Hierarchical Self-Assembly of Halogen-Bonded Block Copolymer Complexes into Upright Cylindrical Domains

Self-assembly of block copolymers into well-defined, ordered arrangements of chemically distinct domains is a reliable strategy for preparing tailored nanostructures. Microphase separation results from the system, minimizing repulsive interactions between dissimilar blocks and maximizing attractive interactions between similar blocks. Supramolecular methods have also achieved this separation by introducing small-molecule additives binding specifically to one block by noncovalent interactions. Here, we use halogen bonding as a supramolecular tool that directs the hierarchical self-assembly of low-molecular-weight perfluorinated molecules and diblock copolymers. Microphase separation results in a lamellar-within-cylindrical arrangement and promotes upright cylindrical alignment in films upon rapid casting and without further annealing. Such cylindrical domains with internal lamellar self-assemblies can be cleaved by solvent treatment of bulk films, resulting in separated and segmented cylindrical micelles stabilized by halogen-bond-based supramolecular crosslinks. These features, alongside the reversible nature of halogen bonding, provide a robust modular approach for nanofabricatio

Demonstration experiments for solid state physics using a table top mechanical Stirling refrigerator

Liquid free cryogenic devices are acquiring importance in basic science and engineering. But they can also lead to improvements in teaching low temperature an solid state physics to graduate students and specialists. Most of the devices are relatively expensive, but small sized equipment is slowly becoming available. Here, we have designed several simple experiments which can be performed using a small Stirling refrigerator. We discuss the measurement of the critical current and temperature of a bulk YBa2Cu3O(7-d) (YBCO) sample, the observation of the levitation of a magnet over a YBCO disk when cooled below the critical temperature and the observation of a phase transition using ac calorimetry. The equipment can be easily handled by students, and also used to teach the principles of liquid free cooling

Aves y peces como bioindicadores de las alteraciones debidas al turismo en manantiales de zonas semiáridas en México: bases para la gestión

Tourist disturbance in semi–arid springs was analysed; birds and fish were selected as bioindicators. Media Luna spring is the biggest and most spatially complex system in the region, with the highest biodiversity levels and tourist use. Areas with the highest bird species richness and abundances showed highest structural heterogeneity and least direct human impact. No differences in species richness of fish were observed between sectors and the most abundant species were found in the sectors least perturbed by human activity. Factors that explained the bird distribution were the species´ tolerance to the effects of direct tourism (noise and direct presence of people) and habitat quality, mainly riparian vegetation. Aquatic vegetation condition was very important for fish. Six bird species and two fish species were relevant as indicators of the habitat quality related to human impact. Anthropic disturbance such as tree plantation favoured some bird species, whereas aquatic vegetation removal was favourable for some fish species, such as the endemic Cichlasoma bartoni, however, both types of disturbance were unfavourable for other species; riparian vegetation removal was negative for both groups. Controlled tourism promotes good conditions for C. bartoni establishment. Efficient conservation measures such as limiting touristic distribution are necessary for all species, especially for the fish community, in order to conserve biodiversity in general. Key words: Wetlands, Species distribution, Threatened species, Endemism, Habitat loss, Spatial heterogeneity, Bioindicators.Para analizar las alteraciones por el turismo en manantiales de zonas semiáridas se utilizaron aves y peces como bioindicadores. Se seleccionó el manantial de la Media Luna por ser el más grande y complejo, y por incluir la más alta biodiversidad y el mayor impacto turístico en la zona. Los sectores con alta diversidad y abundancias de aves fueron los que tienen la mayor heterogeneidad estructural y menor impacto humano directo. Las mayores abundancias de peces se encontraron en los sectores menos perturbados sin diferencias para la riqueza de especies. Los factores que explicaron la distribución de las aves fueron la tolerancia de las especies a los efectos directos del turismo (ruido y presencia directa de gente) y la calidad del hábitat, principalmente la vegetación ribereña. La condición de la vegetación acuática fue muy importante para los peces. Seis especies de aves y dos de peces fueron relevantes como indicadores de la calidad del hábitat en función del impacto humano. Las alteraciones antrópicas tales como la plantación de árboles favoreció a algunas especies de aves mientras que la eliminación de la vegetación acuática fue favorable para algunos peces como el endémico Cichlasoma bartoni, pero estas alteraciones fueron negativas para otras especies; la eliminación de la vegetación ribereña tuvo efectos negativos para ambos grupos. El turismo controlado crea condiciones favorables para C. bartoni. Para la conservación de la biodiversidad en general, se requieren medidas eficientes de conservación tales como la restricción geográfica del turismo especialmente importante para la comunidad de peces. Palabras clave: Humedales, Distribución de las especies, Especies amenazadas, Endemismos, Pérdida de hábitat, Heterogeneidad espacial, Bioindicadores

