Designed Synthesis of 3D Covalent Organic Frameworks El-Kaderi, Hani M; Hunt, Joseph R; Mendoza-Cortés, José L ...
Science (American Association for the Advancement of Science),
04/2007, Letnik:
316, Številka:
5822
Journal Article
Recenzirano
Three-dimensional covalent organic frameworks (3D COFs) were synthesized by targeting two nets based on triangular and tetrahedral nodes: ctn and bor. The respective 3D COFs were synthesized as ...crystalline solids by condensation reactions of tetrahedral tetra(4-dihydroxyborylphenyl) methane or tetra(4-dihydroxyborylphenyl)silane and by co-condensation of triangular 2,3,6,7,10,11-hexahydroxytriphenylene. Because these materials are entirely constructed from strong covalent bonds (C-C, C-O, C-B, and B-O), they have high thermal stabilities (400° to 500°C), and they also have high surface areas (3472 and 4210 square meters per gram for COF-102 and COF-103, respectively) and extremely low densities (0.17 grams per cubic centimeter).
Porous, Crystalline, Covalent Organic Frameworks Côté, Adrien P; Benin, Annabelle I; Ockwig, Nathan W ...
Science (American Association for the Advancement of Science),
11/2005, Letnik:
310, Številka:
5751
Journal Article
Recenzirano
Covalent organic frameworks (COFs) have been designed and successfully synthesized by condensation reactions of phenyl diboronic acid {C₆H₄B(OH)₂₂} and hexahydroxytriphenylene C₁₈H₆(OH)₆. Powder ...x-ray diffraction studies of the highly crystalline products (C₃H₂BO)₆·(C₉H₁₂)₁ (COF-1) and C₉H₄BO₂ (COF-5) revealed expanded porous graphitic layers that are either staggered (COF-1, P6₃/mmc) or eclipsed (COF-5, P6/mmm). Their crystal structures are entirely held by strong bonds between B, C, and O atoms to form rigid porous architectures with pore sizes ranging from 7 to 27 angstroms. COF-1 and COF-5 exhibit high thermal stability (to temperatures up to 500° to 600°C), permanent porosity, and high surface areas (711 and 1590 square meters per gram, respectively).
Zeolitic imidazolate frameworks (ZIFs) are porous crystalline materials with tetrahedral networks that resemble those of zeolites: transition metals (Zn, Co) replace tetrahedrally coordinated atoms ...(for example, Si), and imidazolate links replace oxygen bridges. A striking feature of these materials is that the structure adopted by a given ZIF is determined by link-link interactions, rather than by the structure directing agents used in zeolite synthesis. As a result, systematic variations of linker substituents have yielded many different ZIFs that exhibit known or predicted zeolite topologies. The materials are chemically and thermally stable, yet have the long-sought-after design flexibility offered by functionalized organic links and a high density of transition metal ions. Here we report the synthesis and characterization of two porous ZIFs-ZIF-95 and ZIF-100-with structures of a scale and complexity previously unknown in zeolites. The materials have complex cages that contain up to 264 vertices, and are constructed from as many as 7,524 atoms. As expected from the adsorption selectivity recently documented for other members of this materials family, both ZIFs selectively capture carbon dioxide from several different gas mixtures at room temperature, with ZIF-100 capable of storing 28 litres per litre of material at standard temperature and pressure. These characteristics, combined with their high thermal and chemical stability and ease of fabrication, make ZIFs promising candidate materials for strategies aimed at ameliorating increasing atmospheric carbon dioxide levels.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
This paper reports the synthesis and characterization of a new crystalline 3D covalent organic framework, COF-202: C(C6H4)43B3O6 ( t BuSi)24, formed from condensation of a divergent boronic acid, ...tetra(4-dihydroxyborylphenyl)methane, and tert-butylsilane triol, t BuSi(OH)3. This framework is constructed through strong covalent bonds (Si−O, B−O) that link triangular and tetrahedral building units to form a structure based on the carbon nitride topology. COF-202 demonstrates high thermal stability, low density, and high porosity with a surface area of 2690 m2 g−1. The design and synthesis of COF-202 expand the type of linkage that could be used to crystallize new materials with extended covalent organic frameworks.
