Out of equilibrium anomalous elastic response of a water nano-meniscus

We report the observation of a transition in the dynamical properties of water nano-menicus which dramatically change when probed at different time scales. Using a AFM mode that we name Force Feedback Microscopy, we observe this change in the simultaneous measurements, at different frequencies, of the stiffness G'(N/m), the dissipative coefficient G''(kg/sec) together with the static force. At low frequency we observe a negative stiffness as expected for capillary forces. As the measuring time approaches the microsecond, the dynamic response exhibits a transition toward a very large positive stiffness. When evaporation and condensation gradually lose efficiency, the contact line progressively becomes immobile. This transition is essentially controlled by variations of Laplace pressure

Experimental study of the binding energy of NH3 on different types of ice and its impact on the snow line of NH3 and H2O

N-bearing molecules (like N2H+ or NH3) are excellent tracers of high-density, low-temperature regions like dense cloud cores and could shed light into snowlines in protoplanetary disks and the chemical evolution of comets. However, uncertainties exist about the grain surface chemistry of these molecules -- which could play an important role in their formation and evolution. This study explores experimentally the behaviour of NH$_3$ on surfaces mimicking grains under interstellar conditions alongside other major interstellar ice components (ie. H$_2$O, CO, CO$_2$). We performed co-deposition experiments using the Ultra High Vacuum (UHV) setup VENUS (VErs des NoUvelles Syntheses) of NH$_3$ along with other adsorbates (here, H$_2$O, $^{13}$CO and CO$_2$) and performed Temperature Programmed Desorption (TPD) and Temperature Programmed-During Exposure Desorption (TP-DED) experiments. We obtained binding Energy (BE) distribution of NH$_3$ on Crystalline Ice(CI) and compact-Amorphous Solid Water (c-ASW) by analyses of the TPD profiles of NH3 on the substrates. We observe a significant delay in the desorption and a decrease in the desorption rate of NH$_3$ when H$_2$O is introduced into the co-deposited mixture of NH$_3$-$^{13}$Co or NH$_3$-CO$_2$, absent without H$_2$O. Secondly, H$_2$O traps nearly 5-9 per cent of the co-deposited NH3, released during water's amorphous-to-crystalline phase change. Thirdly, for CI, we obtained a BE distribution between 3780K-4080K, and c-ASW between 3780K-5280K -- using a pre-exponential factor A = 1.94$\times 10^{15}$/s. We conclude that NH$_3$ behaviour is significantly influenced by the presence of H$_2$O due to the formation of hydrogen bonds, in line with quantum calculations. This interaction preserves NH$_3$ on grain surfaces to higher temperatures making it available to the central protostar in protoplanetary disks. It also explains why NH$_3$ freeze out in pre-stellar cores is efficient

Innovativeness and network competence : an integration and empirical examination

This paper reports a study of the interdependence of network competence and innovativeness in a product innovation context. Based on a systematic review on innovation literature, authors define two review constructs for innovativeness and network competence. The dimensions of both concepts were validated through a sample of 164 manufacturing Portuguese firms, which provides interesting results concerning the behavior of Portuguese manufacturing companies at the level of network innovation

The dimensions of purchasing competence: a synthesis from literature

Organizational buying behavior has been dramatically changing due to transformations on the nature of industrial competition. This changing environment implies great demands to companies to remain competitive. As firms recognize the purchasing function as an important resource for obtaining high quality levels, fast deliveries and cost savings, it reveals opportunities for the purchasing management to become a business key contributor. This paper presents a critical literature review concerning the new strategic role for purchasing. We develop a construct of purchasing competence using three dimensions identified from literature: purchasing interaction, purchasing importance, and purchasing task execution

The dimensions of purchasing competence

As firms recognize the purchasing function as an important resource for obtaining high quality levels, fast deliveries and cost savings, it reveals opportunities for the purchasing management to become a key contributor. The new product development is one example where acquisition capabilities may confirm to be particularly critical. This paper presents a construct of purchasing competence using three dimensions identified from literature: purchasing interaction, purchasing importance, and purchasing task execution. We discuss the dimensions based on a critical literature review concerning the new strategic role for purchasing. The dimensions of our purchasing competence construct were validated through a sample of 164 manufacturing Portuguese firms

“Sobre o rumo da literatura de revista nos anos de 1834 e 1835”: tradução do polêmico artigo de N. V. Gógol na revista “O Contemporâneo”, de A. S. Púchkin

