A Potent N-(piperidin-4-yl)-1H-pyrrole-2-carboxamide Inhibitor of Adenylyl Cyclase of G. lamblia: Biological Evaluation and Molecular Modelling Studies

In this work, we report a derivative of N-(piperidin-4-yl)-1H-pyrrole-2-carboxamide as a new inhibitor for adenylyl cyclase of Giardia lamblia which was obtained from a study using structural data of the nucleotidyl cyclase 1 (gNC1) of this parasite. For such a study, we developed a model for this specific enzyme by using homology techniques, which is the first model reported for gNC1 of G. lamblia. Our studies show that the new inhibitor has a competitive mechanism of action against this enzyme. 2-Hydroxyestradiol was used as the reference compound for comparative studies. Results in this work are important from two points of view. on the one hand, an experimentally corroborated model for gNC1 of G. lamblia obtained by molecular modelling is presented; on the other hand, the new inhibitor obtained is an undoubtedly excellent starting structure for the development of new metabolic inhibitors for G. lamblia.     

Entamoeba histolyticaelectrondense granules secretion in vitro and in vivo: ultrastructural study

Electron dense granules (EDGs) were identified by transmission electron microscopy in Entamoeba histolytica trophozoites recovered from hamster liver lesions. Abundant granules were present in trophozoites recovered after 15 min of liver inoculation. Variation in the size and morphology of these EDGs was also observed. Numerous granules were present in the plasma membrane when these parasites were incubated for 5 min with MDCK monolayers. Release of these EDGs was suggested by the presence of granules in contact with the surface of the target cell plasma membrane. Parasite phagocytic invaginations were observed after 10 min of parasite-monolayer interaction. In these structures, scarce granules were seen. Granules secretion was corroborated by obtaining of a pellet of these small structures from the incubation of trophozoites with collagen supernatant. Collagenase and gellatinase activity of this pellet was identified in SDS-PAGE gels. EDGs were also present in amebic hamster liver lesions. Our observations corroborate that these granules are secreted and suggest that may participate in the cytopathic effect of E. histolytica both in vitro and in vivo.     

Electrical transport mechanisms of Neodymium-doped rare-earth semiconductors

Journal of Materials Science: Materials in Electronics - This study reports the electrical properties of Nd-doped cerium oxide (CeO2) films synthesized by microwave assisted hydrothermal using a...     

Robust control under worst‐case uncertainty for unknown nonlinear systems using modified reinforcement learning

Reinforcement learning (RL) is an effective method for the design of robust controllers of unknown nonlinear systems. Normal RLs for robust control, such as actor‐critic (AC) algorithms, depend on the estimation accuracy. Uncertainty in the worst case requires a large state‐action space, this causes overestimation and computational problems. In this article, the RL method is modified with the k‐nearest neighbor and the double Q‐learning algorithm. The modified RL does not need the neural estimator as AC and can stabilize the unknown nonlinear system under the worst‐case uncertainty. The convergence property of the proposed RL method is analyzed. The simulations and the experimental results show that our modified RLs are much more robust compared with the classic controllers, such as the proportional‐integral‐derivative, the sliding mode, and the optimal linear quadratic regulator controllers.     

Legacy code and parallel computing: updating and parallelizing a numerical model

In this paper, we present several important details in the process of legacy code parallelization, mostly related to the problem of maintaining numerical output of a legacy code while obtaining a balanced workload for parallel processing. Since we maintained the non-uniform mesh imposed by the original finite element code, we have to develop a specially designed data distribution among processors so that data restrictions are met in the finite element method. In particular, we introduce a data distribution method that is initially used in shared memory parallel processing and obtain better performance than the previous parallel program version. Besides, this method can be extended to other parallel platforms such as distributed memory parallel computers. We present results including several problems related to performance profiling on different (development and production) parallel platforms. The use of new and old parallel computing architectures leads to different behavior of the same code, which in all cases provides better performance in multiprocessor hardware.

     

Stabilization of Telomeric I‐Motif Structures by (2′S)‐2′‐Deoxy‐2′‐C‐Methylcytidine Residues

G‐quadruplexes and i‐motifs are tetraplex structures present in telomeres and the promoter regions of oncogenes. The possibility of producing nanodevices with pH‐sensitive functions has triggered interest in modified oligonucleotides with improved structural properties. We synthesized C‐rich oligonucleotides carrying conformationally restricted (2′S)‐2′‐deoxy‐2′‐C‐methyl‐cytidine units. The effect of this modified nucleoside on the stability of intramolecular i‐motifs from the vertebrate telomere was investigated by UV, CD, and NMR spectroscopy. The replacement of selected positions of the C‐core with C‐modified residues induced the formation of stable intercalated tetraplexes at near‐neutral pH. This study demonstrates the possibility of enhancing the stability of the i‐motif by chemical modification.     

Embedded spectroscopic fiber sensor for on-line arc-welding analysis

A new fiber sensor system designed for spectroscopic analysis and on-line quality assurance of arc-welding processes is presented here. Although several different approaches have been considered for the optical capture of plasma emission in arc-welding processes, they tend to be invasive and make use of optical devices such as collimators or photodiodes. The solution proposed here is based on the arrangement of an optical fiber, which is used at the same time as the optical capturing device and also to deliver the optical information to a spectrometer, embedded within an arc-welding torch. It will be demonstrated that, by using the shielding gas as a protection for the fiber end, the plasma light emission is efficiently collected, forming a sensor system completely transparent and noninvasive for the welding operator. The feasibility of the proposed sensor designed to be used as the input optics of a welding quality-assurance system based on plasma spectroscopy will be demonstrated by means of several welding tests.     

Effect of Ba and rare earths cations on the properties and dehydrocyclization activity of Pt/K‐LTL catalysts

Several Pt/L‐zeolite catalysts were prepared by the impregnation method from L‐zeolite samples previously exchanged with Ba²⁺, La³⁺, Pr³⁺, Nd³⁺ and Sm³⁺. Lanthanides (Ln³⁺) increase the overall dispersion of platinum, measured by H₂–O₂ titration. TPR and CO/FTIR measurements indicate that these ions modify the distribution of Pt in the zeolite lattice, increasing the fraction of metal on the external surface. Additionally, both CO/FTIR and competitive hydrogenation of toluene–benzene mixtures indicate that, in the presence of Ln³⁺, the electron density of the platinum decreases in comparison with Pt/KL‐zeolite. On the other hand, Ba²⁺ does not substantially modify neither the distribution nor the electronic state of Pt. The reactivity measurements in the hydroconversion of n‐heptane show that Pt/BaKL and Pt/KL exhibit similar catalytic behaviour with a high dehydrocyclization activity. However, the exchange of K⁺ by Ln³⁺ increases the production of heptane isomers, while selectivities to aromatic and terminal hydrogenolysis products significantly decrease. This revised version was published online in July 2006 with corrections to the Cover Date.