concentrations in the absence or presence of insulin. Expression profiling of 14 inflammatory genes was analyzed using TLDA analysis. "In vivo" results show that monocytes from DP had increased levels of monocyte chemoattractant protein (MCP-1) and interleukin 6 (IL6) and lower levels of Toll-like receptor 2 (TLR2) mRNA than healthy subjects. Well-controlled DP had lower levels of IL-6 than poorly controlled DP, suggesting that glycemic control may prevent IL6 mRNA alterations associated with diabetes. "In vitro" results demonstrate that glucose directly and significantly induced MCP-1 and IL6 and reduced TLR2 mRNA expression. Insulin at high dose (100 IU/ml) dramatically enhanced the upregulatory effects of glucose on MCP-1 and IL-6 and reduced per se TLR2 mRNA expression. MCP-1, IL-6 and TLR2 are key inflammatory players altered in monocytes from type 2 DP. Both hyperinsulinemia and hyperglycemia contribute to alter the expression of these genes. The glycemic control only significantly prevented IL6 overexpression in this group of patients.

Magnetic moment and anisotropy of individual Co atoms on graphene.

We report on the magnetic properties of single Co atoms on graphene on Pt(111). By means of scanning tunneling microscopy spin-excitation spectroscopy, we infer a magnetic anisotropy of K=-8.1 meV with out-of-plane hard axis and a magnetic moment of 2.2µ(B). Co adsorbs on the sixfold graphene hollow site. Upon hydrogen adsorption, three differently hydrogenated species are identified. Their magnetic properties are very different from those of clean Co. Ab initio calculations support our results and reveal that the large magnetic anisotropy stems from strong ligand field effects due to the interaction between Co and graphene orbitals.

Reactivity of periodically rippled graphene grown on Ru(0001).

We report here the reactivity of epitaxial graphene islands and complete monolayers on Ru(0001) towards molecular oxygen and air. The graphene is prepared by thermal decomposition of ethylene molecules pre-adsorbed on an Ru(0001) surface in an ultra-high vacuum chamber. The graphene layer presents a periodically rippled structure that is dictated by the misfit between graphene and Ru(0001) lattice parameters. The periodic ripples produce spatial charge redistribution in the graphene and modifies its electronic structure around the Fermi level. In order to investigate the reactivity of graphene we expose graphene islands to a partial pressure of oxygen and following the evolution of the surface by STM during the exposure. For the exposure to air we removed the sample from the UHV chamber and we re-introduce it after several hours, taking STM images before and after. The surface areas not covered by the graphene islands present a dramatic change but the graphene structure, even the borders of the islands, remain intact. In the case of a complete graphene monolayer the exposure to oxygen or to air does not affect or destroy the rippled structure of the graphene monolayer.

The role of the amorphous phase in the re-crystallization process of cold-crystallized poly(ethylene terephthalate).

The process of re-crystallization in poly(ethylene terephthalate) is studied by means of X-ray diffraction (SAXS and WAXS) and dynamical mechanical thermal analysis. Samples cold-crystallized for 9h at the temperatures T(c) = 100°C and T (c) = 160°C, i.e. in the middle of the alpha relaxation region and close to its upper bound, respectively, are analyzed. During heating from room temperature, a structural rearrangement of the stacks is always found at T (r) approximately T (c) + 20°C. This process is characterized by a decrease of the linear crystallinity, irrespective of T(c); on the other hand, the WAXS crystallinity never increases with T below T(c+30)°C. The lamellar thickness in the low-T(c) sample decreases significantly after the structural transition, whereas in the high-T(c) sample the lamellar thickness remains almost unchanged. In both, high- and low-T(c), the interlamellar thickness increases above T(r). Moreover, the high-T(c) sample shows a lower rate of decrease of the mechanical performance with increasing T as the threshold T(r) is crossed. This result is interpreted in terms of the formation of rigid amorphous domains where the chains are partially oriented. The presence of these domains would determine i) the stabilization of the crystalline lamellae from the thermodynamic point of view and ii) the increase of the elastic modulus of the amorphous interlamellar regions. This idea is discussed by resorting to a phase diagram. An estimation of the chemical-potential increase of the interlamellar amorphous regions, due to the enhancement of the structural constraints hindering segmental mobility, is offered. Finally, previous calculations developed within the framework of the Gaussian chain model (F.J. Baltá Calleja et al., Phys. Rev. B 75, 224201 (2007)) are used here to estimate the degree of chain orientation induced by the structural transition of the stacks.