Em 1836, a revista “O Contemporâneo”, de A. S. Púchkin, publica um ácido e extremamente crítico artigo apócrifo. Creditado tardiamente a Nikolai Vassílievitch Gógol, “Sobre o rumo da literatura de revista nos anos de 1834 e 1835” apresenta o cenário da crítica literária da época. Neste artigo, a primeira parte do longo texto é apresentada em tradução direta do original, em russo

Variation of Burkholderia cenocepacia cell wall morphology and mechanical properties during cystic fibrosis lung infection, assessed by atomic force microscopy

The influence that Burkholderia cenocepacia adaptive evolution during long-term infection in cystic fibrosis (CF) patients has on cell wall morphology and mechanical properties is poorly understood despite their crucial role in cell physiology, persistent infection and pathogenesis. Cell wall morphology and physical properties of three B. cenocepacia isolates collected from a CF patient over a period of 3.5 years were compared using atomic force microscopy (AFM). These serial clonal variants include the first isolate retrieved from the patient and two late isolates obtained after three years of infection and before the patient's death with cepacia syndrome. A consistent and progressive decrease of cell height and a cell shape evolution during infection, from the typical rods to morphology closer to cocci, were observed. The images of cells grown in biofilms showed an identical cell size reduction pattern. Additionally, the apparent elasticity modulus significantly decreases from the early isolate to the last clonal variant retrieved from the patient but the intermediary highly antibiotic resistant clonal isolate showed the highest elasticity values. Concerning the adhesion of bacteria surface to the AFM tip, the first isolate was found to adhere better than the late isolates whose lipopolysaccharide (LPS) structure loss the O-antigen (OAg) during CF infection. The OAg is known to influence Gram-negative bacteria adhesion and be an important factor in B. cenocepacia adaptation to chronic infection. Results reinforce the concept of the occurrence of phenotypic heterogeneity and adaptive evolution, also at the level of cell size, form, envelope topography and physical properties during long-term infection

DNA metabarcoding unveils niche overlapping and competition among Caribbean sea urchins

Detailed information of trophic interactions among consumer-resources in food webs is usually limited due to the lack of accurate identification of eaten food resources. The use of DNA-metabarcoding has been proven useful for molecular identification of the numerous taxa present in stomach contents. Here, we characterize the diet and trophic behavior of four sea urchin species inhabiting shallow waters of Puerto Rico using this molecular technique. We extracted, sequenced, and analyzed DNA from the gut content of a total of 60 individuals collected at three sites at the northeastern coast of Puerto Rico. Our results demonstrated that seaweeds were the dominant food source for the four sea urchin species at all three sites, but also small protists, fungi and metazoans were important components of sea urchin's diet. Interspecific differences in diet were also found among sites. PERMANOVA analysis detected significant differences among species (Pseudo-F 1.755, p < 0.001), and among sites (Pseudo-F 2.52, p < 0.001). A SIMPER analysis showed that in all cases the main taxa causing differences between species and sites were macroalgae (Rhodophyta, Chlorophyta and Ochrophyta) with some contribution of small eukaryotes (Apicomplexa and Bacillariophyta). This diet characterization in sea urchins revealed a generalist omnivore behavior, but with a clear dominance of algae as a main dietary component. Thus, we found a potential inter-specific competition due to niche overlapping, which seems to be more common than initially thought

Avaliação da maturação em azeitona ‘Cobrançosa’ e ‘Galega Vulgar’ com recurso a diferentes metodologias baseadas na cor dos frutos

No presente trabalho estudaram-se três métodos de avaliação do estado de Maturação da azeitona, baseados na coloração dos frutos das cultivares ‘Cobrançosa’ e ‘Galega Vulgar’ em estados precoces de maturação, bem como a sua relação com a acumulação de gordura. Os métodos estudados foram: IM – índice de maturação de Jaén (com 8 grupos de cor); IMS – índice de maturação simplificado com apenas três classes de cor; CI – índice de cor (Colour Index) utilizando o Sistema CIE de cor L*a*b*. Os resultados obtidos revelaram que os índices de maturação baseados na cor dos frutos são úteis para caracterizar a evolução do teor em gordura durante a maturação da azeitona. O método simplificado apresentou uma elevada correlação com o índice de Jaén, sendo bastante mais rápido e de mais fácil utilização pelo olivicultor