Search results for "chemical science"
showing 10 items of 9771 documents
Cadmium Metal–Organic Frameworks Based on Ditopic Triazamacrocyclic Linkers: Unusual Structural Features and Selective CO 2 Capture
2017
International audience; Two three-dimensional cadmium metal organic frameworks with general formula [Cd-2(L-1)(H2O)(3)](NO3)(0.7)(HCOO)(0.2)Br-0.1 (Cd2L1, L-1 = 1,4,7-tris(4-carboxybenzy1)-1,4,7-triazacyclononane) and Cd(HL2)(H2O)(2) (CdL2, L-2 = 1,4,7-tris(3-(4-benzoate)prop-2-yn-1-yl)-1,4,7-triazacydononane) based on 1,4,7-triazacyclononane N-functionalized by different arylcarboxylic acids were prepared under solvothermal conditions and characterized by single crystal X-ray analysis and porosity measurements. The crystal structure of Cd2L1 reveals a cationic net with a bcs topology,. and nodes are constituted by dinuclear cadmium complexes, in which each cadmium atom adopts a hexacoordin…
Biodegradable Metal-Organic Framework-Based Microrobots (MOFBOTs).
2020
Microrobots and metal–organic frameworks (MOFs) have been identified as promising carriers for drug delivery applications. While clinical applications of microrobots are limited by their low drug loading efficiencies and the poor degradability of the materials used for their fabrication, MOFs lack motility and targeted drug delivery capabilities. The combination of these two fields marks the beginning of a new era; MOF‐based small‐scale robots (MOFBOTs) for biomedical applications. Yet, biodegradability is a major hurdle in the field of micro‐ and nanoswimmers including small‐scale robots. Here, a highly integrated MOFBOT that is able to realize magnetic locomotion, drug delivery, and selec…
Statistical Approximation of Fourier Transform-IR Spectroscopy Data for Zinc White Pigment from Twentieth-Century Russian Paintings
2017
We present a statistical model for approximation of experimental Fourier transform-IR spectroscopy (FTIR) data for paint samples from paintings of different ages. The model utilizes random variations in some parameters (initial ageing rate, degree of change in ageing rate and time at which the change occurs). We determine the parameters characterizing variation in the paint composition and the storage conditions for the paintings. The numerical calculation is qualitatively consistent with the experimental data. In the proposed model, changes in the initial composition of the paint and the storage conditions make about the same contribution to the experimentally observed scatter in the data …
Développement et caractérisation d’électrodes pour l’électrolyse alcaline de l’eau
2020
Splitting water into hydrogen and oxygen by electrolysis using electricity from intermittent ocean current, wind, or solar energies is one of the easiest and cleanest routes for high-purity hydrogen production and an effective way to store the excess electrical power without leaving any carbon footprints. The key dilemma for efficient large-scale production of hydrogen by splitting of water via the hydrogen and oxygen evolution reactions is the high overpotential required, especially for the oxygen evolution reaction. Hence, engineering highly active and stable earth-abundant oxygen evolution electrocatalysts with three-dimensional hierarchical porous architecture via facile, effective and …
Chemical Composition of the Essential Oil of Bupleurum Fontanesii (Apiaceae) Growing Wild in Sicily and its Activity on Microorganisms Affecting Hist…
2016
Hydrodistillation of the flowers (BpFl) of and fruits (BpFr) of Bupleurum fontanesii Guss. ex Caruel gave two oils that were analyzed by GC and GC-MS. The main components were α-elemol (16.7%), caryophyllene oxide (16.4%) and heptacosane (15.9%) in BpFl, and spathulenol (16.8%), caryophylladienol I (13.2%) and α-elemol (12.8%) in BpFr. A good antimicrobial activity against several microorganisms, including Bacillus subtilis, Staphylococcus aureus, Fusarium oxysporum and Aspergillus niger, all infesting historical art craft, was also determined.
Chemical composition and biological activity of the essential oil of Ballota hispanica (L.) Benth. growing wild in Sicily
2015
Ballota L. comprises several relevant species largely used for their excellent therapeutic properties. Ballota hispanica (L.) Benth. is widely used in herbal medicine, and it is sold in herbalist shops for its sedative and antispasmodic properties. Considering its traditional medicinal use and the lack of scientific studies on the volatile components of this species as well as on its biological activities, in this study the chemical composition of the essential oil from aerial parts of B. hispanica, collected in Sicily, was evaluated by gas chromatography and gas chromatographyâmass spectrometry. α-Elemol was the most abundant component of the oil (10.9%), followed by α-ylangene (8.5%),…
Contribution to the modeling of microstructural corrosion on aluminium alloys : definition of a methodology to study the bimetallic corrosion phenome…
2008
The initiation and the propagation of aluminum alloys microstructural corrosion is mainly based on the bimetallic corrosion phenomenon. This type of corrosion is caused by galvanic coupling at a local scale between the different phases contained in the alloy. The description of the localized corrosion phenomenon has been largely studied. Their complexity can explain why they are so difficult to predict by the way of numerical tools and why the works that have been done on this subject are so scarce. The present thesis brings a new contribution to this field by suggesting a methodology based on the complementary use of local electrochemical techniques and the finite element simulation of bim…
Photoluminescence properties of S2 molecule trapped in Melanophlogite
2015
We studied the photoluminescence properties of a sample of SiO2-clathrate Melanophlogite, a crystalline microporous material which is found in nature as a rare mineral. Upon β irradiation, the material displays an intense light emission under near-UV illumination. We studied in detail this optical activity by steady-state and time-resolved photoluminescence measurements as a function of temperature. The spectroscopic properties we find can be ascribed to a population of quasi-free molecules trapped within each of the two different types of cage available in the structure of this clathrate, although the spectroscopic properties of the guest molecules are affected by their interactions with t…
Desymmetrization of Prochiral Cyclobutanones via Nitrogen Insertion: A Concise Route to Chiral γ‐Lactams
2021
Abstract Asymmetric access to γ‐lactams is achieved via a cyclobutanone ring expansion using widely available (1S,2R)‐1‐amino‐2‐indanol for chiral induction. Mechanistic analysis of the key N,O‐ketal rearrangement reveals a Curtin–Hammett scenario, which enables a downstream stereoinduction (up to 88:12 dr) and is corroborated by spectroscopic, crystallographic, and computational studies. In combination with an easy deprotection protocol, this operationally simple sequence allows the synthesis of a range of optically pure γ‐lactams, including those bearing all‐carbon quaternary stereocenters. In addition, the formal synthesis of drug molecules baclofen, brivaracetam, and pregabalin further …
The Use of Stable Isotope Ratio Analysis to Trace European Sea Bass (D. labrax) Originating from Different Farming Systems
2020
This study aimed to determine whether isotopic ratio mass spectrometry (IRMS) can discriminate farmed European sea bass according to different farming systems and geographic origins. Dicentrarchus labrax of commercial size from three different rearing systems (concrete tank inland, sea cages, and extensive methods in valleys or salt works) were collected at the trading period (autumn&ndash