Regional-scale vegetation heterogeneity in northeastern Patagonia: Environmental and spatial components

Our aim was to describe vegetation heterogeneity at a regional scale in northeastern Patagonia and to identify the environmental variables associated to it. The study area encompasses 13 144 km2 and is characterized by a mixture of species typical of Patagonian steppes and Monte Desert. We performed 48 vegetation relevés, which were randomly assigned to a training set and to a validation set (32 and 16 relevés, respectively). Training set was subjected to cluster analysis, which allowed the identification of two plant communities one related to Patagonian steppes and another to the Monte desert. We derived 3 attributes of the seasonal curve of the NDVI as indicators of ecosystem function: the seasonal amplitude (SA), the date of the maximum (DOM), and the large seasonal integral (LSI). We explored the relationship between NDVI attributes and communities by classification tree analysis. LSI was the strongest predictor among NDVI attributes, separating both communities without misclassification errors. Patagonian steppes occupy areas with higher LSI. The partial RDA analysis explained 38.1% of total data variation, of which 16.5% was ascribed to environment, 7.9% to space, and 13.7% to spatial component of environment. Patagonian steppes are closer to the coast, in areas exhibiting higher annual precipitation and lower annual temperature range than Monte deserts. Our results indicate the occurrence of two plant communities in the study area and highlight the significance of climatic variables to explain their spatial distribution. As most scenarios of future climate predict greater annual thermal amplitude in the study area, the limit between both communities could be displaced eastward

Exploiting Conceptual Modeling for Searching Genomic Metadata: A Quantitative and Qualitative Empirical Study

Providing a common data model for the metadata of several heterogenous genomic data sources is hard, as they do not share any standard or agreed practice for metadata description. Two years ago we managed to discover a subset of common metadata present in most sources and to organize it as a smart genomic conceptual model (GCM); the model has been instrumental to our efforts in the development of a major software pipeline for data integration. More recently, we developed a user-friendly search interface, based on a simplified version of GCM. In this paper, we report our evaluation of the effectiveness of this new user interface. Specifically, we present the results of a compendious empirical study to answer the research question: How much is such a simple interface well-understood by a standard user? The target of this study is a mixed population, composed by biologists, bioinformaticians and computer scientists. The result of our empirical study shows that the users were successful in producing search queries starting from their natural language description, as they did it with good accuracy and small error rate. The study also shows that most users were generally satisfied; it provides indications on how to improve our search system and how to continue our effort in integration of genomic sources. We are consequently adapting the user interface, that will be soon opened to public use

Surface characterization of Ti-Si-C-ON coatings for orthopedic devices : XPS and Raman spectroscopy

