Atomic structure and segregation in alkali-metal heteroclusters

The ground-state atomic and electronic distributions in NamCsn clusters with composition m=n and m=2n have been calculated by minimizing the total cluster energy using the density-functional formalism. The approximation is made by replacing the total external potential of the ions by its spherical average around the cluster center during the iterative process of solving the Kohn-Sham equations for each geometry tested. In the size range studied here (up to 90 atoms per cluster), the cluster is composed of well-separated homoatomic Na and Cs shells, the external one always being a Cs shell. We have also found that the cohesive energy goes rapidly to the bulk limit. An analysis of the geometries shows strong cluster reconstruction with increasing size. By comparing the geometry of pure Nan with that of the Nan core in NanCsn for clusters formed by only an inner Na layer and an outer Cs layer, we have observed that the Nan core adopts a geometry different in most cases from that of the free Nan cluster, and such that the number of faces of the polyhedron formed by the Nan core is as close as possible to the number of external Cs atoms, in order to accomodate these Cs atoms on top of the faces of the polyhedron

Organocatalytic asymmetric domino Michael–Henry reaction for the synthesis of substituted bicyclo[3.2.1]octan-2-ones

This paper was submitted for publication in the journal "Chemical Communications" and the definitive version can be found at: http://dx.doi.org/10.1039/c3cc39165eThe first organocatalytic asymmetric reaction between 1,4-cyclohexanedione and nitroalkenes have been studied, affording bicyclo[3.2.1]octane derivatives containing four continuous stereogenic centres. The products were obtained through a domino Michael-Henry process as a single diastereoisomer with excellent enantioselectivities

Prolinethioamides versus Prolinamides in Organocatalyzed Aldol Reactions—A Comparative Study

Various organocatalysts have been developed for the aldol reaction but particular attention has been paid to prolinamide derivatives. They are easy to prepare and their catalytic activity can be readily tuned through structural modification. In this review, the comparison of catalytic activities between prolinethioamides and their respective amides in direct asymmetric aldol reactions is presented

Characterization of multi-emitter tuneable led source for endoscopic applications

In this paper we describe our own construction of a tuneable light source based on a set of light emitting diodes covering the visible spectrum using a homogenizing rod instead commonly used low energy-efficient integrating spheres. The expected prime application of the source is a medical endoscopic system, however it is possible to use it also for other purposes requiring both multispectral operation and a tuneable white light source. We describe the construction of the source and include precise characterization of the output white light - distribution of CCT, Duv, ∆u’v’ and colour rendering indexes (Ra, R9, Rf, Rg) of light in several planes located at various distances. The obtained results prove that our source is characterized by very good colour rendition according to the Ra and Rf method for various correlated colour temperatures (2700-6500) K. As an example of application images of the Macbeth colour chart registered with an RGB camera included in the laboratory measurement stand are presented. The obtained results prove that, after whole system calibration, this source can be used in many applications, where evaluation of objects requires precise analysis of their colour and multispectral procedures

Research on substances with activity against orthopoxviruses

Although smallpox was eradicated over 30 years ago, the disease remains a major threat. High mortality, high infectivity and low resistance of the contemporary population make the smallpox virus very attractive to terrorists. The possible presence of illegal stocks of the virus or risk of deliberate genetic modifications cause serious concerns among experts. Hence, it is reasonable to seek effective drugs that could be used in case of smallpox outbreak. This paper reviews studies on compounds with proven in vitro or in vivo antipoxviruses potential, which show various mechanisms of action. Nucleoside analogues, such as cidofovir, can inhibit virus replication. Cidofovir derivatives are developed to improve the bioavailability of the drug. Among the nucleoside analogues under current investigation are: ANO (adenozine N1-oxide) and its derivatives, N-methanocarbothymidine [(N)-MCT], or derivatitives of aciklovir, peninclovir and brivudin. Recently, ST-246 – which effectively inhibits infection by limiting release of progeny virions – has become an object of attention. It has been also been demonstrated that compounds such as: nigericin, aptamers and peptides may have antiviral potential. An interesting strategy to fight infections was presented in experiments aimed at defining the role of individual genes (E3L, K3L or C6L) in the pathogenesis, and looking for their potential blockers. Additionally, among substances considered to be effective in the treatment of smallpox cases, there are factors that can block viral inhibitors of the human complement system, epidermal growth factor inhibitors or immunomodulators. Further studies on compounds with activity against poxviruses are necessary in order to broaden the pool of available means that could be used in the case of a new outbreak of smallpox