Periodically rippled graphene: growth and spatially resolved electronic structure.

We grow epitaxial graphene monolayers on Ru(0001) that cover uniformly the substrate over lateral distances larger than several microns. The weakly coupled graphene monolayer is periodically rippled and it shows charge inhomogeneities in the charge distribution. Real space measurements by scanning tunneling spectroscopy reveal the existence of electron pockets at the higher parts of the ripples, as predicted by a simple theoretical model. We also visualize the geometric and electronic structure of edges of graphene nanoislands.

Real-space direct visualization of the layer-dependent roughening transition in nanometer-thick Pb films.

By means of variable-temperature scanning tunneling microscopy and spectroscopy we studied the thickness-dependent roughening temperature of Pb films grown on Cu(111), whose electronic structure and total energy is controlled by quantum well states created by the spatial confinement of electrons. Large scale STM images are employed to quantify the layer population, i.e., the fraction of the surface area covered by different Pb thicknesses, directly in the real space as a function of temperature. The roughening temperature oscillates repeatedly with bilayer periodicity plus a longer beating period, mirroring the thickness dependence of surface energy calculations. Conditions have been found to stabilize at 300 K Pb films of particular magic thicknesses, atomically flat over microns.

Contrast reversal and shape changes of atomic adsorbates measured with scanning tunneling microscopy.

Systematic, quantitative comparisons between scanning tunneling microscopy (STM) experiments and first principles simulations of O(2 x 2)/Ru(0001) have been performed. The shape of the atomic adsorbates in the images depends strongly on the tunneling resistance and changes reversibly from circular (high resistance) to triangular (low resistance). In addition, after adsorption of oxygen on the STM tip we observe a contrast reversal on the surface, confirmed by extensive numerical simulations.

On the relationship between crystalline structure and amorphous phase dynamics during isothermal crystallization of bacterial poly(3-hydroxybutyrate-co-3-hydroxyvalerate) copolymers.

The isothermal crystallization process of a poly(3-hydroxybutyrate-co-3-hydroxyvalerate) copolymer, P(HB-co-HV) with a HB/HV ratio 78/22 was investigated by simultaneous small-angle X-ray scattering (SAXS), wide-angle X-ray scattering (WAXS), and dielectric spectroscopy (DS). By use of this experimental setup (SWD), we have obtained simultaneous information about changes occurring in both the crystalline and the amorphous phases during crystallization. By using the Havriliak-Negami formalism to analyze the dielectric relaxation data, a strong dependence of the relaxation curve shape with the development of the crystalline phase was found. However, in this particular copolymer, the developing crystalline domains do not affect significantly the average segmental mobility in the amorphous phase. This effect is discussed in the light of the enrichment of amorphous phase by HV comonomer units during primary crystallization, hindering the secondary crystallization processes. Results support the hypothesis that the decrease of the physical-aging-like behavior, observed in P(HB-co-HV) copolymers as the amount of HV increases, can be attributed to the progressive inhibition of secondary crystallization mechanisms.

Induced mutagenic effects in the nucleotide excision repair deficient Drosophila mutant mus201(D1), expressing a truncated XPG protein.

Defects in nucleotide excision repair (NER) as defined by the UV sensitivity of xeroderma pigmentosum (XP), Cockayne syndrome (CS) and trichothiodystrophy (TTD) patients has lead to the identification of most of the genes involved: XPA through XPG, CSA and CSB. Whereas XP patients often show an increased risk for skin cancer after exposure to sunlight, this is not the case for patients with CS and TTD. Several CS patients have been shown to carry a defect in the XPG gene. The XPG, a structure specific endonuclease makes the incision 3' of damage and is also involved in the subsequent 5'incision during the NER process. In addition, XPG plays a role in the removal of oxidative DNA damage. The Drosophila XPG gene was isolated and based on the molecular defect of a spontaneous (insertion) and an EMS induced mutant, it was shown that a mutated XPG is responsible for the Drosophila mutagen-sensitive mutants mus201. One of these mutants, mus201(D1) has been used extensively in studies of the effects and mechanisms of many chemical mutagens as well as X-rays. The results of these studies are discussed in the light of the finding that mus201p is the Drosophila homologue of XPG.