Ti–Si–C–ON films were deposited by DC reactive magnetron sputtering and their chemical properties, biofilm formation and toxicity were characterized. Based on the films composition three different growth regimes were identified on the films; (I) N/Ti = 2.11 (high atomic ratio) and low oxygen content; (II) 0.77 ≤ N/Ti ≤ 1.86 (intermediate atomic ratio) and (III) N/Ti ≤ 0.12 (low ratio) and high oxygen content. The phase composition varied from mainly TiN on regime I to TiCN on regime 2 and titanium oxides on regime III. Taking into account the results of biological characterization (biofilm formation and cytotoxicity), it was possible to conclude that samples with a high TiN content (regime I) presented more favorable biocompatibility, since it was less prone to microbial colonization and also displayed a low cytotoxicity.The authors are grateful to Dr. Alicia Andres, Institut de Ciencia de Materiales de Madrid (ICMM-CSIC), for his assistance in carrying out the Raman spectroscopic analysis. The work was financially supported by the CRUP Institution (project "Accao No E-1007/08), and the Spanish Ministry of Science and Innovation (projects FUN-COAT CSD2008-00023, MAT2008-06618-C02 and Integrated action HP016-2007). This research is partially sponsored by FEDER funds through the program COMPETE- Programa Operacional Factores de Competitividade and by Portuguese national funds through FCT-Fundacao para a Ciencia e a Tecnologia, under the project PTDC/CTM/102853/2008

Magnetic ordering of the antiferromagnet Cu2MnSnS4 from magnetization and neutron-scattering measurements

Magnetization and neutron-diffraction measurements were performed on a single crystal of Cu2MnSnS4. This quartenary magnetic semiconductor has the stannite structure (derived from the zinc-blende structure which is common to many II-VI dilute magnetic semiconductors), and it orders antiferromagnetically at low temperature. The neutron data for the nuclear structure confirm that the space group is I42̄m. Both the neutron and magnetization data give TN=8.8 K for the Néel temperature. The neutron data show a collinear antiferromagnetic (AF) structure with a propagation vector k=[1/2,0,1/2], in agreement with earlier neutron data on a powder. However, the deduced angle θ between the spin axis and the crystallographic c direction is between 6° and 16°, in contrast to the earlier value of 40°. The magnetization curve at T≪TN shows the presence of a spin rotation (analogous to a spin flop), which indicates that the spin axis is indeed close to the c direction. The deduced magnetic anisotropy gives an anisotropy field HA≅2 kOe. At high magnetic fields the magnetization curve at T≪TN shows the transition between the canted (spin-flop) phase and the paramagnetic phase. The transition field, H=245.5 kOe, yields an intersublattice exchange field HE= 124 kOe. The exchange constants deduced from HE and the Curie-Weiss temperature Θ=-25 K show that the antiferromagnetic interactions are an order of magnitude smaller than in II-VI dilute magnetic semiconductors (DMS's). The much weaker antiferromagnetic interactions are expected from the difference in the crystal structures (stannite versus zincblende). A more surprising result is that the exchange constant which controls the AF order below TN is not between Mn ions with the smallest separation. This result contrasts with a prediction made for the related II-VI DMS, according to which the exchange constants decrease rapidly with distance.The work at Tufts University was partially supported by NSF Grant No. DMR-9219727. The research in Zaragoza was supported by CICYT Grant No. MAT94-0043. The work at Brown University was supported by NSF Grant No. DMR-9221141. The Francis Bitter National Magnet Laboratory was supported by NSF.Peer Reviewe

Influence of the surface morphology and microstructure on the biological properties of Ti-Si-C-N-O coatings

Detailed structural, microstructural, biofilm formation and cytotoxicity studies were performed on Ti-Si-C-ON hard coatings prepared by dc reactive magnetron sputtering, in order to evaluate the relation among these properties. Compositional analysis showed the existence of two distinct regimens; regime I: high C/Si atomic ratio (C/Si ≥1,42) and intermediate N/Ti atomic ratio; regime II: low C/Si atomic ratio (C/Si≤0, 49) and low N/Ti atomic ratio. The structural analysis revealed that, in regime I, films crystallized in a B1-NaCl crystal structure typical of TiC0.2 N0.8. In regime II, the decrease of C/Si and increase in silicon concentration led to the formation of Ti-Si-CON along with a reduction of grain size in the films. Atomic Force Microscopy observations showed that the surface morphology of these Ti-Si-C-ON films became smoother when the silicon content increased and the nitrogen content decreased, which is consistent with the formation of nanosized clusters. Concerning biological properties, it was observed that cytotoxicity could be related with the titanium concentration while biofilm formation ability was found to be related with the surface morphology of the films.The authors are grateful to Dr. Alicia Andres, Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC), for her assistance in carrying out the Raman spectroscopic analysis. The project was financially supported by the CRUP Institution (project "Accao N0 E-1007/08"), and the Spanish Ministry of Science and Innovation (projects FUNCOAT CSD2008-00023 and HP2007-0116)