IMPORTANCE: Vasopressin is an alternative to catecholamine vasopressors for patients with distributive shock—a condition due to excessive vasodilation, most frequently from severe infection. Blood ...pressure support with a noncatecholamine vasopressor may reduce stimulation of adrenergic receptors and decrease myocardial oxygen demand. Atrial fibrillation is common with catecholamines and is associated with adverse events, including mortality and increased length of stay (LOS). OBJECTIVES: To determine whether treatment with vasopressin + catecholamine vasopressors compared with catecholamine vasopressors alone was associated with reductions in the risk of adverse events. DATA SOURCES: MEDLINE, EMBASE, and CENTRAL were searched from inception to February 2018. Experts were asked and meta-registries searched to identify ongoing trials. STUDY SELECTION: Pairs of reviewers identified randomized clinical trials comparing vasopressin in combination with catecholamine vasopressors to catecholamines alone for patients with distributive shock. DATA EXTRACTION AND SYNTHESIS: Two reviewers abstracted data independently. A random-effects model was used to combine data. MAIN OUTCOMES AND MEASURES: The primary outcome was atrial fibrillation. Other outcomes included mortality, requirement for renal replacement therapy (RRT), myocardial injury, ventricular arrhythmia, stroke, and LOS in the intensive care unit and hospital. Measures of association are reported as risk ratios (RRs) for clinical outcomes and mean differences for LOS. RESULTS: Twenty-three randomized clinical trials were identified (3088 patients; mean age, 61.1 years 14.2; women, 45.3%). High-quality evidence supported a lower risk of atrial fibrillation associated with vasopressin treatment (RR, 0.77 95% CI, 0.67 to 0.88; risk difference RD, −0.06 95% CI, −0.13 to 0.01). For mortality, the overall RR estimate was 0.89 (95% CI, 0.82 to 0.97; RD, −0.04 95% CI, −0.07 to 0.00); however, when limited to trials at low risk of bias, the RR estimate was 0.96 (95% CI, 0.84 to 1.11). The overall RR estimate for RRT was 0.74 (95% CI, 0.51 to 1.08; RD, −0.07 95% CI, −0.12 to −0.01). However, in an analysis limited to trials at low risk of bias, RR was 0.70 (95% CI, 0.53 to 0.92, P for interaction = .77). There were no significant differences in the pooled risks for other outcomes. CONCLUSIONS AND RELEVANCE: In this systematic review and meta-analysis, the addition of vasopressin to catecholamine vasopressors compared with catecholamines alone was associated with a lower risk of atrial fibrillation. Findings for secondary outcomes varied.
Zeolite A imidazolate frameworks Hayashi, Hideki; Yaghi, Omar M; Côté, Adrien P ...
Nature materials,
07/2007, Letnik:
6, Številka:
7
Journal Article
Recenzirano
Faujasite (FAU) and zeolite A (LTA) are technologically important porous zeolites (aluminosilicates) because of their extensive use in petroleum cracking and water softening. Introducing organic ...units and transition metals into the backbone of these types of zeolite allows us to expand their pore structures, enhance their functionality and access new applications. The invention of metal-organic frameworks and zeolitic imidazolate frameworks (ZIFs) has provided materials based on simple zeolite structures where only one type of cage is present. However, so far, no metal-organic analogues based on FAU or LTA topologies exist owing to the difficulty imposed by the presence of two types of large cage (super- and β-cages for FAU, α- and β-cages for LTA). Here, we have identified a strategy to produce an LTA imidazolate framework in which both the link geometry and link-link interactions play a decisive structure-directing role. We describe the synthesis and crystal structures of three porous ZIFs that are expanded analogues of zeolite A; their cage walls are functionalized, and their metal ions can be changed without changing the underlying LTA topology. Hydrogen, methane, carbon dioxide and argon gas adsorption isotherms are reported and the selectivity of this material for carbon dioxide over methane is demonstrated.
Fluorescent detection in cells has been tremendously developed over the years and now benefits from a large array of reporters that can provide sensitive and specific detection in real time. However, ...the intracellular monitoring of metabolite levels still poses great challenges due to the often complex nature of detected metabolites. Here, we provide a systematic analysis of thiamin pyrophosphate (TPP) metabolism in Escherichia coli by using a TPP-sensing riboswitch that controls the expression of the fluorescent gfp reporter. By comparing different combinations of reporter fusions and TPP-sensing riboswitches, we determine key elements that are associated with strong TPP-dependent sensing. Furthermore, by using the Keio collection as a proxy for growth conditions differing in TPP levels, we perform a high-throughput screen analysis using high-density solid agar plates. Our study reveals several genes whose deletion leads to increased or decreased TPP levels. The approach developed here could be applicable to other riboswitches and reporter genes, thus representing a framework onto which further development could lead to highly sophisticated detection platforms allowing metabolic screens and identification of orphan riboswitches.