Modulation of the toxic and mutagenic effects induced by methyl methanesulfonate in Chinese hamster ovary cells by overexpression of the rat N-alkylpurine-DNA glycosylase.

Exposure of mammalian cells to alkylating agents causes transfer of alkyl groups to N- as well as O-atoms of DNA bases. Especially the O-alkylated G and T bases have strong mutagenic properties, since they are capable of mispairing during replication. The mutagenic potential of N-alkylbases is less clear although specific base excision repair (BER) pathways exist which remove those lesions from the DNA. We investigated the relative contribution of N-alkylations to mutation induction at the Hprt gene in cultured Chinese hamster ovary cells (CHO). To this end BER activity in CHO cells was modulated by introduction of an expression vector carrying the rat N-alkylpurine-DNA glycosylase (APDG) gene, which codes for a glycosylase that is able to remove 3-methyladenine and 7-methylguanine from DNA thereby generating apurinic sites. Upon selection of a CHO clone which 10 times overproduced APDG compared to control CHO cells, mutation induction, the mutational spectrum, and cell survival were determined in both cell lines following treatment with methyl methanesulfonate (MMS). The results show that over-expression of APDG renders CHO cells more sensitive for mutation induction as well as cytotoxicity induced by MMS. The involvement of apurinic sites in induction of base pair changes at positions where 3-methyladenine was induced is inferred from the observation that the mutational spectrum of MMS-induced mutations in APDG-CHO cells showed twice as much base pair changes at AT base pairs (33.3%) compared to the spectrum of MMS-induced mutations in CHO-control cells (15.8%).

Se debe indicar la cirugía en la rotura traumática de la aorta torácica? / Is surgery indicated in traumatic rupture of the thoracic aorta?

Objetivo: El momento ideal para indicar la cirugía en un paciente con rotura traumática de aorta torácica sigue siendo controvertido. Parece, a tenor de las últimas publicaciones, que existe una opinión favorable a demorar en lo posible dicha indicación. Revisamos con este objetivo nuestra experiencia. Material y métodos: Nuestra casuística es de 13 pacientes. Once fueron operados, 8 de ellos con carácter emergente y 3 programados a los 4, 15 y 120 días. Dos pacientes recibieron sólo tratamiento médico. Resultados: Cinco pacientes fallecieron (mortalidad operatoria del 38 por ciento). Tres de estos fallecidos fueron por fracaso multiorgánico a los 3, 10 y 40 días respectivamente. Estos tres pacientes fueron dos de ellos los que siguieron tratamiento médico y el tercero uno de los operados emergentemente. Los otros dos exitus fueron por shock hemorrágico. La mortalidad de los pacientes operados programadamente fue del 0 por ciento y la de los operados emergentemente del 37 por ciento. Conclusiones: Aunque en la mortalidad hospitalaria intervienen diversos factores, como grado e importancia de las lesiones asociadas, técnica quirúrgica, etc., consideramos que el tiempo ideal de indicación quirúrgica debe ser lo más precoz posible si no existen lesiones cerebrales o abdominales graves y el paciente está estabilizado metabólica y hemodinámicamente. Aunque existen diversas posibilidades de corrección, nos inclinamos por usar by pass parcial izquierdo lo que permite mejor protección medular y desarrollo de la técnica quirúrgica. Generalmente hemos usado la interposición de un injerto protésico

Se debe indicar la cirugía en la rotura traumática de la aorta torácica? / Is surgery indicated in traumatic rupture of the thoracic aorta?

