Search results for " recognition"
showing 10 items of 3220 documents
Polyfunctional recognition of pyridinedicarboxylate anions with macrocyclic polyamine receptors containing heteroaromatic groups.
2008
The interaction of the biologically relevant anions deriving from the six pyridinedicarboxylic acids (H2PDC) with two macrocyclic receptors containing a pentamine chain and a bipyridine (1) or a phenanthroline (2) moiety, as well as with the aliphatic analogue [21]aneN7 (3), was studied by means of spectroscopic methods (UV-vis, NMR) and potentiometric titrations affording the stability constants of the adducts formed. All three receptors form stable complexes with the substrates thanks to the formation of several salt bridges and hydrogen bond contacts, as observed in the crystal structure of the H8[3(2,6-PDC)4] x H2O x 0.5 EtOH solid compound. Additional pi-stacking interactions between t…
A highly enantioselective abiotic receptor for malate dianion in aqueous solution
2006
The highly enantioselective molecular recognition of the malate dianion by a synthetic receptor in aqueous solution has been studied by potentiometric titrations, mass spectrometry (ESI-MS), diffusion measurements (PGSE NMR) and molecular modeling. Garcia-España Monsonis, Enrique, Enrique.Garcia-Es@uv.es
[3.3]Ferrocenophanes with guanidine bridging units as multisignalling receptor molecules for selective recognition of anions, cations, and amino acid…
2007
The synthesis, electrochemical, and optical properties of a new [3.3]ferrocenophane framework in which two ferrocene subunits, with similar electronic environments, are linked through two substituted guanidine moieties, are reported. The receptors 4-7 have been prepared in good yields by the reaction of bis(carbodiimide) 3 with primary amines. This architecture is exceptionally "tunable" because a variety of "legs" may be appended to the basic [3.3]ferrocenophane scaffold to give a wide range of signaling units. These receptors show remarkable ion-sensing properties, due to the presence of a redox active unit (ferrocene), and an amphoteric binding site (guanidine). In this nitrogen-rich str…
Anion Recognition by a Bioactive Diureidodecalin Anionophore: Solid-State, Solution, and Computational Studies
2018
Recent work has identified a bis-(p-nitrophenyl)ureidodecalin anion carrier as a promising candidate for biomedical applications, showing good activity for chloride transport in cells yet almost no cytotoxicity. To underpin further development of this and related compounds, a detailed structural and binding investigation is reported. Crystal structures of the transporter as five solvates confirm the diaxial positioning of urea groups while revealing a degree of conformational flexibility. Structures of complexes with Cl−, Br−, NO3 −, SO4 2− and AcO−, supported by computational studies, show how the binding site can adapt to accommodate these anions. 1H NMR binding studies revealed exception…
Ion-Pairing Effects in the Self-Assembly of a Fluorescent Pseudorotaxane
2006
Herein we report on the self-assembly, in a low polarity solvent, of a pseudorotaxane species comprising binaphthyl-26-crown-8 (BN26C8) as the macrocyclic host and anthracenyl-benzylammonium as the threadlike positively charged guest (ABH+). Absorption and luminescence data reveal a very efficient energy transfer process occurring from the binaphthyl to the anthracene singlet excited states. The self-assembly is highly dependent on the nature of the counteranion confirming the crucial role played by it in the competition between the self-assembly process and the formation of ion pairs (ABH+X-). This behavior can be readily evidenced in dilute solutions from the analysis of the luminescence …
The cryogenic anticoincidence detector for ATHENA-XMS: preliminary results from the new prototype
2012
ATHENA has been the re-scoped IXO mission, and one of the foreseen focal plane instrument was the X-ray Microcalorimeter Spectrometer (XMS) working in the energy range 0.3-10 keV, which was a kilo-pixel array based on TES (Transition Edge Sensor) detectors. The need of an anticoincidence (AC) detector is legitimated by the results performed with GEANT4 simulations about the impact of the non x-ray background onto XMS at L2 orbit (REQ. < 0.02 cts/cm2/s/keV). Our consortium has both developed and tested several samples, with increasing area, in order to match the large area of the XMS (64 mm2). Here we show the preliminary results from the last prototype. The results achieved in this work off…
The importance of pattern similarity between Müllerian mimics in predator avoidance learning
2004
Müllerian mimicry, where unpalatable prey share common warning patterns, has long fascinated evolutionary biologists. It is commonly assumed that Müllerian mimics benefit by sharing the costs of predator education, thus reducing per capita mortality, although there has been no direct test of this assumption. Here, we specifically measure the selection pressure exerted by avian predators on unpalatable prey with different degrees of visual similarity in their warning patterns. Using wild-caught birds foraging on novel patterned prey in the laboratory, we unexpectedly found that pattern similarity did not increase the speed of avoidance learning, and even dissimilar mimics shared the educatio…
Comparison and multiresolution analysis of irregular meshes with appearance attributes
2004
We present in this dissertation a method to compare and to analyse irregular meshes with appearance attributes. First, we propose a mesh comparison method using a new attribute deviation metric. Considered meshes contain geometric and appearance attributes (e.g. color, texture,temperature). The proposed deviation assessment allows the computation of local attribute differences between two meshes. We present an application of this method to mesh simplification algorithm quality assessment.Then we propose two multiresolution analysis schemes for irregular meshes with appearance attributes. First, a mesh is decomposed in a discret number of levels of detail. We introduce a surface geometry rel…
A Hardware and Secure Pseudorandom Generator for Constrained Devices
2018
Hardware security for an Internet of Things or cyber physical system drives the need for ubiquitous cryptography to different sensing infrastructures in these fields. In particular, generating strong cryptographic keys on such resource-constrained device depends on a lightweight and cryptographically secure random number generator. In this research work, we have introduced a new hardware chaos-based pseudorandom number generator, which is mainly based on the deletion of an Hamilton cycle within the $N$ -cube (or on the vectorial negation), plus one single permutation. We have rigorously proven the chaotic behavior and cryptographically secure property of the whole proposal: the mid-term eff…
Localisation visuelle basée sur la reconnaissance du lieu dans les environnements changeants
2017
In many applications, it is crucial that a robot or vehicle localizes itself within the world especially for autonomous navigation and driving. The goal of this thesis is to improve place recognition performance for visual localization in changing environment. The approach is as follows: in off-line phase, geo-referenced images of each location are acquired, features are extracted and saved. While in the on-line phase, the vehicle localizes itself by identifying a previously-visited location through image or sequence retrieving. However, visual localization is challenging due to drastic appearance and illumination changes caused by weather conditions or seasonal changing. This thesis addres…