Search results for " Supported"

An approach to polymer-supported triplet benzophenone photocatalysts. Application to sustainable photocatalysis of an α-diazocarbonyl compound

2013

Covalent immobilization of 4-hydroxybenzophenone on Merrifield resins affords new heterogeneous polymeric triplet photocatalysts. Their successful application in the intramolecular triplet-sensitized photolysis of a α-diazo β-keto ester has been achieved under sustainable criteria. Remarkably, the simple recovery and reuse for up to five sequential applications have been performed, although resulting in a slightly decreasing activity.

Transform Farming With the Help of Social Media A Pioneering Chinese Community Supported Agriculture (CSA) Farm and Its Micro Blog USA

2016

Cross-Device Augmented Reality Annotations Method for Asynchronous Collaboration in Unprepared Environments

2021

Augmented Reality (AR) annotations are a powerful way of communication when collaborators cannot be present at the same time in a given environment. However, this situation presents several challenges, for example: how to record the AR annotations for later consumption, how to align virtual and real world in unprepared environments or how to offer the annotations to users with different AR devices. In this paper we present a cross-device AR annotation method that allows users to create and display annotations asynchronously in environments without the need for prior preparation (AR markers, point cloud capture, etc.). This is achieved through an easy user-assisted calibration process and a …

Synthesis and characterization of ethylene-1-hexene copolymers prepared by using MgCl2(THF)2-supported Ziegler-Natta catalysts

2000

Ethylene was copolymerized with 1-hexene over vanadium (VOCl3 and VCl4) and titanium (TiCl4) catalysts supported on MgCl2(THF)2 and activated with Et2AlCl. So far these catalyst systems have not been known as initiators of ethylene-1-hexene copolymerization. The vanadium catalysts were more active than the titanium catalyst and, at identical comonomer concentrations in the feed, gave rise to a greater incorporation of 1-hexene into the copolymer. Even at relatively low fractions of 1-hexene, the MgCl2(THF)2-supported catalysts affected much the copolymer properties like density, melting point and crystallinity.

Determination of Glyphosate and AMPA in Food Samples Using Membrane Extraction Technique for Analytes Preconcentration

2021

The method for determining glyphosate (NPG) and its metabolite AMPA (aminomethyl phosphonic acid) in solid food samples using UAE-SLM-HPLC–PDA technique was developed. Firstly, ultrasonic-assisted solvent extraction (UAE) and protein precipitation step were used for the analyte isolation. Then, the supernatant was evaporated to dryness and redissolved in distilled water (100 mL). The obtained solution was alkalized to pH 11 (with 1 M NaOH) and used directly as donor phase in SLM (supported liquid membrane) extraction. The SLM extraction was performed using 2 M NaCl (5 mL) as an acceptor phase. The flow rate of both phases (donor and acceptor) was set at 0.2 mL/min. The membrane extraction t…

GREEN CONDITIONS FOR THE SUZUKI REACTIONS BY USING MICROWAVE IRRADIATION AND MODIFIED HALLOYSITE/Pd CATALYST

2014

Halloysite nanotube (HNT) is an emerging biocompatible material with appealing perspective for technological applications, such as in catalysis1 and in pharmaceutical research.2 Halloysite is a double-layered aluminosilicate mineral that has a predominantly hollow tubular structure. The functionalization of HNTs is a good strategy to introduce an organic moiety onto the external surface and, therefore, to obtain innovative catalyst supports.3 We have modified the external surface of halloysite nanotube with octylimidazolium moieties (HNT-IL) by microwave irradiation in solvent-free conditions and we have have employed this material as support catalyst of Pd nanoparticles. The new HNT/Pd cat…

SYNTHESIS AND EVALUATION OF CATALYTIC ACTIVITY IN WATER AND MICROWAVE IRRADIATION OF A NEW SUPPORT BASED ON HNT TRIAZOLIUM SALTS

2014

In the last years SILLP (supported ionic liquid-like phase)-based materials prepared by covalent attachment have been synthesized [1]. Recently, we have synthesized a palladium-based catalytic system using halloysite nanotubes modified with octylimidazolium moieties and we have tested it in the Suzuki cross-coupling reaction under traditional heating, microwave irradiation and a very small amount of Pd catalyst [2,3]. It is known that support based on triazole motif showed superior activity to the analogous imidazole molecules [4] so, we have focused our attention to develop a new SILLP system with triazolium moiety. Herein we report the synthesis of an original Pd-dicationic triazolium sup…

Cross-Linked Imidazolium Salts as Scavengers for Palladium.

2014

Five imidazolium-based materials have been synthesised and used for the first time as palladium scavengers. Radical reactions of suitable bis-vinylimidazolium salts led to a series of insoluble materials through homo-polymerisation, immobilisation with a 3-mercaptopropyl-modified silica gel or co-polymerisation with ethylene glycol dimethylacrylate. These materials were screened as palladium scavengers with a set of palladium(0) and palladium(II) compounds in different solvents and at different starting amounts of palladium. In many cases, residual amounts of palladium were lower than 5 ppm, as requested for the manufacture of active pharmaceutical ingredients and fine chemicals. The applic…

Dual stereocontrolled alkylation of aldehydes with polystyrene-supported nickel complexes derived from α-amino amides

2015

Nickel(II) complexes derived from α-amino amide ligands anchored to gel-type and monolithic polymers act as efficient catalysts for the enantioselective addition of dialkylzinc reagents to aldehydes. Similar to the analogous homogeneous systems, dual stereocontrol in addition products can be achieved by controlling the stoichiometry of the immobilized nickel complex. Aromatic and aliphatic aldehydes were alkylated in good yields with enantioselectivities comparable to those obtained with the homogeneous analogues. These polymer-supported catalysts offer significant advantages as no metal leaching is observed and they can be easily recovered from the reaction mixture by simple filtration and…

Quality of Life in Patients Rehabilitated with Implant-Supported Prostheses – A Systematic Review

2021

Abstract Oral health-related quality of life can be defined as the perception of the impact that oral health has on the quality of life. The quality of life is characterized by a person’s perception of his/her social status and the activities he/she carries out in daily life, in relation to his/her standards, objectives, concerns and expectations, as well as the system of values and cultural conditions within he/she lives in. Objective: The objective of this study was to systematically review the dental literature to identify and classify relevant articles on the quality of life associated with the oral health of patients rehabilitated with implant-supported prostheses. Materials and method…