Objetivo: El momento ideal para indicar la cirugía en un paciente con rotura traumática de aorta torácica sigue siendo controvertido. Parece, a tenor de las últimas publicaciones, que existe una opinión favorable a demorar en lo posible dicha indicación. Revisamos con este objetivo nuestra experiencia. Material y métodos: Nuestra casuística es de 13 pacientes. Once fueron operados, 8 de ellos con carácter emergente y 3 programados a los 4, 15 y 120 días. Dos pacientes recibieron sólo tratamiento médico. Resultados: Cinco pacientes fallecieron (mortalidad operatoria del 38 por ciento). Tres de estos fallecidos fueron por fracaso multiorgánico a los 3, 10 y 40 días respectivamente. Estos tres pacientes fueron dos de ellos los que siguieron tratamiento médico y el tercero uno de los operados emergentemente. Los otros dos exitus fueron por shock hemorrágico. La mortalidad de los pacientes operados programadamente fue del 0 por ciento y la de los operados emergentemente del 37 por ciento. Conclusiones: Aunque en la mortalidad hospitalaria intervienen diversos factores, como grado e importancia de las lesiones asociadas, técnica quirúrgica, etc., consideramos que el tiempo ideal de indicación quirúrgica debe ser lo más precoz posible si no existen lesiones cerebrales o abdominales graves y el paciente está estabilizado metabólica y hemodinámicamente. Aunque existen diversas posibilidades de corrección, nos inclinamos por usar by pass parcial izquierdo lo que permite mejor protección medular y desarrollo de la técnica quirúrgica. Generalmente hemos usado la interposición de un injerto protésico (AU)

Mitral valve surgery through right thoracotomy.

UNLABELLED: Two years ago we had, for technical reason to resuscitate right thoracotomy (RT) to approach the mitral valve. Since then we have used it in 23 patients. 18 of them had had at least one operation through a medium sternotomy. In 5 cases the right approach was electively used, as first choice to repair or replace the mitral valve. Intracardiac surgery was performed routinely with moderate hypothermia and controlled ventricular fibrillation with the aorta unclamped. Only in one case, an unexpected aortic incompetence forced us to cross-clamp the aorta and replace the valve using crystalloid cold cardioplegia. 14 patients underwent mitral valve replacement. In 5 cases a leaking mitral prosthesis was successfully reattached and in 4 cases the native valve was repaired. 2 patients died (9%) for reasons unrelated to the technique. We did not have any case of air embolism. CONCLUSION: 1) RT is very useful to approach the mitral valve, specially in patients who previously had: a) several sternotomies, b) postoperative mediastinitis, specially if treated by omentoplasty, c) coronary artery bypass; 2) the good view to the mitral valve obtained with the aorta unclamped, make us think if the mitral repair should elective done through this approach.

Comparative evaluation of pentoxifylline, buflomedil, and nifedipine in the treatment of intermittent claudication of the lower limbs.

In the light of the current controversy surrounding the use of hemorheologic and vasodilator drugs in the treatment of peripheral arteriosclerosis, a comparative study was designed in order to evaluate the efficacy of pentoxifylline, buflomedil, and nifedipine in 45 patients with peripheral arterial disease (Fontaine stage II). The patients in this prospective randomized study were divided into three groups: 15 patients received pentoxifylline treatment (1,200 mg/day), 15 were treated with buflomedil (600 mg/day), and 15 with nifedipine (60 mg/day). Response to treatment was assessed at the start of the study and after forty-five and ninety days, by clinical examination, Doppler test, strain test, and digital occlusion plethysmography using a strain gauge ring. Pentoxifylline was significantly more effective (P < 0.05) than buflomedil and nifedipine at ninety days in improving walking performance, resting toe pressure, resting and postexercise ankle/brachial pressure ratio, and basal/postischemic toe-pulse ratio. Significant differences within groups were also noted for initial claudication, toe peak-flow time, pulse reappearance time (PRT/2), and maximum postischemic flow time, together with significant intergroup variables. In conclusion, pentoxifylline proved more effective than the other drugs tested in: 1. improving distal pressure and resting microcirculatory blood flow; 2. increasing postexercise distal flow, ratios, and pressures and enabling faster recuperation of basal pulse rates; 3. increasing initial claudication distance in the strain test within the test group and achieving a greater absolute subjective claudication distance than that obtained using the other treatments.

Operative management of a persistent sciatic artery aneurysm.

A 60-year-old man with a painful pulsatile mass approximately 8 cm in diameter in the right buttock was diagnosed using angiography as having a complete unilateral persistent sciatic artery aneurysm. The lesion was obliterated by proximal and distal ligation of the sciatic artery at the pelvis and the adductor magnus canal. A femoropopliteal bypass was performed with inverted autologous saphenous vein. The residual mass was subsequently drained because of persistent symptoms. Postoperative recovery was good.