The Virgo Environmental Survey Tracing Ionised Gas Emission (VESTIGE) is a blind narrow-band (NB) Hα+NII imaging survey carried out with MegaCam at the Canada–France–Hawaii Telescope. The survey ...covers the whole Virgo cluster region from its core to one virial radius (104 deg2). The sensitivity of the survey is of f(Hα) ~ 4 × 10−17 erg s−1 cm−2 (5σ detection limit) for point sources and Σ(Hα) ~ 2 × 10−18 erg s−1 cm−2 arcsec−2 (1σ detection limit at 3 arcsec resolution) for extended sources, making VESTIGE the deepest and largest blind NB survey of a nearby cluster. This paper presents the survey in all its technical aspects, including the survey design, the observing strategy, the achieved sensitivity in both the NB Hα+NII and in the broad-band r filter used for the stellar continuum subtraction, the data reduction, calibration, and products, as well as its status after the first observing semester. We briefly describe the Hα properties of galaxies located in a 4 × 1 deg2 strip in the core of the cluster north of M87, where several extended tails of ionised gas are detected. This paper also lists the main scientific motivations for VESTIGE, which include the study of the effects of the environment on galaxy evolution, the fate of the stripped gas in cluster objects, the star formation process in nearby galaxies of different type and stellar mass, the determination of the Hα luminosity function and of the Hα scaling relations down to ~106 M⊙ stellar mass objects, and the reconstruction of the dynamical structure of the Virgo cluster. This unique set of data will also be used to study the HII luminosity function in hundreds of galaxies, the diffuse Hα+NII emission of the Milky Way at high Galactic latitude, and the properties of emission line galaxies at high redshift.
Twelve zeolitic imidazolate frameworks (ZIFs; termed ZIF-1 to -12) have been synthesized as crystals by copolymerization of either Zn(II) (ZIF-1 to -4, -6 to -8, and -10 to -11) or Co(II) (ZIF-9 and ...-12) with imidazolate-type links. The ZIF crystal structures are based on the nets of seven distinct aluminosilicate zeolites: tetrahedral Si(AI) and the bridging O are replaced with transition metal ion and imidazolate link, respectively. In addition, one example of mixed-coordination imidazolate of Zn(II) and In(III) (ZIF-5) based on the garnet net is reported. Study of the gas adsorption and thermal and chemical stability of two prototypical members, ZIF-8 and -11, demonstrated their permanent porosity (Langmuir surface area = 1,810 m²/g), high thermal stability (up to 550°C), and remarkable chemical resistance to boiling alkaline water and organic solvents.
In October 2017, a partnership was established between the University Hospital of Toulouse and the French Chiropractic College, "Institut Franco-Européen de Chiropraxie" (IFEC). Before 2017, ...chiropractors did not practice in hospitals in France. Chiropractic students and chiropractors are now integrated in an interdisciplinary medical team at University Hospital. Our study aimed to describe the characteristics of patients who received chiropractic care at the University Hospital of Toulouse, their expectations, experiences of care, and satisfaction.
A prospective case study was conducted. Patients referred for chiropractic care in the French University Hospital of Toulouse from January to December 2020 were eligible to participate. Participants provided the following data: demographics, previous chiropractic care treatments, pain location, intensity (NRS) and duration, disability (NDI, ODI), health-related quality of life (SF-12) and depressive symptomatology (PHQ-9). We conducted semi-structured interviews to explore their expectations, barriers and facilitators impacting their experience of care, and satisfaction.
Seventeen participants were recruited and seven were interviewed. All participants had chronic pain with a median pain intensity of 05/10 (IQR 04-06) on the NRS scale. Nine of 17 participants presented with multiple pain locations. Thirteen of seventeen participants presented with low back pain and eight with neck pain. The median SF-12 health-related quality of life score was 50/100 (IQR 28.5-60.5) for physical health, and 52/100 (IQR 43-62) for mental health. The PHQ-9 median score of depressive symptomatology was 7.7/27 (IQR 2.0-12.5). Overall, participants were satisfied with their care and the collaboration between chiropractors and physicians. Participants expected a caring communication with the chiropractic team. Their experience was facilitated by their trust in their physician. Patients perceived the turnover of chiropractic students as a barrier to their satisfaction.
Our participants presented with chronic musculoskeletal pain and depressive symptoms. Our study identified facilitators and barriers for patient expectation and satisfaction with chiropractic care in a hospital setting. This study provides the first data describing the collaboration between chiropractors and physicians in France in the management of musculoskeletal disorders. These findings will inform the quality improvement of our partnership, student's training and the development of future hospital-based collaborations integrating chiropractic care in a multidisciplinary team in France.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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