Longitudinal Analysis of Quality of Life, Clinical, Radiographic, Echocardiographic, and Laboratory Variables in Dogs with Preclinical Myxomatous Mitral Valve Disease Receiving Pimobendan or Placebo: The EPIC Study

Background: Changes in clinical variables associated with the administration of pimobendan to dogs with preclinical myxomatous mitral valve disease (MMVD) and cardiomegaly have not been described. Objectives: To investigate the effect of pimobendan on clinical variables and the relationship between a change in heart size and the time to congestive heart failure (CHF) or cardiac-related death (CRD) in dogs with MMVD and cardiomegaly. To determine whether pimobendan-treated dogs differ from dogs receiving placebo at onset of CHF. Animals: Three hundred and fifty-four dogs with MMVD and cardiomegaly. Materials and Methods: Prospective, blinded study with dogs randomized (ratio 1:1) to pimobendan (0.4-0.6 mg/kg/d) or placebo. Clinical, laboratory, and heart-size variables in both groups were measured and compared at different time points (day 35 and onset of CHF) and over the study duration. Relationships between short-term changes in echocardiographic variables and time to CHF or CRD were explored. Results: At day 35, heart size had reduced in the pimobendan group:median change in (Delta) LVIDDN -0.06 (IQR:-0.15 to + 0.02), P < 0.0001, and LA:Ao -0.08 (IQR:-0.23 to + 0.03), P < 0.0001. Reduction in heart size was associated with increased time to CHF or CRD. Hazard ratio for a 0.1 increase in Delta LVIDDN was 1.26, P = 0.0003. Hazard ratio for a 0.1 increase in Delta LA:Ao was 1.14, P = 0.0002. At onset of CHF, groups were similar. Conclusions and Clinical Importance: Pimobendan treatment reduces heart size. Reduced heart size is associated with improved outcome. At the onset of CHF, dogs treated with pimobendan were indistinguishable from those receiving placebo

Effect of Pimobendan in Dogs with Preclinical Myxomatous Mitral Valve Disease and Cardiomegaly: The EPIC Study - A Randomized Clinical Trial

Background: Pimobendan is effective in treatment of dogs with congestive heart failure (CHF) secondary to myxomatous mitral valve disease (MMVD). Its effect on dogs before the onset of CHF is unknown. Hypothesis/Objectives: Administration of pimobendan (0.4-0.6 mg/kg/d in divided doses) to dogs with increased heart size secondary to preclinical MMVD, not receiving other cardiovascular medications, will delay the onset of signs of CHF, cardiac-related death, or euthanasia. Animals: 360 client-owned dogs with MMVD with left atrial-to-aortic ratio >= 1.6, normalized left ventricular internal diameter in diastole >= 1.7, and vertebral heart sum >10.5. Methods: Prospective, randomized, placebo-controlled, blinded, multicenter clinical trial. Primary outcome variable was time to a composite of the onset of CHF, cardiac-related death, or euthanasia. Results: Median time to primary endpoint was 1228 days (95% CI: 856-NA) in the pimobendan group and 766 days (95% CI: 667-875) in the placebo group (P = .0038). Hazard ratio for the pimobendan group was 0.64 (95% CI: 0.47-0.87) compared with the placebo group. The benefit persisted after adjustment for other variables. Adverse events were not different between treatment groups. Dogs in the pimobendan group lived longer (median survival time was 1059 days (95% CI: 952-NA) in the pimobendan group and 902 days (95% CI: 747-1061) in the placebo group) (P = .012). Conclusions and Clinical Importance: Administration of pimobendan to dogs with MMVD and echocardiographic and radiographic evidence of cardiomegaly results in prolongation of preclinical period and is safe and well tolerated. Prolongation of preclinical period by approximately 15 months represents substantial clinical benefit