Imaging cytoplasmic cAMP in mouse brainstem neurons

Background  

cAMP is an ubiquitous second messenger mediating various neuronal functions, often as a consequence of increased intracellular Ca²⁺ levels. While imaging of calcium is commonly used in neuroscience applications, probing for cAMP levels has not yet been performed in living vertebrate neuronal tissue before.     

Complementary variational principles for radiation heat transfer in an absorbing medium

The radiation heat flux in a plane slab of an absorbing medium is evaluated by determining upper and lower bounds via complementary variational principles. The results obtained are in excellent agreement with those corresponding to other more cumbersome solution procedures (for small values of the spacing parameterd).

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Riassunto Si valuta il trasporto di energia raggiante in una lastra piana di un mezzo assorbente, determinandone limiti superiori ed inferiori, mediante principi variazionali complementari. I risultati ottenuti sono in eccellente accordo con quelli ottenuti mediante tecniche risolutive più complesse (per piccoli valori del parametrod).

     

Tubular-shaped stoichiometric chrysotile nanocrystals

Stoichiometric chrysotile tubular nanocrystals have been synthesized as possible starting materials for applications toward nanotechnology, and as a standard reference sample for the investigation of the molecular interactions between chrysotile, the most utilized asbestos, and biological systems. Chrysotile nanocrystals have been synthesized under controlled hydrothermal conditions, and have been characterized by chemical, morphological, structural, spectroscopic and microcalorimetric analyses. They show a constant "cylinder-in-cylinder" morphology constituted by two or three concentric subunits. Each single nanocrystal has a tubular shape of about 49+/-1 nm in outer maximum diameter, and a hollow core of about 7+/-1 nm. Structural investigation carried out on an X-ray powder pattern allowed to improve the structural model proposed for chrysotile mineral samples. Synthetic chrysotile crystallizes in the monoclinic Cc space group with a=0.5340(1) nm, b=0.9241(1) nm, and c=1.4689(2) nm, beta=93.66(3) degrees.     

Preparation and characterization of MgO stepped surfaces

We present a study of the preparation procedure for stepped MgO surfaces which can be used as templates for the deposition of metallic nanostructures. A cleaved sample of MgO(0 0 1) was mechanically polished to reach the desired miscut angle along the [1 1 0] direction. Then a thermal annealing was performed. The effect of an intermediate chemical etching has been also studied. The surface was analyzed by means of contact AFM in air, LEED and XPS in UHV. The role of the chemical etching and the dependence of the final morphology on the annealing time and temperature were investigated. The influence of the miscut angle on the final surface topography is also briefly discussed.     

Synthesis of Hexahydro‐2‐pyrindine (=Hexahydrocyclopenta[c]pyridine) Derivatives as Conformationally Restricted Analogs of the Nicotinic Ligands Arecolone and Isoarecolone

Two hexahydropyrindine derivatives, 1,2,3,4,6,7‐hexahydro‐2‐methyl‐5H‐cyclopenta[c]pyridin‐5‐one ( 1 ) and 1,2,3,4,5,6‐hexahydro‐2‐methyl‐7H‐cyclopenta[c]pyridin‐7‐one ( 2 ), and their methiodides 14 and 26 , respectively, were synthesized. They can be considered rigid analogues of the known nicotinic agonists arecolone (=1‐(1,2,5,6‐tetrahydro‐1‐methylpyridin‐3‐yl)ethanone) and isoarecolone (=1‐(1,2,3,6‐tetrahydro‐1‐methylpyridin‐4‐yl)ethanone). The affinity for the central nicotinic receptor were measured on rat cerebral cortex. Although only the methiodide 14 , among the four conformationally restricted compounds, shows an appreciable affinity, the results obtained provide useful information on the molecular requirements at the interaction site of the central nicotinic receptors.     

Statistics of particle pair relative velocity in the homogeneous shear flow

Small scale clustering of inertial particles and relative velocity of particle pairs have been fully characterized for statistically steady homogeneous isotropic flows. Depending on the particle Stokes relaxation time, the spatial distribution of the disperse phase results in a multi-scale manifold characterized by local particle concentration and voids and, because of finite inertia, the two nearby particles have high probability to exhibit large relative velocities. Both effects might explain the speed-up of particle collision rate in turbulent flows. Recently it has been shown that the large scale geometry of the flow plays a crucial role in organizing small scale particle clusters. For instance, a mean shear preferentially orients particle patterns. In this case, depending on the Stokes time, anisotropic clustering may occur even in the inertial range of scales where the turbulent fluctuations which drive the particles have already recovered isotropy. Here we consider the statistics of particle pair relative velocity in the homogeneous shear flow, the prototypical flow which manifests anisotropic clustering at small scales. We show that the mean shear, by imprinting anisotropy on the large scale velocity fluctuations, dramatically affects the particle relative velocity distribution even in the range of small scales where the anisotropic mechanisms of turbulent kinetic energy production are sub-dominant with respect to the inertial energy transfer which drives the carrier fluid velocity towards isotropy. We find that the particles’ populations which manifest strong anisotropy in their relative velocities are the same which exhibit small scale clustering. In contrast to any Kolmogorov-like picture of turbulent transport these phenomena may persist even below the smallest dissipative scales where the residual level of anisotropy may eventually blow-up. The observed anisotropy of particle relative velocity and spatial configuration is suggested to influence the directionality of the collision probability, as inferred on the basis of the so-called “ghost collision” model.     

Inertial Particles in Homogeneous Shear Turbulence: Experiments and Direct Numerical Simulation

The properties of the transport of heavy inertial particles in a uniformly sheared turbulent flow have been investigated by combining experimental and numerical data at particle Stokes number St?≈?0.3?÷?0.5 respectively. As in isotropic turbulence, particles are observed to avoid zones of intense enstrophy and to cluster in strain-dominated regions, resulting in highly intermittent spatial distributions. Moreover, the anisotropy of the mean flow is found to imprint a clear preferential orientation of the particle clusters in the direction of the maximum mean strain. These features are observed both in the numerics and in the experiments, and have been consistently quantified by a number of complementary statistical tools, such as the Voronoï tessellations and the pair correlation function. The latter quantity has been generalized in the form of the Angular Distribution Function and has allowed to evaluate the anisotropy content of the particle field at each scale. The behavior of this observable exhibits the same trend in the two datasets and suggests that, owing to increased inertia, the particle distribution starts to recover isotropy at scales smaller than the carrier velocity field. A proper rescaling of the two datasets in terms of their respective values of the shear scale allows to account for differences in the Reynolds number of experiments and numerics in the range of scales dominated by the mean shear.     

Morphology and spectral sensitivities of retinal and extraretinal photoreceptors in freshwater teleosts

Fish eyes possess a complicated morphological and neural organisation of retinal and extra-retinal receptors. Features such as photoreceptor mosaic array and photoreceptor grouping are unique among vertebrates. Spectral sensitivities of these photoreceptors range from UV to the red portion of the visible spectrum. Moreover, these sensitivities can change with the age of the animals. In this review we will examine thoroughly the morphology, and the spectral sensitivities of retinal and extra-retinal receptors and the influence upon them of factors such as hormones, ageing, season, habitat light conditions, and migration.     

An attractive way to recover information from ancient ceramics using EPR spectroscopy

Electron Paramagnetic Resonance (EPR) spectroscopy is useful to archeologists in recognizing and dating sites. This non-destructive technique of analysis gives information on material composition, on paramagnetic impurities, on firing techniques and on surface oxidation. In this paper it is shown how to recover information about firing techniques from a fragment of ceramic pot, dating from the 9th century B.C. The internal brown-black layer showed a strong g anisotropy whilst the external reddish layer showed hardly any. This indicates a non-homogeneous rapid firing of the pot, due probably to primitive firing techniques.